University of Nigeria Research Publications
SAMUEL, Baba Onoja
Aut
hor
PG/M Eng/89/5409
Title
University of Nigeria Nsukka (UNN)
Wastewater as Irrigation Water Source: Its Suitability and its Effects on Soil and Crop
Facu
lty
Agriculture
Dep
artm
ent
Agricultural Engineering
Dat
e
November, 1989
Sign
atur
e
Sa-nuel 3359 Onoja , a P o s t g r a a u a c e scuaeac i n s n e
Depar txen t of A g r i c u l t u r a l Z n g i n ~ e r i n g an? with
the Reg. 210 PG/:d.3ng/37/5409 has sa t i s f a z t o r i l y
c o n p l e t e 4 the r e q u i r e z e n t s f o r the coursa and
r e s e a r c h work f o r t h e degree o f Xastar of
and has n o t Seen su5nittzd in c z r t o r fall f2r m y
o t h e r di?lorna o r d a g r s e o f t h i s o r any otisr
Supervisor Superv I ' s o r
E x t e r n a l Exan ine r
D Z D I C A T I O N
The o n l y x i s ? God;
tat he^, Son and 3oly S p i r i t . r
Ynom to Zear i s x i sdoa
indeed.
iii.
I acknowledge t h e i n c e n s e c o n t r i b u t i o n of m y s u p e r v i s o r s :
Zngr (Dr ) 7.1. I d i k e and D r . G.O. Ch-dwuca f o r a p p r o g r i a t e
a d v i c e , encouragement and s u g ? o r t th rov~ghout t h e c o u r s e o f
t h i s work. I acknowledge t h e i n t e r - d e p a r t m e n t a l c ~ m n ~ i c a t i o n
acd a l s o t k a d i f f e r e n t c o n t r i h l t l o n s f r z a a n u b a r of t h e
acadein ic , t e c h n i c a l and a d o i n i s t r a t i v e s t a f i o f t h e Dep2r tnan t .
The i n t ? r - d i s c i p l i n a r y ~ s t u r 9 of t3is study made it
' c a n n o t be a a n t i o n e d h s r e . I ackro:tledga the a p g r e v a l g r a n t e d - -
n e by t h e Heads o f D e ? a r t n e n t s o f C i v i l S n g i n o e r i n g , S o i l
S c i e n c e and Crop S c i e n c e f o r t h e use of their l a b o r a t o r i e s .
I a m g r a t e f u l t o D r s B.N. Mbah, B.B. Fakae , 0. Onof iok and
C.P.E. Ornaliko f o r t h e i r i n d i v i d u a l c o n t r i b u t i o n s . I
acknowledge t h e c o - o p e r a t i o n and a s s i s t a n c e o f Mr. Ongeokoro
a n d h i s t e a n of staff a t the U n i v e r s i t y of N i g e r i a , Nsukka
Sewage T r e a t m e n t works; the l a b o r a t o r y and f i e l d a s s i s t a n c e o f
Messrs N. 'dogu, E. Udea la , S.E. Ani, C.J. O n y i r i o h a , U. Umeh,
C.E.O. ~ e b o ; E.O. E l e r i , M.O. Agbahiwe and A. Ezernah and t h e . .
good t y p i n g work done by Mrs Nkechi Okpala.
iv.
I am e q u a l l y i n d e b t e d t o a number of r e l a t i o n s , f r i e n d s
and c h r i s t i a n b r e t h r e n f o r mora l , f i n a n c i a l and p r a y e r
s u p p o r t . I a l s o acknov ledgs t h e f i n a n c i a l a s s i s t a n c e from
s p s c i f i c i n d i v i d u a l s l o r t h e p u r p o s e of t h e e n t i r e programs.
l i n a l l ~ , I a c ! m o v l a d ~ a and a p p r e c i a t e t h e f u l l s u g s o r t
of 3y w i f e Xr3 2ode 3ab3 Ooojs and t h e p a t i e n c e of t h e f a z i l y
f o r t h e p e r i o d c f t h i s X a s t e r I s d?grae progranme.
T h a n k s and m y God reward yo11 a l l , .Anzn.
U n i v e r s i t y o f N i g e r i a , Nsukka (UN, Nsukka Campus) w a s t e w a t e r
t r e a t m e n t works as i r r i g a t i o n w a t e r s o u r c e . F i e l d and
\
l a b o r a t o r y e x a m i n a t i o n s were c a r r i e d o u t t o e v a l u a t e t h e
w a s t e w a t e r c h a r a c t e r i s t i c s , t h e p h y s i c a l and c h e m i c a l p r o p e r -
t i e s of t h e s o i l a n d t h e m i n e r a l c o m p o s i t i o n o f wal3tcwater
i r r i g a t e d a m a r a n t h u s SPP.
The r e s u l t s o f t h e s t u d y show t h a t w h i l e w a s t e w a t e r f rom
pond 2 o f t h e t r e a t m e n t works is s u i t a b l e for i r r i g a t i o n , t he
i n f l u c n t and the w a s t e w a t e r i n pond I n r e t o o p o l l u t c d t o s e r v e
as i r r i g a t i o n w a t e r s o u r c e . Wastewater i r r i g a t i o n i n t h e s t u d y
s i t e improved t h e w a t e r h o l d i n g c a p a c i t y of t h e s o i l a n d
i n c r e a s e d i t s c h e m i c a l p r o p e r t i e s i n t h e o r d e r of o v e r 200% f o r
E-Ce 'and 1 3 ~ ; o v e r 100Y f o r N , P a n d Ca, 92% f o r CEC, 45% f a r K
and 675 f a r Na; b u t d e c r e a s e d t h e s a i l pH, SAR and ESP by 5%,
17.5; a n d ~87.? r c s p e c t i v e l y . Wastewntcr a p p l i e d an i r r i g a t i o n
w a t e r was a l s o found t o c o n t r i b u t e e s s e n t i n l m i n e r a l s n o t o n l y
t o t h e s o i l b u t a l s o to t h e c rop . C o n s e q u e n t l y t h e p r a c t i c e ,of
w a s t e v g t c r i r r i g a t i o n is recommended as a s o i l improvement
p r a c t i c e .
Rased on t h e r e s u l t s o f t h e s t u d y , recommendat ions f o r
f u r t h e r s t u d i e s and f o r t h e management a n d u s e o f w a s t e w a t e r as
i r r i g a t i o n w a t e r i n t h e g e n e r a l l o c a l i t y o f t h e s t u d y s i t e a r e
p r e s e n t e d ,
Content P a g e
CHAPT3R 111: ?!ATERIALS AND METHODS - w e o
I : The Zxper imenta l Area .a. . e O - . o
2 2 v s l u a t i o n of w a s t e x a t e r c k a r a c t e r i s t i c s . . 3.2: Sam?ling positions and f requency ... ... 3.2.2: L z j o r a t o r y T a s t s ... .-. -.. 3 . 3 Z v a l u a t i n g the E f f e c t o f v a s t e w a t e r
I r r i g a t i o n o n s a i l progert i e s . S O ... 3.4: 3raLsating t h e E f f e c t o f w a s t e x a t e r
Irrigation on t h e I r r i g a t e d vege tab le (Xx3ranthus SP?. ) ... ... ..,
3.4.1 : San?linq ... ... . . - ... t ,.-r.2: n. bile " i c e r a l Inal;7sis cf v e s e t s j l s s a 3 ? l e s ,
Vas5exa te r c h a r a c t e r i s t i c s .-a ... 61 S o i l g r o g e r t i e s ... ... . . . 6 9
The p h y s i c a l p r o p e r t i e s o f t h e s o i l .ma 69 ... C t e z t c s l - - ~ r o z e r t i e s of t h e s a i l ... '7 3 T?--5 ninersl coa?osition of leaves of ... Xca~c..Stus S?? . I . 6.e .-- 73
'3 : DISSCSS I C Y ... ... . . . 77 -.-
5.1: m & u a l i t y o f t h e University o f ' l lgeria, P7sukka (UE?;) !Jaaterater for I r r i g a t i o n ... 7 7 &'ze e f f ~ c t s 5.2: o f wastewater I r r i g a t i o n 02 s o i l p r o p e r t i e s .-. ... ... 33
5.2.1: E f f e c t s on t h e P h y s i c a l p r o p e r t i s s o f t h e s o i l .-• o . . ..- - 0 - 83
5.2.2: E f f e c t s o n t h e chemical p r o p e r t i e s of t h e s o i l . a m . - . a = . ... 85
- 5.3: E f f e c t of wastewater on some of the mineral constituents of Amaranthus SPP. v e g e t a b l e l e a v e s ... ... ... 88
.CHAPTYR V I : CONCLUSION AND RECOMMENDATIONS ... 91
S e f e r e n c e s ... ..a .-• ..- 97
v i i i .
LIST OF TABLES
Table
Recommended maximum c o n c e n t r a t i o n s o f t r a c e ... e l e m e n t s i n i r r i g a t i o n water ... . o m
C o n d i t i o n s f o r s a l i n e , s a l i n e - a l k a l i and ... a l k a l i s o i l s ... ... ... ... Limi ' ts o f boron i n i r r i g a t i o n w n t o r For s e n s i t i v e , s e m i - t a l c r a n t a n d t o l e r a n t s p e c i e s based on t o x i c i t y symptoms o b s e r v e d on p l a n t s grown i n s a n d c u l t u r e .,, . . 0 . . ..*
Physical, Chemical and B i o l o g i c a l c h a r a c t e r i s t i c s of vrastevrat e r ..* .-• ... ...
\
T y p i c a l s a n i t a r y c h e m i c i l ? a n a l y s i s o f sewage ... ( Q u a l i t y o f domes t i c w a s t e ) . . . . . C a l i f o r n i a S t a t e Department o f R e n l t h s t a n d a r d s f o r t h e s a fe and d i r e c t u s e o f r e c l a i m e d waste- water f a r i r r i g a t i o n and r e c r e a t i o n a l ... impoundments -., ... . . . ... VIIO s u ~ g e s t e d t r e a t m e n t p r o c e s s e s t o meet t h e givcn h e a l t h c r i t e r i a f o r was tewate r r e u s e
l-lcthods for the examina t ion of was tewate r samples ... . . . - 1 0 ... Sampling s c h e d u l e o f t h e w a s t e w a t e r f a r examinat i o n ... ... ... . . . Site s e l e c t i o n f o r s o i l a n a l y s i s ... 1~Icthod.s used f o r t h e d c t c r m i n a t i o n o f s o i l p r o p e r t i c s . . ... ... . rn Methbds used f o r t h e chemical a n a l y s i s o f hnrnrnnthus SPP, leaves a * e m e ,
P a g e
12
t a l s o l i d s of een Cecenber 1988 * 0 . . . . ..a
P-- ~ - - , - , - ~ s l 5-: ,- propertils of soil f r o 3 e i g h t l o c a t i o n s i r r i z a t e d w i t h wastewater compared w i t h IX soil smp133 f r c n an a 2 j a c e n t a r e a ... . .. Xean a ~ d s t a c d a r d d e v i a t i o s of s o i l c h e n i c a l p r o p e r t i s s a s influezced 37 sewage t r e a t a e n t .., X i n e r a l c o n t e n t s o f l e a v e s of amaranthus SP? grown on soils i r r i g a t e d with t h e wastewater and with ordinary water . .. . m e ... o m -
Ths e f f e c t of treatment was teua te r l o c a t i o n and tap water on t h e chenica l composit ion of =aranthus l eaves , DXTIRT . .* @ . 0 . .
B l e ~ e n t s with statistical differences between t a p wate r and t h e d i f f e r e n t l o c a t i o n s o f wastewater ... a * - -.. 0 . . .-. ~ o a c e n t r a t i o n s of t h e e s s e n t i a l macro- a u t r i e n t a o f t h e wastewater i r r i g a t e d and n o n - i r r i g a t s d a r e a s . . . ... . . . ...
X.
LIST OF FIGUXS
1. .Concent ra t io .? o f i r r i p t i o n w a t e r s r e l a t e d t o c o n d u c t i v i t y ... . -. ...
2 . U53X c l a s s e s of S a l i n i t y and Sodiun h a z a r d f o r I r r i g a t i o n water . . . ...
3. S c h ? n s t i c d i a g r a n o f s ampl ing ? o i n t s o r l o c a t i o n s f a r w a s t e w a t e r , s o i l aad c r 0 ? ... ... . . . ... ...
4. P r e p a r e d c o ~ r u g a t i o r i s resdy f o r a n a r m t b n s s e e d l i n g ... . . . . . ...
Sa & b Viexs o f s i t e d u r i n g t h e psak p e r i o d of amaran ths3 c u i t i v a t i o n ... . . . . ..
6a & ?I Vieus of s i t e a t t h e o n z e t o f r a i n y s e a s a c c r a g ~ i z g . . . ... ...
7. :locoi;raa f o r d e t e r n i n i x g t h e SX?, v a l u e of I r r i p t i o n v a t e r and f o r e s t i m a t i n g t h e c o r r e s p o n d i z g ZSP v a l u e o f a s o i l e q u i l i b r a t e d w i t 3 t h i s w a t e r . . . ... . . . 54
8. Aaarai i thca 522 grown i n t h e study a r e a and i r r i g a t e d w i t h o n l y p o t a b l e ta? w a t e r . .. 59
-. x i .
SPP
5 d a y b i o c h e n i c a l oxygen denand
Calc i urn
C a t i o a exchange c a ~ a c i t y
Duncan 3ew N u l t i p l e Ban35 Test
E l 2 c t r i c a l C o n d x c t i 7 l t y
3xc3aagsaSle sodium p e r c e n t age
P i e l d c a p s c i t y
P o t a s s i m
X a p e s s i u a
Xi t r o g l n
Sodium
Phosshorus
S o d i u Adsorp t ion ratio
S p e c i e s
p r o d u c t i o n i; s u p p l i e d a r t i f i c i a l l y . It i s scg?lexeatal
ar- $0 3e 7roduced t o z k e t . m n ' s n e e d f o r f o o d a n d f i b r e .
persons 324 5" ecro? prodxczd as i f e l l as
' L using it 1s irrigation
f u n c t j o n o f climatic f a c t o r s ; quantity o f v 8 t e r uzed Sy t h e
c o n s i d s r z i l l y redaced. The e f f l u e z t f r o a t h e s t a b i l i z a t i o n
?or .h 1; s - ~ ~ - z s s e d A - t o Se s a f e f o r d i s 2 3 s s l acd t h e f i c a l
long t h b e f f l u e n t c o u r s e d u r i n q t h e d r y s e a s o n (::oveab.2r - Februarg/>!nrch) . No d i s c r i m i n a t i o n is made a s t o xhnt saints
o f t h e p o n d s s h o u l d be u s e d as i r r i g a t i o n w a t e r . The m a j o r
c r o p i r r i g a t e d d u r i n g t h i s s e a s o n i s t h e v e g e t a b l e ,
a m a r a n t h u s s p e c i e s .
T h i s s t u d y i s aimed a t a s s e s s i n g t h e c u r r e n t u s e o f t h e
U n i v e r s i t y o f N i g e r i a , Nsukka (U.N.N.) w a s t e v a t e r a s i r r i g a t i o n
w a t e r s o u r c e a n d g e n e r a t i n g p e r t i n e n t i n f o r m a t i o n o n ,waste-
w a t e r i r r i g a t i o n i n Nsukka a n d i n a r e a s w i t h s i m i l a r c o n d i t i o n s
and f a c i l i t i e s . The s p e c i f i c o b j e c t i v e s o f t h e s t u d y i n c l u d e
(i) To i n v e s t i g a t e t h e s u i t a b i l i t y o f t h e
U n i v e r s i t y o f N i g ; r i a , Nsukka w a s t e w a t e r
as i r r i g a t i o n w a t e r ,
( i i ) To d e t e r m i n e t h e e f f e c t s o f p r o l o n g e d
w a s t e w a t e r i r r i g a t i o n on t h e p h y s i c a l and
c h e m i c a l p r o p e r t i e s o f t h e s o i l , and
( i i i ) To d e t e r m i n e t h e e f f e c t s o f w a s t e w a t e r
' i r r i g a t i o n o n t h e n i n e r a l c o m p o s i t i o n o f
i r r i g a t e d a m a r a n t h u s spp . v e g e t a b l e .
p r o d u c t i o n .
2. 2 C ','.2?7E!
2.2.1 S o u r c e s a n d q u a l i t y .
The comnonly a v a i l a b l e s o u r c e s o f water f a r irrigation
l i ! n i t o l , i n c ~ e a s e d u s e is b e i n 3 zade of in! a r i o r quality i r r i g a t i o n
for C It io only t h r o u g h ? r o p e r nacnge "11t b a s e d on i k c
-;..:: . 7 . . . bnductivity (rnicromhos per cm., E.C. X 106, at 25' C)
rig 1: C c s c e c t r a t i o n of i r r i g a t i o n w a t e r s r e l a t e d t o c o n d u c t i v i t y .
. S o u r c e : - I s r a e l s e n a n d 3 a n s e n ( 1 9 6 2 ) .
EC X 10' = Conductivity micrornhos/cm at 25°C
C-1 C-2 C-3 C-4
Low Medium High Very high u I I I I
Salinity hazard
F i g 2 : USDA c l a s s e s o f s a l i n i t y a n d s o d i l n h a z a r d f o r i r r i g a t i o n w a t e r .
b
S o u r c e : - T r o e h e t a1 ( 1 9 8 ~ ) .
Table I. Recommended naximun c o n c e n t r a t i o n s of t r a c e
e l emen t s i n I r r i g a t i o n water 1
Aluminium
Arsen ic
B e r y l l i m
Boron
Cadmium
C h r o z i m
Co5al t
Copper
F l o u r i n e
I r o n
Lead
Li th ium
Manganese
Molybdenum
?lickel
S e l e n i u n
Vanadium
Zinc
F o r w a t e r s used c o n t i n u o u s l y on a l l s o i l ( ~ g / l i t e r )
For use up t o 20 y e a r s on f i n e - t e x t u r e d s o i l s a t pH 6.0 t o 8.5
( m a / l i t e r )
20.0
1. These l e v e l s w i l l n o t normal ly nave an a d v e r s e e f f e c t on ~ l a n t s o r s o i l s . No d a t a a v a i l a b l e f o r mercury, s i l v e r , - . t i n , t i t a n i u m , t u n g s t e r .
2. Recommended maximum c o n c e n t r a t i o n s f o r c i t r u s is 0.75mg/ l i t e r .
3 Only f o r f i n e - t e x t u r e d a c i d s o i l s , o r a c i d s o i l s v i t h I!elat ively h i g h c o n t e c t of I r o n oxide.
Source : S h a i n b e r g and 0 s t e r ( 1978).
13.
2.2.2. E f f e c t s of I r r i g a t i o n 'da ter Q u a l i t y on S o i l P r o p e r t i e s .
The q u a l i t y of i r r i g a t i o n wa te r can adverzzly a f f e c t
s o i l p r o p e r t i e s depending on t h e c o n c e n t r a t i o n s of i t s con-
s t i t u e n t s . G e n e r a l l y , t h e major conce rn i n e v a l u a t i n g
i r r i g a t i o n wa te r i s t h e p o s s i b l e n e g a t i v e e f f e c t s t h a t may
be caused by s a l i n i t y and s o d i c i t y problems. The main f a c t o r s
a r e c o n c e n t r a t i o n of s a l t s i n t h e s o i l s o l u t i o n and t h e n a t u r e
and degree of exchangesble c a t i o n s (Michael , 1978). The
p h y s i c a l and chemical ' p r o p e r t i e s of i r r i g a t e d s o i l s depend
l a r g e l y on t h e chemical compos i t ion of t h e i r r i g a t i o n wa te r ,
s o i l t y p e , d r a i n a g e c h a r a c t e r i s t i c s and t h e c l i m a t i c c o n d i t i o n s .
A s o i l may be s a l i n e , s a l i n e - a l k a l i o r a l k a l i ( s o d i c ) depending
on t h e l e v e l of c o n c e n t r a t i o n of sal t i n the s o i l ( t a b l e 2) .
S a l t c o n c e n t r a t i o n i n t h e s o i l may be caused by t h e q u a l i t y of
i r r i g a t i o n water .
The e f f e c t s of s a l t s on t h e chemica l p r o p e r t i e s of t h e s o i l
i n c l u d e among o t h e r s :
( i ) S a l i n i t y haza rd a s r e c o g n i s e d i n s o i l by t h e
p r e s e n c e of w h i t e s u r f a c e c r u s t s and caused by
e x c e s s i v e s a l t c o n c e n t r a t i o n .
( i i ) . Inc reased exchangeably sodium pe rcen tage caused
by i n c r e a s e i n SAR of i r r i g a t i o n water .
T a b l e 2: C o n d i t i o n s f o r S a l i n e , S a l i n e - A l k a l i a n d A l k a l i
s o i l s .
S a l t Index : - I a l k a l i I I I
A l k a l i ( s o d i c )
B l a c k a l k a l i L
C o n d u c t i v i t y o f S a t u r a t i o n E x t r a c t i n m i l l i m h o r p e r cm
S a l i n e - A l k a l i S a l t C o n d i t i o n
Common Term
Sodium Index :
S a l i n e
' d h i t e
Exchangeab le Sodium p e r c e n t a g e
1
Bydrogen I o n 1ndex :
Reclamat i o n Leach ing
3 e n e r a l l y a b o u t 8 -5
g e n e r a l l y between 8.5 - 10.0
L e a c h i n g n e c e s s a r y and p o s s i b l e , b u t as s a l t s a r e r e - ma-led t h e s o d i u n must be r e p l a c e d t o p r e v e n t d i s - p e r s i o n o f s o i l p a r t i c l e s and r e d u c t i o n o f p e r m e a b i l i t y
Low p e r m e a b i l i t y due t o d i s p e r s i o n o f s o i l by t h e sodium r e q u i r e s r e p l a c i n g t ?e sodium t o i . ? rove t h e p e r m e a b i l i t y s o t h a t l e a c h i n g c a n proceed .
S i n c e a pH of 7.0 i s n e u t r a l , pH v a l u e s l e s s t h a n 7.0 i n d i c a t e a n a:id s o i l which is common i n n o n - a r i d r e g i o n s . Note t h a t t h e l a r g e r t h e pH, t h e l e s s t h e c o n c e n t r a t i o n o f hydrogen i o n s , s i n c e pH i s t h e l o g a r i t h m of t h e r e c i p r o c a l o f t h e hydrogen i o n c o n c e n t r a t i on .
A b l a c k c r u s t fo rms o n t h e s u r f a c e o f Sn a l k a l i s o i l o n l y i f o r g a n i c m a t t e r i s p r e s e n t . Hencz, t h e t e r m may be m i s l e a d i n g i n s o i l s o f low o r g a n i c m a t t e r .
Source : I s r a e l s e n and Hansen (1962).
( i i i ) D e t e r i o r ~ t i o n of s o i l s t r u c t u r e c a u s e d when
more magnessium t h s n c a l c i u m is p r e s e n t i n
i r r i g a t i o n w a t e r . Such i r r i g a t i o n w a t e r may
l i k e l y d e c r e a s e s o i l p r o d u c t i b i t y .
The p h y s i c a l p r o p e r t i e s of s o i l may be a f f e c t e d
p o s i t i v e l y o r a d v e r s e l y i n t h e p r e s e n c e o f s a l t s depend ing
upon t h e n a t u r e a n d amount o f sa l ts , t h e r e a c t i o n p r o d u c t and
t h e i n i t i a l p h y s i c a l and c h e m i c a l c o n d i t i o n s of t h e s o i l . The
main p h y s i c a l p r o p e r t i e s i n f l u e n c i n g t h e a i r - w a t e r r e l a t i o n -
c l a y p a r t i c l e s and p e r m e a b i l i t y of t h e s o i l ( ~ i c h a e l , 1978).
These t x o p r o p e r t i e s a r e a f f e c t e d by s a l t s i n t h e f o l l o w i n g
ways:
( i ) The d e g r e e o f d i s p e r s i o n i n c r e a s e s i n t h e
p r e s e n c e o f e a s i l y d i s p e r s i b l e c l a y w i t h
i n c r e a s e i n sodium s a t u r a t i o n , and d e c r e a s e s
w i t h t h e p r e s e n c e of c e a e n t i n g a g e n t s and s a l t s .
( i i ) The p e r m e a b i l i t y o f s o i l d e c r e a s e s w i t h t h e
i n c r e a s e o f d i s p e r s i b i l i t y and exchangeab l e
sodium p e r c e n t a g e o f t h e s o i l .
I n o t h e r t o p r e d i c t t h e s u c c e s s o f i r r i g a t i o n i n a
p a r t i c u l a r s i t u a t i o n , i t i s e s s e n t i a l t o have a d e q u a t e i n f o r m a t i o n
on t h e q u a l i t y o f i r r i g a t i o n w a t e r , i t s e f f e c t s o n t h e p h y s i c a l
and c h e m i c a l p r o p e r t i e s of t h e s o i l , w a t e r t r a n s m i s s i o n
c h a r a c t e r i s t i c s o f t h e s o i l and sa l t b u i l d - u p i n t h e s o i l .
2.2.3. E f f e c t s o f I r r i g a t i o n ' d a t e r ( q u a l i t y On Croas .
w a t e r The q u a l i t y o f i r r i g a t i o n L c a n a f f e c t c r o p s i n t h e
f o l l o w i n g ways ( X i c h a e l 1978 S h a i n b e r g a n d o s t e r 1978 ) 1
( a ) I n c r e a s e i n o s m o t i c p r e s s u r e i n a s a l i n e s o i l
t h a t c a n r e s u l t f rom t h e u s e o f s a l i n e i r r i g a t i o n
w a t e r and which i n t u r n d e c r e a s e s t h e o s m o t i c
a c t i v i t y o f p l a n t t h e r e b y r e d u c i n g t h e u p t a k e o f
w a t e r and n u t r i e n t s f rom t h e s o i l .
( b ) Accumula t ion o f i o n s i n t o x i c c o n c e n t r a t i o n i n
t h e p l a n t t i s s u e r e s u l t i n g f rom h i g h c o n c e n t r a -
t i o n s o f such i o n s i n t h e s o i l s o l u t i o n . T h i s
c a n d e p r e s s c r o p groswth and y i e l d .
( c ) Accumula t ion o f one o r more n u t r i e n t s i n e x c e s s
amounts which may be a t t r i b u t a b l e t o t h e i r r i g a -
t i o n w a t e r , i n h i b i t s t h e u p t a k e o f o t h 2 r e s s e n t i a l
n u t r i e n t s . T h i s c3n a l t e r t h e p l a n t ' s m i n e r a l
n u t r i t i o n a l c h a r a c t e r i s t i c s .
( d ) Aeavy m e t a l s i n i r r i g n t i o n w a t e r t h o u g h immob i l i z ed
i n t h e s o i l can be t a k e n up by t h e p l l n t s . They
a r e o f t e n t o x i c t o t h e p l a n t s , and c a n have t o x i c
e f f e c t on t h e human consune r . D i f f e r e n t c r o p s ,
however have d i f f e r e n t t o l e r a n c e s t o t h e heavy
m e t a l s as known i n t h e c a s e o f b o r a n ( t a b l e 3)
A 1 1 o f t h e above e f f e c t s a r e g e n e r a l l y m a n i f e s t 2 d i n poor
s t a n d s o f c r o p , s t u n t e d growth and r e d u c e d y i e l d . O t h e r e f f e c t s
may i n c l u d e l e a v e b u r n s a l o n g t h e marg in o r t i p i n some c r o p s
T a b l e 3: L i a i t s of boron i n i r r i g a t i o n w a t e r f o r
s e n s i t i v e , s e a i - t o l e r a n t and t o l e r a n t s 2 a c i e s
b ~ s e d on t o x i c i t y symptoms o b s e r v e d on p l m t s
grown i n s a n d c u l t u r e .
S e n s i t i v e 0.3 - I pprn b o r o n - -
C i t r u s
Avocado
A p r i c o t
P e a c h
C h e r r y
Persimmon
F i g
Grape
Apple
P e a r
P l u a
Navy be a n
J e r u s a l e m a r t i c h o n e
Yalnu t
Semi - t o l e r a n t 1 - 2 ppm b o r o n
Lima bean
Sweet p o t a t o
B e l l p e 9 p e r
Cat
Milo
Corn
'dhe a t
B a r l e y
O l i v e
F i e l d pea
Radish
Tomato
C o t t o n
P o t a t o
Sunf l o u e r
T o l e r a n t 2 - 4 ppm bo ron
C a r r o t
L e t t u c e
Cabbage
T u r n i p
Onion
Bread bean
A l f a l f a
Garden b e e t
Mange1
S u g a r b e e t
Palm
Aspa ragus
I n each g r o u p t h e c r o p s a r e arran;e? i n d e s c e n d i n g
o r d e r of t o l e r a n c e w i t h i n t h e r a n g e i n d i c a t e d .
S o u r c e : S h a i n b e r g a n d O s t e r ( 1978).
and deep b l u e g reen c o l o u r s i n o t h e r s . I n some c a a z s
symptoms of e x c e s s i v e s a l t s a r e s i m i l a r t o t h o s e of drought
o r low f e r t i l i t y s t a t u s . S o i l s a l i n i t y c a u s e s a dec rease
i n t h e s i z e and v i g o u r of t h e p l a n t . The ge rmina t ion of
s e e d s c a n be d e l a y e d and r e t a r d e d and t h e c r o p growth p e r i o d
may a l s o be s l i g h t l y reduced. Herbaceaus c r o p s such as
maize, cowpea and amaranthus growing on s a l i n e s o i l s may have
b a r r e n s p o t s , s t u n t e d g r o w t h and deep-blu ish-green f o l i a g e .
E a c r o s i s and dcf ~liaticn z r a also ind4 A b a b l v e --' ' of s a l i n i t y . A
r e d u c t i o n i n y i e l d may occur wi thou t any v i s i b l e symptoms of
s a l t i n j u r y s u c h a s r o o t c rops . T h i s is a l s o t r u e where a
s u l p h a t e - i n d u c e d ca l c ium d e f i c i e n c y may cause t o t a l c rop
f a i l u r e i n toma toes due t o blossom-end r o t , and i r . l e t t u c e due
t o i n t e r n a l brawning.
19
2 .3 W A S T Z ' d X T i R .
I S o u r c c s and c h a r z c t e r i s t i c s of 'dzistewater.
Yas t ewa te r a l s o c a l l e d sewage is s p e n t w a t e r supp ly
from a coinmunity ( P f a f f l i n and Z i e g l e r , 1976) S c a t e t a 1
(1981) d e f i n e was t ewa te r a s t h e wa te r s u p p l y from a community
a f t e r i t h a s been used, Uas tewater i s 99.95% wa te r and
0.05% waskes ( P f a f f l i n and Z i e g l e r , 1976). Although s o u r c e s
of was t ewa te r a r e a s v a r i e d a s t h e u s e s o f w a s t e v a t e r , t h e
major s o u r c e s nag be c l s s s i f i z d 2 s :
( i ) Dumestic was tewater which i n c l u d e s t h o s e from
t h s k i t c h e n , t o i l e t , b a t h , l a u n d r y , e t c .
( i i ) I n c u s t r i a l was tewater from b o t t l i n g companies ,
b r e . ~ e r i e s , chemica l i n d u s t r i e s e t c .
( i i i ) A g r i c u l t u r a l w a s t e v a t e r such as unused i r r i g a t i o n
w a t e r , a g r i c u l t u r a l l a n d r u n o f f .
( i v ) Urban s torm r u n o f f .
' dha tever t h e s o u r c e , was tewater c o n t a i n t h e was te of a
c i t y and i t s i n h a b i t a n t s . By v i r t u e o f h a v i n g been used ,
was t ewa te r h a s p h y s i c a l , chemica l and b i o l o g i c a l c h a r a c t e r i s t i c s
o r compos i t i on t h a t a r e d i f f e r e n t from t h o s e o f t h e o r i g i n a l
~ o k t a b l e w a t e r . The c o n t e n t s of w a s t e ~ a t e r depend main ly on
t h e compos i t i on of t h e water s u p p l y , t h e use t o which t h e wa te r
w a s pu t and t h e method of c o l l e c t i o n . The c o n c e n t r a t i o n s of
t h e different c s n s t i t u e n t a depend on t h e amount of w a t e r
used p e r capita and t h i s z a o u n t is u s u a l l y s m a l l e r i n - _ d e v e l o p i n g c o u n t r i e s a n d i n a r i d and semi -a r id c l i m a t e s
( S h u v a l e t a l , 1986). T a b l e 4 g i v e s t h e p h y s i c a l , chemica l
and b i o l o g i c a l c h a r a c t e r i s t i c s o f was tewater . Depending on - -
t h e compos i t i on o f t h e s e c h a r a c t e r i s t i c s , was tewater can be
c l a s s i f i e d as s t r o n g , medium o r weak ( t a b l e 5 ) f o r t h e c a s e
of domes t i c sewage.
The c o n s t i t u e n t s - , - of domes t i c and i n d u s t r i a l waste-
w a t e r s t h a t a r e s i g n i f i c a n t i n w a t e r p o l l u t i o n c o n t r o l ,
d i s p o s a l and r e u s e i n c l u d e :
(a) S o l u b l e o r g a n i c m a t e r i a l s r e s u l t i n g i n d i s s o l v e d
oxygen d e p l e t i o n i n s t r e a m s , and e s t u a r i e s and o r
c a u s i n g t a s t e a n d odour , i n
( b ) Organ ic suspended s o l i d s r e s u l t i n g / d i s s o l v e d - oxygen d e p l e t i o n ,
( c ) i n e r t suspended s o l i d s c a u s i n g t u r b i d i t y and
r e s u l t i n g i n s e d i m e n t s ,
( d ) t o x i c s u b s t a n c e s and heavy m e t a l i o n s ,
( e ) o i l and f l o a t i n g m a t e r i a l s ,
- ( f ) k c i d s and a l k a l i s and . .
(g) d i s s o l v e d sal ts .
a t e r Source Phys ica l
S o l i d s Carr iage water,. domeetic and i n d u s t r i a l waster
Temperature Domestie and i n d u s t r i a l wastes
Color Domestic and i n d u s t r i a l wastea % Odor Decbnpostng aewage, i n d u e t r i a l wastes
Chemical
O i ~ d n i c : -
P r a t s i n o Domestic and comme~-of a 1 das tes
Carbohydrates DCmestic and commercial wastes
F a t s , o i l r , and greqse Domestic, commercial, and i n d a s t r i a l wastes
Surfactnnts Domestic and i n d u s t r i a l n a s t s e
Phenols I n d u s t r i a l vaa tes
p e s t i c i d m Agr iau l to ra l waster
Inorganicr
PI( I n d u s t r i a l wastes Chlorides Carr iage water, domestic wamtes, ground
water i n f i l t r a t i o n
Alka l in i ty Domestit wastes, ca r r iagu water, ground water i n f i l t r a t i o n
d i t rogen Domeatilr and e g r i e u l t u r a l v a s t e r
Phosvhorue Domestic and indnstr iml vaatea.
Table 5 : T y p i c a l s a n i t a r y chemical a n a l y s i s of sewage.
( Q u a l i t y of Domestic Wastes) ,
CONSTITUENTS
Salf dfi, Tot a 1
CVdlat i l e
Fixed
Suspended s o l i d s , T o t a l
V o l a t i l e
Fixed
Dissolved S o l i d s , T o t a l
V o l a t i l e
Fixed
S e t t l e a b l e s o l i d s
BOD (5 day 2 0 ' ~ ) ..-
Oxygzn consumed
Dissolved Oxygen
Nitrogen, t o t a l
0 r gan i c
Pree Ammonia
N i t r a t e (3NO ) 3
C h l o r i d e s
A l k a l i n i t y ( a s CaCO ) 3
F a t s
HZD I U M ( ~ g / l )
500
350
150
300
250
5 0 200
100
100
8
200
75 0
5 0 2 0
3 0 0 005
0.20
100
100
20
- Source: Bond and S t r a u b : (1974).
b
23.
Generally, biochemical oxygen demand (30D) is t h e rnlasure
of t he pol lut ional load of was t ewa te r on t h e oxygen r e s o u r c e s
of the receiving water w h i l e e s c h e r i c h i a c o l i f o r m (3. C o l i )
is used as an i n d i c a t i o n o f p o l l u t i o n a l l o a d i n g due t o
human i n t e s t i n a l t r a c t . ( P f a f f l i n a n d Z i e g l e r , 1976).
2.3.2. Y a s t e v a t e r Trea tment .
h sys tem of c e n t r a l c o l l e c t i o n , t r e a t m e n t and d i s p o s a l
i s a c h a r a c t e r i s t i c of u r b a n i s a t i o n where o n - s i t e t r e a t m e n t
of sewage is no l o n g e r p o s s i b l e because o f i n c r e a s i n g volume
o f wa te r u s e and s h o r t a g e o f l a n d f o r s u c h purposes . C e n t r a l
c o l l e c t i o n o f was t ewa te r n e c e s s i t a t e s c e n t r a l t r e a t m e n t
because decay ing o r g a n i c m a t t e r i s obnox ious and h a r b o u r s
d i s e a s e .,
The .?rimarg r e a s o n f o r t z g a t i n g any was t ewa te r is t h e need
f o r a v o i d i n g n u i s a n c e and dange rous c o n d i t i o n s i n t h e e n v i r o n -
ment. The re i s t h e need t o e n s u r e t h a t u n d e s i r a b l e c o n d i t i o n s
do n o t d e v e l o p i n t h e w a t e r body r e c e i v i n g t h e t r e a t e d was t e -
w a t e r e f f l u s n t ( P f a f f l i n and Z i e g l e r , 1976) . A c o n v e n t i o n a l
sewage t r e a t m e n t work c o n s i s t s of t h e f o l l o w i n g s t a g e s ( ' d h i t e ,
P r e l i m i n a r y Trea tment : s c r e e n s , g r i t s e t t l i n g t a n k s ,
s to rm t a n k s o r b a l a n c i n g t a n k s i n p a r a l l e l wi th
p r i e a r y s e d i m e n t a t i o n t a n k s , s torm-or ba l anc ing -
t a n k emptying pumps.
S ludge Trea tment : P h y s i c a l o r b i o l o g i c a l de-water ing
p r o c e s s e s . T r a n s p o r t o f s l u d g e from s i t e f o r
d i s p o s a l o r i n c i n e r a t i o n .
- Secondsry Trea tment : B i o l o g i c a l o r i n c i n e r a t i o n f i l t r a t i o n - . ' ' *
o r a c t i v a t e d s l u d g e , o c c a s i o n a l l y i n combinat ion.
I n a d d i t i o n t h e t r e a t n e n t works may i n c l u d e t e r t i a r y
t r e a t m e n t which c o n s i s t s of m i c r o - s t r a i n e r s o r sand f i l t e r s
L
t o improve t h e e f f l u e n t by removing f u r t h e r suspended o r g a n i c
- mat te r . - . - .
Metcalf and Eddy Inc , (1972) c l a s s i f i e d t h e s e s t a g e s
i n t o p h y s i c a l u n i t o p e r a t i o n s , chemical u n i t p r o c e s s e s and
b i o l o g i c a l u n i t p r o c e s s e s , The means of t r e ~ t m e n t i n which
t h e a p p l i c a t i o n of p h y s i c a l f o r c e s predominate a r e known a s
u n i t o p e r a t i o n s e,g, s c r e e n i n g , f l o c u l a t i o n , s e d i m e n t a t i o n ,
f l o a t a t i o n , vacuum f i l t r a t i o n , d ry ing e t c . While u n i t p r o c e s s e s
a r e means o f t r e a t m e n t i n which t h e removal of contaminants i s
brought about by a d d i t i o n of chemicals (chemical p r o c e s s e s )
o r by b i o l o g i c a l a c t i v i t y ( b i o l o g i c a l p rocesses ) such a s
chemical p r e c i p i t a t i o n , d i s i n f e c t i o n , b i o l o g i c a l o x i d a t i o n , e t c .
Treatment is s a i d t o be primary i f i t is without b i o l o g i c a l
b a s i s . I f t r e a t m e n t i n c l u d e s on ly s c r e e n i n g , sed imenta t ion ,
and c h l o r i n a t i o n of e f f l u e n t , t h e t r ea tmen t is c l a s s e d a s
pr imary ( P f a f f l i n and Z i e g l e r , 1976). Primary t r e a t m e n t is
b e t t e r t h a n no t r e a t m e n t a t a l l , Secondary t r ea tmen t i s g e n e r a l l y
, . accep ted as b i o l o g i c a l t r ea tmen t ( P f a f f l i n and Z i e g l e r , 1976).
-- I n b i o l o g i c a l t r e a t m e n t of wastewater , t h e o b j e c t i v e s a r e
t o c o a g u l a t e and remove n o n s e t t l e a b l e c o l l o i d a l s o l i d s and t o
s t a b i l i e e t h e o r g a n i c ma t t e r . For domestic wastewater t h e
o b j e c t i v e i s t o r e d u c e t h e o r g a n i c c o n t e n t ( Y e t c a l f and
Eddy Inc. 1972).
Secondary o r b i o l o g i c a l t r e a t m e n t is t h e most i m p o r t a n t
s t a g e of was t ewa te r t r e a t m e n t i n o r d e r t o achi.eve t h e pu rpose
o f v a s t e w a t e r t r e a t m e n t . The d i f f e r e n t methods f o r s econda ry
t r e a t m e n t i n c l u d e
( i ) a c t i v a t e d - s l u d g e
( i i ) t r i c k l i n g o r p e r c o l a t i n g f i l t e r s
and ( i i i ) l a g o o n s ( a e r o b i c , a n a e r o b i c and f a c u l t q t i v e ponds).
The a c t i v a t e d - s l u d g e p r o c e s s i s used a lmos t e x c l u s i v e l y i n 8
l a r ' g e c i t i e s . T r i c k l i n g f i l t e r s a r e o f t e n used i n s m a l l e r
c i t i e s and f o r h i g h - s t r e n g t h i n d u s t r i a l was t e s . Lagoons a r e
u sed f o r small c i t i e s where l a r g e l a n d a r e a i s a v a i l a ' 3 l e - ( N e t c a l f and Eddy Inc . 1972) . S t a b i l i z a t i o n pond method i s
a c o n d i t i o n where sewage is e f f e c t i v e l y t r e a t e d mere ly by
s t o r a g e i n r e l a t i v e l y s h a l l a w open ponds f o r p e r i o d s r a n g i n g
from a few d a y s t o a few weeks depending on c l i m a t i c c o n d i t i o n s
a n d t h e deghee of t r e a t m e n t d e s i r e d .
Whatever t h e method o f t r e a t m e n t , t r e a t m e n t works u s u a l l y
have a f i n a l p r o d u c t r e f e r r e d t o as e f f l u e n t , which u s u a l l y . . o f n e e d s t o be disposed{, U l t i m a t e d i s p o s a l o f was tewater e f f l u e n t -
- c a n be by d i l u t i o n i n t h e r e c i e v i n g body of wa te r ; by d i s c h a r g e
on l a n d ; o r i n some c a s e s sucn as i n d z s c r t ~ 1 2 s by
e v a p o r s t i o n i n t o t h e a tmosphere as wel l aa seepage i n t o t h e
- ground. Dispo;al by d i l u t i o n ( n f t e r p r e l i n i n a r y o r b i o l o g i c a l
\ '
t r e a t m e n t ) i n l a r g e r b o d i e s of w a t e r , such a s l a k e s , r i v e r s ,
e s t u a r i e s o r oceans i s by f a r t h e most common method ( ~ e t c a l f
and Eddy I n c , , 1972) . R e g a r d l e s s of t h e d i s p o s a l method t h e r e
a r e r e q u i r e d q u a l i t y s t a n d a r d s f o r t h e e f f l u e n t based on
d e s i r a b l e p h y s i c a l c h e m i c a l and b i o l o g i c a l c o n . ; t i t u e n t s ,
2 , i f a s t e w a t e r I r r i g a t i o n ,
d a s t e w a t e r i r r i g a t i o n i s t h e a p p l i c a t i o n o f was tewater and
- o r i t s e f f l u e n t on t h e l a n d f o r p u r p o s e s of c r o p p roduc t ion .
The r e c y c l i n g of human w a s t e s t o add n u t r i e n t s t o and improve
t h e p h y s i c a l q u a l i t y of t h e s o i l had been p r a c t i c e c i n a n c i e n t
t ims i n China and i n o t h e r a r e a s o f Xsia, The e a r l i e s t raw
sewage f a rms documented i n l i t e r a t u r e appea r t o be t h o s e o f
Banz lau , Germany which were i n o p e r a t i o n i n 1531 and t h o s e o f
. . Zdingurgh , S c o t l a n d which were a c t i v e a round 1050 (Shuva l
e t al, 1986) - T h e r e a f t e r t h e p r a c t i c e s p r e a d a c c r o s s Europe ,
- t h e Un i t ed S t a t e s and Mexico, A f t e r sometime t h e p r a c t i c e
d e c l i n e d f o r l a c k o f l a n d due t o t h e enchroachnent of urban
deve?oprnent. O t h e r f a c t o r s r e s p o n s i b l e f o r t h e d e c l i n e i n raw
, w a s t e w a t e r i r r i g a t i o n i n c l u d t h e problems of odour and t h e
c o n c e r n s abou t p u b l i c h e a l t h ( o a r t i c u l a r l y t h a t o f t h e
p o s s i b l e t r a n s m i s s i o n o f d i s e a s e s from v e g e t a b l e c r o p s
i r r i g a t e d w i t h raw sewage) a n d t h e d i s c o v e r y o f b i o l o g i c a l
p r o c e s s e s of t r e a t i n g was t ewa te r t h a t r e q u i r e d much l e s s l a n d
t h a n r a w sewage fa rms , : t h e
C u r r e n t l y , t h e m i s renewed i n t e r e s t fn L p r a c t i c e o f
was tewater i r r i g a t i o n i n many c o u n t r i e s o f t h e wor ld i n c l u d i n g
u n i t e d ~ i n g d o m , U.S.X., I s r a e l , I n d i a , F e d e r a l Repub l i c o f
Germany, Sou th A f r i c a , J apan , USSA', ' China , A u s t r a l i a as w e l l
as L a t i n American, Nor th A f r i c a n , Middle E a s t e r n a n d Sou th
3ast Asian c o u n t r i e s (Shuva l e t a l , 7986). No d e t a i l e d i n f o r -
mat ion is a v a i l a b l e on was t ewa te r r e u s e i n t h e l a r g e r p a r t o f
A f r i c a . There is t h e p o s s i b i l i t y t h a t as more c e n t r a l sewage
c o l l e c t i o n and t r e a t m e n t s y s t e m s a r e a d o p t e d i n A f r i c a , waste-
wa te r r e u s e i n a g r i c u l t u r e may s p r e a d i n t h e c o n t i n e n t .
The b e n e f i t s o f was t ewa te r i r r i g a t i o n a r e nunerous. It h a s
become an i m p o r t a n t s t r a t e g y f o r c o n s e r v i n g w a t e r r e s o u r c e s i n
a r i d and semi -a r id a r e a s of . t h e wor ld , Sven i n humid a r e a s
where t h e r e a r e r e g u l a r p e r i o d s o f d r o u g h t , t h e r e a r e d e f i n i t e
a d v a n t a g e s of was tewater i r r i g a t i o n , The f e r t i l i z e r v a l u e o f
- t h e n u t r i e n t s i n was tewater are a d d i t i o n a l economic i n c e n t i v e s ,
p a r t i c u l a r l y f o r d e v e l o p i n g c o u n t r i e s where t h e c o s t o f impor t ed
c h e n i c s l f e r t i l i z e r s makes i t d i f f i c u l t t o m a i n t a i n h i g h
l e v e l s of a g r i c u l t u r a l p r o d u c t i v i t y ( S h u v a l e t a l , 1986) .
Sewage i r r i g a t i o n c o u l d c o n t r i b u t e i n maximizing t h e e f f i c i e n t
t u s e of l i m i t e d l a n d r e s o u r c e s f o r t h e p r o d u c t i o n o f food and
+ f i b r e . Resources p r e s e n t i n was t ewa te r c a n be r e c o v e r e d when
u s e d on l a n d , and t he o t h e r w i s e d i s c h a r g e o f p o l l u t a n t s o f
wa te r b o d i e s and c o u r s e s e l l i m i n a t e d t h e r e b y improving t h e
w a t e r q u a l i t y o f such b o d i e s of w a t e r ( A r a r , 1987).
2.3.4. H e a l t h I n p l i c a t i o n s o f Wastewater I r r i g a t i o n .
Although was t ewa te r ( raw and t r e a t e d ) h a s been used as
i r r i g a t i o n w a t e r s o u r c e s i n c e a n c i e n t t i m e s , t h e n e g a t i v e
- h e a l t h i m p l i c a t i o n s were n o t d i s c o v e r e d u n t i l t h e t u r n of t h i s
c e n t u r y . Beginning i n 1912, numerous h e a l t h r i s k s a s s o c i a t e d
w i t h was t ewa te r i r r i g a t i o n have been r e v e a l e d . These r e v e l a t i o n s
a r e based on q u a n t i f i a b l e r e s e a r c h works , a few of which a r e
mentioned below as rev iewed by S h u v a l e t a l , (1986).
K h a l i l (1931) d i s c o v e r e d c a s e s o f a s c a r i a s i s and t r i c h u r i a s i s
among i n m a t e s of T a r a p r i s o n i n Egypt who consumed v e g e t a b l e s
from t h e sewage farm a t t a c h e d t o t h e p r i s o n . Baumhogger (1949)
' r e ~ o r t e d . t ha t a number of major e p i d e m i c s o f a s c a r i a s i s t o o k . .
p l a c e i n Dorrnstadt, Germany between I908 and 1909, d u r i n g 1921,
and b a t m e n 1945 and 1943. I n e a c h c a s e , t h e e p i d e x i c \vas
a s s o c i a t e d w i t h s e v e r e economic d i s l o c a t i o n s and food
s h o r t a g e s , The v e g e t a b l e s and s a l a d c r o p s grown on t h e -
Darmstadt sewage f a rms o b v i o u s l y made up a n impor t an t p a r t -.-
of t h e f o o d s u p p l y o f t h e p o p u l a t i o n of t h e c i t y d u r i n g
t h o s e p e r i o d s . A number o f s t u d i e s between 1923 and 1970
showed e v i d e n c e o f he lmin th t r a n s m i s s i o n by v e g e t a b l e s i r r i g a t e d
w i t h was te7vater i n Jerusa lem. 4 c h o l e r a o u t b r e a k i n J e r u s a l e m
i i i 7972 :;as found t o be a s s o c i a t e d w i t h t h e consumption o f
, , , a s t e~>~a te r i r r i g a t e d vege tab lz - . I n S a n t i a g o , C h i l e , i t w2s
d i s c o v e r e d b e t x e e n 1982 and 1984 th rough a nunber o f f i n d i n g s
t h a t typhod f e v e r was a s s o c i a t e d w i t h sewage i r r i g a t i o n . The
c s s e s o f typhod f e v e r were more s i g n i f i c a n t d u r i n g t 3 e d r y
e f f e c t s o f was t ewa te r i r r l , : s t i o n on peop le i n v o l v e d i n s e v a e e
f a rming as w e l l as c o n s u a e r s o f t h e p r o d u c t s of s u c h fa rms i n
U.S.A., I n d i a , Mexico, e t c (Shuval , e t a l , 1986).
I n many d e v e l o p i n g c o u n t r i e s where h e l m i n t h d i s e a s e s a r e
endemic, p r i o r i t y pa thogens a s s o c i a t e d w i t h d i s e a s e t r ansmi -
s s i o n 5y was tewa te r i r r i g a t i o n can be r anked i n d e c r e a s i n g
o r d e r of r i s k a s f o l l o i l s (Shuval e t a l , 1336) : - 1. High r i s k - h e h i n t h s
2. Lower r i s k - e n t e r i c h s c t e r i a acd pro tozoan
7. L e a s t r i s k - e n t e r i c v i r u s e s
Samsboye (1986) n o t e d t b a t wate r borne e n t e r i c d i s e a s e s
such as typhad f e v e r , b a c i l l a r y d y s e n t r y , a s i a t i c c h o l e r a
and i n f e c t i v e h e p a t i t i s can b e t r a c n d t o wa te r p o l l u t i o n of
faecal o r i g i n . Apar t from e n t e r i c d i s e a s e s , f i l a r i a s i s
and s c h i s t o s o r n i a s i s c a n be t r a c e d t o w a t e r p o l l u t i o n i n
some t r o p i c a l a r e a s . The d i s a d v a n t a g e s o f was t ewa te r
i r r i g a t i o n which a r e e s s e n t i a l l y h e a l t h based can be
sumnar ised as
(i) t ~ a n s m i s s i o n o f c o r n ~ u n i c a b l e d i s e a s e s t o
s u s c e p t i b l e sewage f a r m e r s and t h e g e n e r a l
p u b l i c who consume produce f r o a s u c h f a r m
a n d
(ii) p o l l u t i o n t o s u r f a c e w a t e r and groundwater
w i t h p a t h o g e n i c microorganisms and chemica l s
c a r r i s d by t h e wastewater . ,
2.3.5. P u b l i c H e a l t h based Requirements and Q u a l i t y
S t a n d a r d s o f Yas t ewa te r f o r I r r i g a t i o n .
G e n e r a l l y a c c e p t a b l e w a t e r q u a l i t y s t a n d a r d s f o r
i r r i g a t i o n have been c o n s i d e r e d e a r l i e r i n s e c t i o n 2.2.1.
I n a d d i t i o n , because o f t h e p e r c u l i a r i t i e s of was tewater , - .
o t h e r r e q u i r e m e n t s a r e n e c e s s a r y f o r c o n s i d e r a t i o n b e f o r e
any was t ewa te r can be used f o r i r r i g s t i o n . The p r a c t i c e o f
( d l M e t c a l f a n d Eddy Inc . (1972) s u g g e s t
t h a t p r e l i m i n a r i l y t r e a t e d sewage and/
o r u n d i s i n f e c t e d sewage e f f l u e n t c o u l d
b e a p p l i e d t o f i e l d c r o p s , such as c o t t o n ,
s u g a r b e e t s and v e g e t a b l e s grown f o r s e e d
p r o d u c t i o n .
( e ) The s t a t e o f C a l i f o r n i a and t h e !qorld S e a l t h
O r g a n i s a t i o n haye s u g g e s t e d t r e a t m e n t
r e q u i r e m e n t s and q u a l i t y s t a n d a r d s f o r
i r r i g a t i o n p u r p o s e s a s shown i n t a b l e s 6
a n d 7 r e s p e c t i v e l y (Shuva l , e t a l , (1986).
(f) The e f f l u e n t g u i d e l i n e s t h a t S h u v a l , e t a 1
(1986) recornxiended f o r u se i n u n r e s t r i c t e d
x a s t e x a t z r i r r i g a t i o a o f ali c r o 2 a i n c l u d i n g
v e g t t a t l s s a r l
( i ) Mot s o r e t 5 a n 1 v i a j l e c e z s t o d s
( h e l a i n t h ) egg ( a s c o r i s , t r i c h ~ r i s ,
hookxorn) p e r l i t e r .
California Stete Dcpar~ment of tiealth'standarda Tor thi: onfe . and direct use of reclai-d vaeteuvter for irr:gation and recreational i m p o u n ~ n t e
Description of minimum required vasteuater characteristics
-- Secondary coagulet eC Colilorm
Secondary filtered - b' ' M~N1100 ml and and median . Use of reclaimed uasteuarzr ~rimar~?' disinfected di sinfecred (daily ramp1 ing)
a. Effluent not containing more than 1.0 ml/liter/hr settlable solids. b. Effluent not containing more than 10 turbidity units.
I ! 1
Irrigation Fodder crops x No requirement Fiber crops x No requirement
Source: Af ter Ongerth and Jopl iug i n Shuva l et a1 (1986).
Seed crops x Produce eaten raw, surface irrigated x Produce eaten raw, spray irrigated
No requirement 2.2
x 2.2 Processed produce, surface irrigated x No requirement Processed produce, spray irrigated x 2 3
Landscapes, parks, etc. x ! 2 3 Creation of impoundments Lakes (aesthetic enjoyment or.? y) x 23
I Restricted recreational lc!:es x 2.2 . Nonrestricted recreational lakes x 2.2
Table 7
r '.Suggested t reehmnt processes t o m e t the given hea l th c r l t e r l e f o r res tare tar reuse
. I r r i g a t i o n Racraatlon -- uunic-ifal.p e U X
Crops not Crops eaten fo r d l r e c t ccoked; Crops
human f l s h eaten Ho Industrial Nan
e ~ s u m p t Ion c u l t u r e re. contact Contact reuse potable Potable
Primary t r ee fmn t e e e e.0 0.0 e.0 e e e e e e *em om.
Secondary treatment e.0 eoe ee. 0 . e.. em*
Second f i l t r a t i o n o r equlvalant w ison ing methods
Hi tri f i c a t i ~ t
-!hn k t r H i c a t i i m
Chemcal ' c la r l f l ca t i on
Ion exchange or other H e n s o f removing I m s . .
- ... ee. *.. e..
b a l t h c r i t r r i a :
A - Fr- f r a gross so l ids ; r l g n l t l c a n t r-vel o f paras l ta qys. B - As A, plus r l g n l f l c a n t r r r o v a l o f bacteria.. C - As A, p lus -0 r f f r c t l v r r w v a l o f baet r r la , p l u r saw ramoval o f v l ruras. 0 - Not Iwr than 100 c o l l f o c r org8nloc.s per 100 m1 I n IK) porcrn t of r w p l r r . E - No fecal c o l l f w m o r g a n l v s i n 100 ml. p l u r no v l r u r p a r t l c l o s i n 1OOO mI. p lus no t o x l c r f f u t s on man and other
dr ink ing r a t e r c r l t r r l a , . F - tb c h c l c a l s t ha t lead t o undesirable rosldues I n crops or f lsh.
G - M , c h m l c a l r t ha t lead t o lrrl t a t i o n o f mucous u r b r a n e r md rkln. . ..
I n w d e r to mt the glvan hea l t h c r l t r r l a , processes narke4 l l l .Ill k r s w n t l r l . I n eddl t ion, one w more processes rarked r l l l a lso k r r s o n t l a l , and f u r t h u p r o c r s u r marked 0 M y Sawtlmr k requlrod.
Free chlar ina a f t e r I hour.
Source: W30 in Shuval et a1 (1986) .
a n d ( i i ) a g e o m e t r i c mean n o t g r e a t e r t h a n -
1,000 f a e c a l c o l i f o r m b a c t e r i a p e r 100 m l , t h e y
In a d d i t i o n t o t h e above recommendation, ' L s u g g e s t
t h z t brhere was t ewa te r e f f l u e n t s z r e known t o c o n t a i n
pa thogens , t h e i r u s e f o r i r r i g a t i o n o f mzrke t v e g e t a b l e s
s h o u l d be p r o h i b i t e d .
a l s o s u g g e s t t h a t t h e f o l l o w i n g c r i t e r i a f o r t r e a t m e n t
of was t ewa te r f o r i r r i g a t i o n shou ld be met
( 1 ) Kwdnum r e ~ o v a l o f h e l m i n t h s
( 2 ) E f f e c t i v e r e d u c t i o n i n S a c t e r i a l and v i r a l
pz thogens
3 The p r o d u c t i o n o f n u i s a n c e - f r e e a n d odour - f r e e '
e f f l u e n t (i .e. BOD is e f f e c t i v e l y r educed) .
?e s t a b i l i z z t i o n pond cen c e e t t h e t h r e e c r i t e r i a . Well
d e s i g n e d and w e l l o p e r a t e d s e r i e s of s t a b i l i z z t i o n ponds
czn a c h i e v e z l z o s t t o t a l removal of h e l m i n t h s w h i l e 20 - day
s t 5 b i l i z a t i o n ~ o z d s c s n renove e lmos t a l l b a c t e r i a and v i r u s e s .
370
2.4 CRO? PRODUCTION W1Ti-I YASXYATER IRSIGATION.
2.4.1. E f f e c t s o n s o i l p r o p e r t i e s
Although sewage f a rming cou ld have a d v a n t a g e s due t o
r e c y c l i r g o f n u t r i e n t s and o r g s n i c n a t t e r t o t h e s o i l
( S a b e r , 19%) , w a s t e w a t e r as i r r i g a t i o n x a t e r , l i k e conven-
t i o n a l i r r i g a t i o n w a t e r f r o a e i t h e r s u r f a c e o r s u b s u r f a c e
s o u r c e s , may a f f e c t t h e s o i l p h y s i c a l , c h e n i c a l and b i o l c g i c a l
p r o p e r t i e s depend ing o n t h e c o n c e n t r a t i o n o f t h e c h a r a c t e r i s t i c
c o n s t i t u e n t s o f t h e i r r i g a t i o n was t eda te r . The e f f e c t s of
t o t a l s a l t 7 c o n c e n t r a t i o n 3 t k e r e l a t i v e c o n c e n t r a t i o n o f
s o i i u z i o r s t o o t h e r c a t i o n s and o t i e r s p e c i f i c i o n i c e f f e c t s
' . a s w e l l z s t u r h i d i t y i n x a a t e w z t e r SR s o i l p r o g e r t i e s a r e - - s i n i l a r t o t h e i r e f f e c t s when i n h i g h c o n c e n t r a t i o n s i n t h e
c o n v e n t i o n a l i r r i g a t i o n w a t e r a s d i s c u s s e d e a r l i e r i n s e c t i o n
2.2.2. Some o l t h e documented e f f e c t s o f was t ewa te r i r r i g a t i o n
o n s o i l are b r i e f l y g r e s e n t e d below:
In Gabel e l A s f a r sewage fa rm i n Ca i ro (Sabe r , 19861,
where t h e o n l y s o u r c e o f i r r i g a t i o n is d e c a n t e d sewage s i n c e
1925, seuage f a r m i n g t e n d e d t o b u i l d up m i c r o b i a l p o p u l a t i o n
a n d t o t a l b a c t e r i a c o u n t s as w e l l as t h e promot ion o f the
p r o l i f e r a t i o n -- o f p h y s i o l o g i c a l groups. T h i s p o p u l a t i o n h a s
a c c e l e r a t e d t h e o x i d a t i o n o f o r g a n i c m a t t e r t o a v a i l a b l e
n u t r i e n t s , It a l s o r e s u l t e d i n a h i g h i n c r e a s e i n n i t r o g e n ,
phosphorus , m i c r o - n u t r i e n t s , o r g a n i c c a r b o n and r a i s e d t h e
w a t e r h o l d i n g c a p a c i t y and exchangeab le c a t i o n s . The b a l a n c e
o f n u t r i e n t s i n s o i l appea red t o have been d i s t u r b e d as t h e
p9 s h i f t e d towards a c i d i t y . The f a e c a l 2. C o l i , which is
a n i n d i c a t o r o f t h e p re sence o f e n t e r i c pa thogens was found
i n a l l ae-.qaged s o i l s ,
I n as 8 - ~ % r sewage e f f l u s n t i r r i g a t i o n e x p e r i a e n t ,
3 e c n e t t s t a 1 (19731, e s t a ' d i s h o d t h a t t h e e f f l u e n t i n c r o 2 s e d
p?ms?horus, sodium, s 0 l u 3 l e s a l t s and p5 i n t h e s o i l ( a t 1;;
l e v e l o f s t a t i s t i c a l s i z n i f i c a n c e ) , P e r c i v a l (1984) obse rved -.-
t h a t t h z h i g h sodium c o n c e n t r a t i o 3 i n t 3 e K r 2 f t p u l p m i l l
e f f l u e n t u s e d as i r r i g a t i o n w a t e r s o u r c e i n t h e c e n t r a l ?Jorth
I s l a n d i n :law Zea land cou ld c a u s e s o i l d 'eflocul.at ' ion a f t e r
s e v e r a l years. C r o ~ e r e t a 1 (1984) e s t a 5 l i s h e d t h a t i r r i g a t i n g
w i t h s a l i n e was t ewa te r produced s u b s t a n t i a l i n c r e a s e s i n
exchangeab le s e d i u a and po ta s s ium, e x t r a c t a b l e phosphorus, pX
and t h e e l e c t r i c a l c o n d u c t i v i t y o f t h e s o i l and t h a t n i t r o g e n
remained l a r g e l y i n t h e o r g a n i c farm, Wastewater i r r i g a t i o n
c a n c a u s e o r i z c r e a s e heavy m e t a l b u i l d up i n t h e s o i l ,
39
S c h i r a d o e t a1 (1986) have shown t h a t u n t r e a t e d w a s t e w a t e r - i n c r e a s e d t h e l e v e l s o f e x t r a c t a b l e Cadaium, Coba l t , Copper ,
Manganese, n i c k e l and z i n c i n t h e c u l t i v a t e d l a y e r o f t h e
s o i l when compared t o t h e u n d i s t u r b e d lower l a y e r s . However
p o t e n t i a l heavy m e t a l h a z a r d i s l e s s i n h i g h exchange c a p a c i t y
s o i l s .
a '
r. 4.2. 3 f f e c t s o n Crops.
was t ewa te r i r r i g a t i o n of food and f i b r e c r o p s h a s been
known t o produce d i f f e r e n t r e s p o n s e s on d i f f e r e n t c r o p s .
" o r t e n e t a1 (1980) have e s t a b l i s h e d t h a t p e r e n i a l f a r a z e
g r a s s s s az? z a i z e y i e l C v e l l and e f f i c i e n t l y r eaovs l a r g e
amouafs o f n i t r o g e n from w a s t e v a t s r e f f l u e n t on w e l l manaqed
a c d p e r a e a b l e s o i l s . I n a g reen3ous3 e x p e r i z e n t x i t h d i f f a r e ~ t
t r e a t m e n t l e v e l s o f w a s t e w a t e r , 3aogSoye (19%) r e p o r t e d t h a t
sewaze e f f l u e n t t r e a t e d w i t h one h a l f t h e dosage o f f e r t i l i z e r
. r e q u i r e m e n t produced t h e h i g h e s t g r a i n y i e l d i n c o r n p r o d u c t i o n .
T e s t e r and P a r r (9982) r e p o r t e d t h a t was t ewa te r i r r i g a t i o n
- i n c r e a s e d y i i l d and q u a l i t y o f v e g e t a b l e s (cabbage , t oma toes
and caul i f lo : . , e r ) . I n a c o m p a r a t i v e s t u d y on c o t t o n i r r i g a t e d
w i t h w a s t e ~ ~ a t e r and p o r t a b l e w a t e r , Day e t a 1 (1981) n o t e d .. .
t h a t c o t t o n i r r i g a t e d w i t h a m i x t u r e o f was t ewa te r and p o r t a b l e
watlr hzd more v e g e t a t i v e growth a a d s t o o d h i g h e r t h a n
c o t t o n i r r i g a t e d w i t h o n l y p o r t a 5 l a water . It was a l s o
obse rved t h a t t h e y i e l d o f s e e d c o t t o n and l i n t c o t t o n
were b o t h h i g h e r i n t h e c a s e o f a mix tu re o f v s s t e w a t e r and
p o r t a b l e water . The L i n t c o t t o n q u s l i t y was hoxever t h e
sams f o r t h e two d i f f e r e n t t r e a t n o ~ t s . The above f i n d i c g s
x o u l d i n d i c a t e t h s t rnunic ina l w a s t e v a t e r can be a n e f f e c t i v e
i r r l g x f i o n !:12tor so2 r " as a e l l a s a sou rcd o f p l s c t n u t r i a n t s
i n co t5on p r o d u c t i o n i n Ar izoca , U . S . A . , where t h e s t u d y was
c a r r i o d o u t .
n i t r o g e n c o n t a n t a n d n s t s k e b j f o d d e r , maize and s p i n a c h
were i n c r e a s e d by a p p l y i n g i ~ c r e a s i - g n i t r o g e n r a t e s (0 - 153
kg/ha), f a r n y a r d manure o r t owr r e f u s e . S i m i l a r i n c r e a s e s
mix tu re o f sewage watsr and c a n a l m t z r c o q o s e d wi th c a n a l
w a t e r aLone.
- 2.5, CBOP SZLECTION FOR WSTZ-JATER IRRIGATION
.-
S h u v a l . e t a 1 (1986) has s u g g e s t e d t h r e e c o n s i d e r a t i o n s f o r
s a l e c t i n g c r a p s t o b e srot,qn undzr v a s t e w s t e r i r r i g a t i o n .
1. S u i t a b i l i t y o f c r o p t o t h e g e n e r a l agronomic
c o n d i t i o n s of t h e s i t e w i t h r e s p e c t t o c l i m a t e ,
s o i l t g p t s , a v a i l a S i l i t y of marke t , e t c . I n
ge9era1, any c r o p u s u a l l y grown by l o c a l f a r x r s
undor i r r i g s t i o n i n a given l o c s t i o n shou ld
s a t i s f y t h e c r i t e r i o n .
2. C o ~ s t r a i n t s on c r o p groxth .
T k s e c o n s t r a i n t s a r e due p r i n c i p a l l y t o t h e
s i l i n i t y o f e f f l u e n t which l i n i t s c r o p growth
aid c a u s e s t k e d e t e r i o r a t i o n of some o f t h e
p k j s i c a l a n d chemica l p r o 7 e r t i a s o f t h e s o i l
as w e l l a s t h e t o x i c e f f e c t o f s p e c i f i c i o n s
t o c e r t a i n c rops .
3. P u b l i c H e a l t h C o n s t r a i n t s .
These a r e c o n s t r a i n t s on c r o p u t i l i z a t i o n
o r m a r k e t i n g imposed by p u b l i c h e a l t h
c o n s i d e r a t i o n s o r r e g u l a t i o n s r e s u l t i n g f r o a
b o t h p a t h o g e n s and t o x i c chemica l c o n t e n t s o f
t h e w a s t e w a t e r t h a t can con tamina te t h e c rop .
The r a t i o n a l e o f c o n s i d e r i n g pa thogen c o n t a m i n a t i o n i n
s e l e c t i n g c r o p s t o 5 e i r r i g a t e d by was t ewa te r s t ems from t h e
obv ious - p ~ s s i b i l i t g o f t h e c o n t a m i n a t i o n o f t h e p l a n t p a r t s
d e s t i n e d f o r human consumption d i r e c t l y o r i n d i r e c t l y
w i t h i n a s h o r t p e r i o d a f t e r con tamina t ion and w i t h o u t %
-& f u r t h e r p r o c e s s i c g . The s u i t a b i l i t y o f c r o p s f o r was te-
w a t e r i r r i g a t i o n b a s e d on p o s s i b l e c o n t a a i n a t i o n 5y pa thogens
is g i ~ e n Selow i n d e s c e n d i c g o r d e r o f s u i t a b i l i t y :
( i ) Crops n o t grown f o r food such a s wood and
f i 5 r e c r o p s anong which c o t t o n i s by f a r t h e
n o s t i m p o r t a n t world ;#idem
( i i ) Ta l l -g rowing f ~ u i t and cnt t r e e s i r r i g a t e d
by s u r f a c e o r d r i p system o r low t r a j e c t o r y
s p r i n k l e r s .
( i i i ) B r a i n c r o p s and f r u i t c roFs f o r which
i r ~ i g a t i o n c o u l d be t e r ~ i n a t e d s e v e r 2 1
weeks b e f o r e h a r v e s t i n g and f r u i t s t h a t a r e
no rma l ly vashed and t r e 3 t e d b e f o r e consuap-
t i o n ( c i t r u s , o l i v e s , avocados e t c ) .
( i v ) Low-growing b u t e r e c t p l a n t s , grown i n t h e
r idge -and- fu r row s y s t e ~ and no t i r r i g a t e d by
s p r i n k l i n g . Such c r o p s i n c l u d e t a b l e g r a p e s
and t o m a t o e s grown o n t r e l l i s e s , swee t c o r n ,
peppe r , egg p l a n t , e t c .
(v) Crops t h a t a r e l e a s t s u i t a b l e f o r e f f l u e n t
i r r i g a t i o n a r e t h o s e w i t h s u p i n e growth h a b i t
s u c h a s Squash , Cucumbers, some tomato v a r i e t i e s ,
s t r a w b e r r i e s , p e a s , beans , r o o t c r o p s e a t e n
.. raid ( c a r r o t s , r a d d i s h ) a s w e l l a s a s p a r a g u s ,
p o t a t o e s , b e e t s , o n i o n s e t c .
The degree of t r e a t m e n t t o which t h e e f f l u e n t i s L
- s u b j e c t e d as w e l l a s t h e i r r i g a t i o n method used w i l l i n f l u e n c e
t h e s e v e r i t y o f t h e l i m i t a t i o n ,
The c h o i c e of a n m a n t h u s SPP. c r o p f o r t h e m i n e r a l a n a l y s i s
d e r i v e s from t h e f a c t t h a t i t i s t h e crop under waste-
water i r r i g a t i o n a t t h e s i t e under s tudy, Amaranthus i s a
v3ge tab le c r o o wi th nany s p e c i e s , soxe of ~dh ich a r e w i l d ,
Ar thur (1965). r e f e r s t o t h e v e g e t a b l e c r o p a s a l a r g e
group of quick-growing sp inach p l a n t s and i t i s connonly
r e f e r s d t o a s African a ~ i n a c i ,
Anaranthua i s an e a s i l y grown l e a f v e g e t a b l e v i t h a high
d i e t e t i c va lue . During t h e e a r l y r a i n s when t h e r e is s h o r t a g e . - C
of g reen v e g e t a b l e s , i t g i v e s an abuadance of g reen l e a f
( G r e e n s i l l , 7964). I n Niger i a , i t i s grown p - i n s i l y f o r i t s
g reen v e g e t a b l e supply.
Vege tab les a r e ve ry impor tant t o poor peop le i n many under-
developed c o u n t r i e s i n c l u d i n g N i g e r i a s i n c e t h e s e poor people
cannot a f f o r d enough meat o r f i s h and must depend on v e g e t a b l e s
- f o r much o f t h e f l a v o u r and t h e p r o t e i n r equ i rement i n t h e i r
food ( A r t h u r , 1965). Most v e g e t a b l e s need l a r g e amounts o f wa te r
and hence y a t e r supp ly i s o f t e n a l i m i t i n g f a c t o r i n v e g e t a b l e
farming. Consequent ly , i r r i g a t e d v e g e t a b l e f a rming is becoming
popular and common world wide,
HXT39I.iLS A';iD i1IE'THOrSS - - The g e n e r a l g u i d e l i n e s or r e q u i r s e c c c s f o r i r r i g d c l o n
% a t e ? azd t h e s g e c i Z i c r e q u i r e m o n t s f o r was tewater f o r
i r r i g a t i o n were c o n s i d e r e d i n t h e e x e c u t i o n of t h i s r e s e a r c h
work. These c o n s i d e r a t i o n s l e d t o t h e i d e n t i f i c a t i o n of t h e
f o l l o w i n g p a r a a e t e r s f o r e x m i n a t i o n .
S s v e n t e e n c n a r s c t e r i s t i c s o f was t ewa te r were c o n s i d e r e d
f o r e v s l u a t i o n i n ths l x b o r s t o r y ( t a 5 1 s 8 ) . S o i l a n a l y s i s
invol-:ed a c o n b i n a t i o n o f f i e l d and l a b o r a t o r y t e s t a f o r t h e
d e t e r m i n a t i o n of t h e ohgsical c h a r a c t e r i s t i c s ( f i e l d
t h e s o i l . C:hez ica l ~ a i g s i s o f t h e s o i l i n c l u d e d
l a b o r s t o r y e v a l u s t i o n o f 23, e l e c t r i c a l c o n d u c t i v i t y , c a t i o n
exchange c a p a c i t y , n i t r o g e n , phosphorus as !#ell as potassium,
sodium, ca l c ium a2d nagnessium. The v e g e t a b l e ( amaran thus SPP)
s a n p l e s were a n a l y s e d i n t h e l a b o r a t o r y f o r n i t r o g e n , phosphorus ,
. po t a s s ium, c a l c i u n , magnassium a a d s o d i u a c o n c e n t r a t i o n s .
The l a b o r a t o r y f a c i l i t i e s used f o r t h e l a b o r a t o r y work
of t h i s s t u d y - . i n c l u d e t h o s e of t h e f o l l o w i n g d e p a r t m e n t s / u n i t s
o f t h e U n i v e r s i t y of N i g e r i a , Nsukka campus:- C i v i l E n g i n e e r i n g
( p u b l i c ~ e a l t h ) , A g r i c u l t u r a l E n g i n e e r i n g , Geology, V e t e r i n a r y .
Table 8: Methods f o r t h e examinat ion o f wastewater
Refe rences
sample s .
American P u b l i c H e a l t h A s s o c i a t i o n e t a 1 (1971) f o r t e s t s 4 t o 11 and 13.
* * Vogel, A.1. (1972) - For t e s t 12
M E T H O D O L O G Y
Thermometer
E l e c t r i c a l C o n d u c t i v i t y me te r
pH meter
Gravimet r i c
S t a n d a r d Method
S t a n d a r d P l a t e count
Phenodisulphunic a c i d method
Stannous Chlo r ide
T u r b i d i m e t r i c method
Argentometr ic T i t r a t i o n
D o T A. T i t r a t i o n
E. D. To A. T i t r a t i o n
E- D - T. A - T i t r a t i o n
Flame Photometer
Flame Photometer
F l o a t a t i o n Method
F l o a t a t i o n Method
*** S h a p i r o and Branock, (1962)- For t e s t s 14 and 15
CHARACTZRISTIC
Temperature
E l e c t r i c a l Conduc- t i v i t y
PH T o t a l s o l i d s
BOD 5
B a c t e r i a l Densi ty
N i t r a t e
Phosphate
Su lpha t e
C h l o r i d e
Calc i um
Magnessium
Hardness
Potass ium
Sodium
Helminth egg count
P r o t o z o a
.-
L
8
8
- ** *
* * * 8 *
* * * * M i n i s t r y of A g r i c u l t u r e , Food and F i s h e r i e s London (1977). For t e s t 16 and 17,
S/NO. I
1.
2.
3 0
4 . 5. 6.
70 8 . 9.
10.
11.
12.
13.
14,
P a r a s i t o l o g y , Crop S c i e n c e a l d S o i l Sc i ence .
The e x p e r i n e n t a l area is t h e U n i ~ s r s i t y of S i g e r i a ,
wor!<s, l o c s t z d a t t h e S o u t h - a s s t e r n end o f Xsukka c a a p u s
soms 500 c z t r e s f r o a t h e j u i o r s t a f f q u a r t a r s , compr i s s a
z a t i o n ponds.
d s s c e v a t e r i r r i g s t i o n i z t h e area a round t h e t r a a t m z t
( 5 , 1 . The l a i i d undzr c a l t i v a t i o n s x t a a d s u? t o - -
tLs bun& of t h e ponds and c o v e r s l a n d a l o o g t h ? e f f l u e z t
c o u r s e s . The t o t a l a r e a under c u l t i v a t i o n i s e s t i m a t e d as 4 - 6
The sys tem o f i r r i g a t i o n a d o y t e d i s t h s c o r r u g a t i o n
v e r s i o n o f fu r row i r r i g a t i o n (F ig . 4). Wastewater is conveyed
- from t h e t r e a t m e n t works t o t h e c o r r u g a t i o n by g r a v i t y t h rough
temporary d i v e r s i o n s and by d i r e c t l i f t i n g o f was t ewa te r from
,he s o u r c e J i t h b u c k e t s . The main c r o p grown d u r i n g t h e s e a s o n
is amaranthus SPP. which is p o p u l a r l y known as ' g r e e n t . O t h e r
Wastewater Sampling p t ~
Soil Sampl ing P t s
V e g e t a b l e Sampling Pts
XO* are approximate Pts
lntormediate 11 1 effluent
S T A B 1 L I Z A T I O N ' = 3
P O N D 2
=I
=2
I FIG. 3'- SCHEMATIC DIAGRAM OF SAMPLING POINTS '
Fig 4: P r q a r e d c o r r u g z t i o n s rssdg f o r a n s r s n f h s s
seedlings.
v e g e t a j l e c r o p s gro ra are garden egg and f l u t e d punpkin
( t e l f a i r i a o c c i d e n t a l i s ) . Figures 5a a n d 5 b s h o w viesrs of
d i f f e r a n t s tages of a n a r a n t h u s p r o d u c t i o n a t t h e site d u r i r 3
t h e seak c u l t i v a t i o r p e r i o d . Oth2r food c r o p s s ~ c h as
c a s s x v a , yams, inel lon, etc. are c u l t i v a t e d in the r a i n y
s e a s o n at t h 2 sit; x i t h o - ~ t i r r i z a t i o n ( f i g ~ r ~ s 5 a m d b),
C1' A::? 2zsa m<;r st:?: is t . ; $ r z f ~ r e uzdar l c t i -72 c ~ o ? pro?uct!.o?
a l l y e a r rc~und.
F i g 5b:- L Xrjar,,,,ds c u l t i v a t i o n on t h e bund-of the ponds. O n t h e r i g h t i s Treatment Pond 1; on t h e l e f t i s T r e a t a e n t Pond 2. A t t h s f o r e g o m d i s a s e x e r d i s c h a r g i s g t h e i n t e r m e d i a t e e fT luen t from Fond 1 t o Poad 2.
F i g 6b.-
52
3.2. EVALUATIOH OF ;iASTEdATER CHARACTERISTICS
3.2.1. Sampling P o s i t i o n s and Frequsncy.
The sampl ing p o s i t i o n s f o r t h e wastewater examinat ion
a r e shown i n f i g u r e 3. The f i r s t sampl ing p o s i t i o n (I) is
a t t h e e n t r a n c e i n t o t h e f i r s t s t a b i l i z a t i o n pond where t h e
wastewater from t h e pr imary t r e a t m e n t ( : h e r e a f t e r r e f e r e d
t o a s t h e i n f l u e n t t o t h e s t a b i l i z a t i o n t r e a t m e n t sys tem)
i s r e c e i v e d i n t o , the f i r s t s t a b i l i z a t i o n pond (Pond 1 ) f o r
t h e secondary t r ea tmen t . The second sampl ing p o s i t i o n (11)
i s t h e e f f l u e n t from Pond I t o Pond 2 : h e r e a f t e r r e f e r e d t o
as t h e i n t e r m e d i a t e e f f l u e n t , wh i l e t h e t h i r d sampling
p o s i t i o n (111) r e p r e s e n t s t h e ou t f low from pond 2 which is
a l s o t h e f i n a l e f f l u e n t from t h e t r e a t m e n t ponds unto farm
l a n d s . The f o u r t h sampl ing p o s i t i o n (IV) is a t t h e o f f i c e o f
t h e s t a f f o f t h e t r e a t m e n t works and is t h e w a t e r ( t a p wa te r )
from t h e w a t e r d i s t r i b u t i o n system of t h e campus. The sampling
d a t e s and f requency a r e shown i n t a b l e 9
T A B U 9 sampl ing schedu le of t h e wastewater f o r examinat ion
DATS OF s AMPLING
7 - 1 2 - 88 18 - 1 - 89
b
27 - 2 - 8 9
16 - 3 - 89
TIME OF SAMPLING
9.00 - 10.o0 a.m.
9.00 - 10.00 a.m.
9.00 - 10.00 a.m.
9.00 - 10.00 a.m.
DATd OF COMMENCEMdNT
OF TESTS
7 - 12 - 88 18 - 1 - 89
2 7 - 2 - 89
1 6 - 3 - 89
DATE OF COMPLETION OF TZSTS
13 - I - 89
6 - 3 - 8 9
21 - 3 - 8 9
3.2.2. Laboratory Tests .
The l abo ra to ry t e s t s c a r r i e d out i n t h e s tudy a s we l l
as t h e procedures adopted f o r t h e t e s t s a r e i n d i c a t e d i n
t a b l e 8, A l l samples were preserved i n t h e r e f r i g e r a t o r
dur ing each examinat i o n period.
The temperature read ings f o r January were t aken a f t e r
t h e samples had s t ayed over n igh t i n t h e r e f r i g e r a t o r .
Consequently o n l y - t h e February and March 1989 va lues were
accep ted f o r ana ly s i s . The s tandard p l a t e count t e s t s were
0 on ly approximates because t h e i ncuba to r temperature was 37 C
i n s t e a d of 35 + 0.5'~ and t h e i n c u b a t o r s used d i d not f unc t i on
very well. The t o t a l s a l t concen t r a t i ons i n p a r t s per m i l l i o n
(ppm o r mg/l) were r e a d from f i g u r e I us ing t h e e l e c t r i c a l
c o n d u c t i v i t y values. The sodium adso rp t i on r a t i o (SAR) and
t h e exchangeable s o d i m percentage were determined from F i g 7, ++ us ing t h e concen t r a t i ons of Calcium and Magnessium (Ca + ~ g + + )
and t hose o f sodium.
Figure '7 . Noniogro~n for clctcr~iii~ii~ig, tlir SAR value of irri- gatio~i watcr micl for cstilnating the corrcspollclilig ESP valuc of a soil
. cquilibratcd with this watcr.
Source : S h a i n b e r g and O s t e r (1978).
55
3.3. EVXLUI\T~HG T 33 ZFFECT OF '/IABT"LUATER IRRIGATION
ON SOIL P30P32TIES.
Both f i e l d a n d l a b o r a t o r y t e s t s were c a r r i e d o u t t o
e v a l u a t e t h e e f f e c t o f was t ewa te r i r r i g a t i o n o n t h e s o i l . The
t e s t s were c a r r i e d o u t between A p r i l arid June I989 e x c e p t f o r
s i t e I on which t h e tests of t h e p h y s i c a l p r o p e r t i e s had been
c a r r i e d o u t e a r l i e r i n J m u a r y 1989.
Sampl ing po i r i t s were s e l e c t e d i n such a way t h a t t h e y
were f a i r l y d i s t r i b u t e d a c r o s s t h e a r e a under s t u d y . They were
e i g h t (8) s i t e s s e l e c t e d from ' the a r e a under was t ewa te r i r r i g a -
t i o n and two o t h e r s i t e s ( s i t e s 9 and 10) s e l e c t e d from a n a r e a
n o t s u b j e c t e d t o v a s t e u a t e r i r r i g a t i o n but w i t h i n t h e g e n e r a l
a r e a of t h e s t u d y . l h a s e two s i t e s were s e l e c t e d t o s e r v e as
c o n t r o l s t o t h e p o s s i b l e e f f e c t s was tewater i r r i g a t i o n h a s on
t h o s e p o r t i o n s o f t be a r e a s u b j e c t e d t o i r r i g a t i o n . T a b l e 10
g i v e s t h e d e t a i l s of t i e s i t e s s e l e c t e d f o r t h e s o i l t e s t s . While
t a b l e 1 1 g i v e s a f u l l d o c u m c n t a t l ~ ~ r ~ . "11 $>-: t o ~ ' , ~ c a r r i e d o u t
and t h e p rocedure adop ted f o r each.
Fd C 0 + 0 0 Y 0 rn'd + u +ti r n h ( D P
m I r-
57.
T a b l e 11: Methods used f o r t h e D e t e r m i n a t i o n of s o i l
p r o p e r t i e s .
PROPERTY
F i e l d C a p a c i t y
Pry Bulk 3 e n s i t y
P o r o s i t y
T e x t u r e
I n f i l t r a t i o n
E l e c t r i c a l c o n d u c t i v i t y
C a t i o n Exchange c a p a c i t y
N i t r o g e n
Phosphorus
Po ta s s ium
S o d i urn
Calc i um
Magnessium
S A R
E S P
NATURE OF PROPL3Tl
P h i s i c a l
p h y s i c a l
P h y s i c a l
P h y s i c a l
P h y s i c a l
Chemical
Chemical
Chemical
Chemical
Chemical
Chemical
Chemical
Chemical
Chemical
Chemical
Chemical
PIGTHODOLOGY
G r a v i m e t r i c method
G r a v i m e t r i c method
G r a v i m e t r i c
Bouyocus method
Double r i n g k n f i l t r o m e t e r
pH me te r
C o n d u c t i v i t y me te r
Ammonium s a t u r a t i o n n e t hod
K j e l d a h l method
Vanadomolybdate a e t h o d
Flame photometry
Flame photometry
Complexometric T i t r a t i o n
Complexometric T i t r a t i o n
From Nomogram
From Nomogram
3.4 EVALUATING THE EFFECT OF 'iIASTE'AXTZil IRRIGATION
ON TAYE IXIIGATED VZGiiTABLE ( MIA:IANTHUS SPP . ) The e v a l u a t i o n and a n a l y s i s o f t h e e f f e c t o f was te-
w a t e r on i r r i g a t e d v e g e t a b l e c o n s i d e r e d ma in ly t h e e f f e c t
of i r r i g a t i o n was t ewa te r on t h e m i n e r a l compos i t i on o f
a m a r a n t h u s SPP.
3.4.7. Sampl ing
Twelve samples o f amaranthus SPP v e g e t a b l e were o b t a i n e d
f o r t h e a n a l y s i s . Nine samples were o b t a i n e d from p r o d u c t s
grown under was t ewa te r t r e a t m e n t i n t h e g e n e r a l a r e a o f t h e
t r e a t m e n t works ( f i g 3 ) , t h r e e from e a c h of t h e t h r e e l o c a t i o n s
%..
o f w a s t e w a t e r 2onds e v a l u a t e d . The r ema in ing t h r e e samples
were o b t a i n e d from v e g e t a b l e grown w i t h p o t a b l e w a t e r , farm
y a r d manure and/or f e r t i l i z e r a t l o c a t i o n s d i f f e r e n t from t h e
s t u d y a r e a b u t w i t h i n t h e U n i v e r s i t y town o f Nsukka. I n
a d d i t i o n , v e g e t a b l e ( amaran thus SPP) was grown i n t h e s t u d y
- a r e a and i r r i g a t e d w i t h p o t a b l e t a p w a t e r ( f i g 8 ) . A l l s amples
were o b t a i n e d from t h e f i r s t c u t t i n g of t h e l u s c i o u s s t a n d s
(March - May 1989). Vege tab le s amples were o b t a i n e d w i t h i n a
p e r i o d of one veek and t h e sampl ing t i m e was u s u a l l y between
7.00 a.m. and 8.00 a.m.
b
Fig 8: Amaranthus SPP grown in the study area
and irrigated with only potable tap
water.
3.4.2. The Mineral A n a l y s i s of
The samples ob ta ined were I
s ampl ing a t a tempera ture o f 60
60 . Vegetable Samples.
d r i e d i n t h e oven a f t e r each
+ 4 ' ~ f o r a p e r i o d of - approx imate ly twelve hours . T h e r e a f t e r t h e samples were
m i l l e d i n a hammer m i l l i n t o f i n e powdery form. Tab le 12
g i v e s t h e e l ements a n a l y s e d and t h e procedure adopted f o r
each.
Tab le 12:- Methods used f o r t h e m i n e r a l a n a l y s i s o f
amaranthus SPP. samples.
Element
Ni t rogen
Phosphorus
Potassium
C a l c i urn
Nagnessium
Methodology -- - - - - - -
K j e l d a h l Method
Phosphorus - Molybdate Method
Flame Photometry
3. D. T. A . Method
E o D. T. A . Method
Sodium I Flame Photometry sir.
CHXPTZR FOUR
R X S U L T S .
CHARACTZ3ISTICS.
The t e m p e r a t u r e , p 3 and t o t a l s o l i d s of t h e was t ewa te r
sampled a t t h r e e l o c a t i o n s a l o n g t h e t r e a t m e n t gonds and o f
t h e t a p wa te r f o r t h e s t u d y e a r i o d ( ~ e c e r n b e r 1988 t o March
1989) are shown i n t a b l e 13. Tempera tu re was lowes t i n
J anua ry b u t d i d n o t v a r y be tween l e b r u a r y and March. The
i n f l u e n t t e m p e r a t u r e was c o n s i s t e n t l y ( t h o u g h s l i g h t l y ) h i g h e r
t h a n t h o s e a t t h e o t h e r two l o c a t i o n s . The was tewater pH was
c o n s i s t e n t l y h i g h e r t h a n t h a t o f t h e t a p water . There were
d i f f e r e n c e s i n p a among t h e l o c a t i o n s f o r e a c h month b u t t h e r e
was no c o n s i s t e n t p a t t e r n . T o t a l s o l i d s was h i g h e s t i n t h e
i n f l u e n t i n a l l t h e months , w h i l e t h e i n t e r m e d i a t e and f i n a l
e f f l u e n t s d i d n o t d i f f e r much e x c e p t i n Feb rua ry when t h e f i n a l
e f f l u e n t was v e r y h igh . Compared w i t h t h e t a p w a t e r , average
of t o t a l s o l i d s of w a s t e w a t e r . was f o u r t e e n f o l d s h i g h e r ,
Four b i o l o g i c a l c h a r a c t e r i s t i c s o f was t ewa te r a r e shown
i n t a b l e 14. The BOD 5
months,. Though on t h e
e f f l u e n t and t h e f i n a l
w a s h i g h s s t i n t h e i n f l u e n t f o r a l l t h e
a v e r a g e , t h e BOD . f o r t h e i n t e r m e d i a t e 5
e f f l u e n t were t h e same, t h e y v a r i e d on
t ' t ' 0 0 n o P w n CT t'. I-. C 0 P P
I-. I 0
a
0 n : 2 m m 1 CI a FI I-. m e e m I-. P pl . CT
m
m -2 b P c
2 rt -. S w CT r . 0 P
1-1
111:
1
''1 F..
e w I-
m b -2
P c e * -.
I-. 0
P
n I::
monthly b a s i s wi thou t any c o n s i s t e n t t r e n d . The BOD f o r 5
t a p water f o r ~ e c e m b b r was much h i g h e r than f o r January and
Narch which were very smal l . On t h e whole, t h e BOD f o r 5 . t h e wastewater was h i g h e r t h a n f o r t h e t a p water . The
s t a n d a r d p l a t e count f o r t h e wastewater was h i g h e r t h a n t h a t
f o r t h e t a p wa te r throughout t h e per iod . There was however
no c o n s i s t e n t t r e n d w i t h t h e wastewater l o c a t i o n s . Helminth
e g g s were c o n s i s t e n t l y p r e s e n t on ly i n t h e i n f l u e n t waste-
w a t e r i n c o n c e n t r a t i o n s r a n g i n g from 20 p e r l i t r e t o 60 p e r
l i t r e . P ro tozoa o o c y s t s were found i n two out o f t h e f o u r
sampl ing times i n c o n c e n t r a t i o n s of 20 p e r l i t r e each t ime
and only i n t h e i n f l u e n t .
The chemical c h a r a c t e r i s t i c s of t h e samples w i t h i n t h e
p e r i o d a r e shown i n t a b l e 15. The e l e c t r i c a l c o n d u c t i v i t y
(LC.), from which t h e t o t a l s a l t was determined, was con-
s i s t e n t l y h i g h e r i n t h e wastewater t h a n i n t h e t a p wa te r and
c o n s i s t e n t l y h i g h e s t i n t h e i n f l u e n t wastewater . The Z.C. f o r
- t h e i n t e r m e d i a t e and f i n a l e f f l u e n t s were s i m i l a r excep t f o r
February when t h e f i n a l e f f l u e n t w a s much higher . On t h e
a v e r a g e , t h e n i t r a t e c o n t e n t of t a p wa te r was h i g h e r t h a n t h o s e
of t h e wastewater . J anuary and February n i t r a t e c o n c e n t r a t i o n s
2
2 2 0 UI 05 c . ~ ; ? $ ~ p p \ . n p p g g .l \,a .F - m . F - m ca N 0 V l o 0 Vl O N - 03 &- &-
W
0 N O 3 - Oa L - C U l O N W O O E m
W W a 2 m 2 A 2 V l N V l N N w a p p V l U ) . . . . . 0 I I$ o m o c - O ' > b L ; I w u l o o o w w W . I O O \ i l " m
o f t a p water were t h e same. The n i t r a ~ e concencrabAun
of t h e i n f l u e n t was c o n s i s t e n t l y h i g h e r t h a n t h o s e o f t h e
- i n t e r m e d i a t e and f i n a l e f f l u e n t . Phospha te c o n c e n t r a t i o n
\
i n t h e w a s t e w a t e r was c o n s i s t e n t l y h i g h e r t h a n t h a t o f
t h e t a p wa te r . Phosphate was h i g h e s t i n t h e i n f l u e n t
-- -- s l igh t ly_-decreas ing- f rom- i - n f l u e n t - - t o -- -- f i n a l -- --- - . e f f l u e n t --- .- f o r t h e -. -
months o f J a n u a r y , F e b r u a r y a n d Narch. The r e v e r s e was t h e
c a s e f o r December 1988, C h l o r i d e c o n c e n t r a t i o n w a s h i g h e s t
among t h e a n i o n s i n t h e was t ewa te r and i t s v a l u e s were
a p p r o x i m a t e l y similar f o r t h e t h r e e l o c a t i o n s . The c h l o r i d e
i n t h e was t ewa te r was on t h e a v e r a g e 27 t i m e s t h a t i n t h e
t a p wa te r . The c a t i o n s - ca l c ium, Magnessium, Sodium and
Po ta s s ium - were c o n s i s t e n t l y very low i n t h e t a p wa te r , They
were however h i g h i n t h e w a s t e w a t e r w i t h t h e i n f l u e n t
h a v i n g t h e h i g h e s t . Magnessium d e c r e a s e d from t h e i n f l u e n t t o w h i l e
t h e f i n a l e f f l u e n t L ~ a l c i u m , Sodium a n d Potass ium d i d n o t show
any c o n s i s t e n t t r e n d . Among t h e c a t i o n s i n t h e was t ewa te r t h e
- c o n c e n t r a t i o n o f sodium was h i g h e s t . The SAR and ESP were
c o n s i s t e n t l y low wi thou t any t r e n d among t h e l o c a t i o n s .
T a b l e 16 shows a compara t ive a n a l y s i s o f t h e cha rac -
t e r i s t i c s o f t h e was t ewa te r o f t h e t h r e e l o c a t i o n s i n t h e
t r e a t m e n t works w i t h t h o s e f o r t a p wa te r . Except f o r t h e L
n i t r a t e c o n c e n t r a t i o n , a l l t h e o t h e r c h a r a c t e r i s t i c s were
h i g h e r f o r a l l t h e l e v e l s o f was t ewa te r t h a n t h o s e f o r t a p
wa te r .
T a b l e 17 is t h e Duncan New ~ u l t i p l e Range T e s t a n a l y s i s
o f t h e c h a r a c t e r i s t i c s by l o c a t i o n s . Except f o r n i t r a t e a n d
s u l p h a t e , t h e r e were s i g n i f i c a n t d i f f e r e n c e s between t h e
means o f t h e t a p water and a t l e a s t one o f t h e l o c a t i o n s of
,, t h e was t ewa te r f o r a l l t h e o t h e r c h a r a c t e r i s t i c s . The BOD 5
a n d t h e E.C. f o r t h e i n f l u e n t were s t a t i s t i c a l l y s i g n i f i c a n t l y
d i f f e r e n t from t h o s e o f t h e i n t e r m e d i a t e e f f l u e n t and t h e
f i n a l e f f l u e n t . The i n f l u e n t t o t a l s o l i d s was s i g n i f i c a n t l y
d i f f e r e n t from t h a t o f t h e i n t e r m e d i a t e e f f l u e n t bu t was t h e
same w i t h t h a t f o r t h e f i n a l e f f l u e n t . The pH, phospha te , . c h l o r i d e , h a r d n e s s , t h e c a t i o n s and t h e SAR had means t h a t
were s t a t i s t i c a l l y t h e same f o r t h e t h r e e l o c a t i o n s o f t h e
was t ewa te r .
T a b l e 16: Comparat ive A n a l y s i s of the Means of Wastewater
c h a r a c t e r i s t i c s w i t h Tap Ya te r .
C h a r a c t e r i s t i c
Tempera ture
pH
T o t a l s o l i d s -- -
S t a n d a r d p l a t e coun t
Helminth e g g
P r o t o z o a c y s t
E l e c t r i c a l Conduct i v l - t y
T o t a l s a l t
N i t r a t e
Phospha te
S u l p h a t e
C h l o r i d e
Calcium
Magnessiurn
Hardness
Po ta s s ium
S o d i urn
S A R
Zornparative v a l u e s o f * L o c a t i o n s k
I -- - -
1.025
1.479
17 653 . -
12.549
594.49 Very l a r g e
Very l a r g e
25.271
14
0 553 12.301
27 5F3 29.896
2 725 4.070
2.788
21.109
25.110
6.000
h t a p us
TT
0 995 7.422
I I -281 . -..- -
7 707
562.99 0
0
19.271 11
0 375 6.781
74.767
26.434
2.339
3.423
3.151 18.609
20.83
5.600
*The v a l u e s f o r l o c a t i o n s I , TT and ,IT? were d i v i d e d by t h e
c o r r e s p o n d i n g v a l u e s f o r l o c a t i o n I V ( t a p w a t e r ) t o g e t t h e
v a l u e s i n t h e t a b l e . b
68.
FsS
le
17: Y
ean
se
pa
ratio
n o
f la
ste
wa
ter a
nd
Tap
wa
ter
ch
ab
ac
teris
tics
by lo
ca
tion
__
__
---
-- by
the
D
un
can's
New
M
ultip
le ra
ns
e
tes
t at 5%
lev
el,
.
m
Hean
s
' T.S. (33%
o f th
e
Ele
me
nts.
- Z
.yo4
so2; PO';
c1-
ca ~g
Ha
rdn
ess
Lo
ca
tion
I
- In
flue
nt
I I -
- In
term
ed
iate
efflu
en
t
I11 -
- F
ina
l efflu
en
t
Tap
:d
ater
:lean
s fo
llow
ed
by
the
same
lette
r a
re
sta
tistic
ally
the
same,
wh
ile
ne
an
s follo
we
d b
y
diffe
ren
t lette
rs
are
sta
tistic
ally
sig
nific
an
tly
a
diffs
nt a
t 5% le
ve
l of
pro
ba
bility
as
by
th
e DNHRT.
4.2. SOIL PBOP~RTIZS
4.2.7, The P h y s i c a l : P r o p e r t i e s
- Table 18 shows t h e p h y s i c a l
of t h e S o i l .
p r o p e r t i e s of t h e s o i l from
t h e v a r i o u s sample l o c a t i o n s .
The mean of t h e f i e l d c a p a c i t y (F.C.) f o r IOcrn, 20cm,
and 40cm d e p t h s f o r t h e i r r i g a t e d a r e a were co r respond ing ly
h i g h e r t h a n t h o s e from t h e c e n t r a l a r e a , The h i g h e s t va lue
f o r t h e IOcm d e p t h of 16.22% from s i t e 5 was approx imate ly
t w i c e t h e lowes t of 7.89% from s i t e I . A t t h e 2Ocm and 40cm
d e p t h s t h e h i g h e s t F.C. were bo th from s i t e 7 whi le t h e lowest
were b o t h from s i t e 3. For t h e c o n t r o l l o c a t i o n s s i t e 9 had
= c o n s i s t e n t l y h i g h e r v a l u e s of F.C. t h a n s i t e 10 f o r t h e t h r e e
dep ths . The b u l k d e n s i t i e s a t 0 - I5cm and 20 - 35cm d e p t s
were lower f o r t h e i r r i g a t e d a r e a t h a n t h e c o n t r o l a rea . The
p o r o s i t i e s were h i g h e r a t b o t h d e p t h s (0 - I5cm and 20 - 35 cm)
f o r t h e i r r i g a t e d a r e a ,
The t . e x t u r a 1 c l a s s i f i c a t i o n of t h e a r e a i s predominant ly
- s a n d y , r a n g i n g from s a n d , loamy sand , sandy loam t o sandy c l a y
loam. The c o n s t a n t i n f i l t r a t i o n r a t e r e s u l t s d i d not show any
c o n s i s t e n t t r e n d . The i n f i l t r a t i o n r a t e s were i n g e n e r a l very
h i g h and o n l y r e s u l t s of t e s t s t h a t l a s t e d up t o 90 minutes o r
4,2.2, Chemical P r o p e r t i e s o f t h e s o i l .
Tab le 19 g i v e s t h e chemical a n a l y s i s of t h e s o i l proper-
t i e s examined. A 1 1 t h e chemical p r o p e r t i e s examined, except
t h e pH, were h i g h e r i n t h e i r r i g a t e d a r e a t h a n t h e non-
i r r i g a t e d c o n t r o l a r e a . Tab le 20 g i v e s t h e mean and t h e
s t a n d a r d d e v i a t i o n of t h e s o i l chemical p r o p e r t i e s as i n f l u e n c e d - - . - - - - -
by sewage t r ea tmen t . The pe rcen tage d i f f e r e n c e s i n d i c a t e
i n c r e a s e s of t h e s e p r o p e r t i e s i n t h e i r r i g a t e d a r e a compared
t o t h e c o n t r o l but a d j a c e n t a rea . Of t h e s i x e l ements d e t e r -
mined, t h e c o n c e n t r a t i o n o f n i t r o g e n was t h e h i g h e s t , i n both
t h e i r r i g a t e d and i n t h e c o n t r o l b u t a d j a c e n t a r e a whi le t o t a l
phosphorus was t h e lowes t .
From t h e chemical a n a l y s i s , l o c a t i o n 5 had t h e h i g h e s t
c o n c e n t r a t i o n o f most o f t h e e l ements examined fo l lowed by
l o c a t i o n 4. The lowes t i n t h e i r r i g a t e d a r e a was from l o c a t i o n
12.37 113-21
12.56 j 12-98
10.20 1?.88
1,420 1.238
1.518 1.371
46.4 51.0
42.7 48.3
84-16 84.0
;.o 0
15.82 16.0
sandy S
an
dy
loam loam
4.545
43.6 41.8 84.56 1.44
14.00 toady
sand
90
1 7-59
45.5 42.0
-88.72 0
11.28
mam
y sa
nd
Percen
t1
Percen
ts
Percen
tc
Overall
Con
stant
ramre
~y
:
cn
em
ca
L p
ro-p
erries or soils
rrom ergnt
rae
atlo
ns
irr
iga
ted
w
ith Y
asteu
ater
comp
ared w
ith
-,
two
so
il samples from
ra
ad
jacen
t rrer.
Prop
erty -3-11
t Locations
wit1
1 I
sd area
5 3.20
150 8.750
105-996 0.2648 5.344
6
0.717b 0.925 o.3E3 7 .O
. .
PE
4.60 E
lbtttita
l Co
nd
uctiv
ity
Um
hos#cm
85
Ca
tion
Exch
ange
Capacity
Meg/100g 3.775
W
3';.1;75 ,
It
0.058~
1 . p r o p e r t i e s as i n f l u e n c e d by sewage t r ea tmen t .
P r o p e r t y
N i t r o g e n
Phosphorus
Potass ium
Sodium
Calcium
Magnessium
S A R
ESP.
Mean
3.76
188
5.065
51.615
0.1138
0.2620
0.4947
1.011
0.363
0.825
0.186
C o n t r o l 1 S t d
e v i a t i o n
0
0.41
0.2298
0.3528
0
0.0152
0.01 70
0.0615
3.0792
0
0
' pe rcen tage Di f fe rence
L - 4.8 251
92
122
135
45
6
110
205
-17.5
-38
+Percen tage d i f f e r e n c e i n t h e means i s c a l c u l a t e d by
t h e equa t ion .
%D = (Treatment Mean - C o n t r o l mean) x 100% . . . . (2) C o n t r o l Mean
P o s i t i v e v a l u e s of p e r c e n t a g e d i f f e r e n c e show i n c r e a s e d
e f f e c f w h i l e n e ~ a t i v e v a l u e s show decreased e f f e c t due
t o wastewater t r e a t m e n t .
73 . . 4*3* TI-B HINZRAL CONPOSITION OF LEXVZS OF MARANTHUS SPP.
- The p e r f o r m m c e of . t h e v e g e t a b l e grown i n t h e s t u d y
- a r e a and i r r i g a t e d w i t h p o t a b l e t a p w a t e r was ve ry poor .
More t h a n h a l f of t h e p l a n t s , e i t h e r d i d n o t s u r v i v e t h e
t r a n s p l a n t i n g o r d i d n o t deve lop more t h a n t h e i r s e e d l i n g
s i z e s . Most of t i e s u r v i v o r s s t a r t e d f l o w e r i n g and f r u i t i n g
much e a r l i e r t h a n e x p e c t e d w i t h o u t t h e f u l l development o f
t h e v e g e t a b l e l e a v e s , Consequen t ly no d e t a i l e d m i n e r a l
a n a l y s i s o f t h e p r o d u c t s from t h i s c r o p p i n g was c a r r i e d o u t
b e c a u s e o f t h e growth performance.
The m i n e r a l compos i t i on o f t h e s a n p l e s a r e shown i n
t a b l e 21. Xnaranchus SPP l e a v e s sampled from o u t s i d e t h e s t u d y
a r e a have h i g h e r c o n c e n t r a t i o n s o f t h e p r o p e r t i e s examined
t h a n a l l t h e s a r n ~ l e s o b t a i n e d from t h e was t ewa te r i r r i g a t e d
a r e a , Except f o r ca l c ium t h a t showed s i g n i f i c a n t l y h i g h e r
c o n c e n t r a t i o n f o r two o f t h e t h r e e samples i r r i g a t e d w i t h t h e
i n f l u e n t , most of t h e c o n c e n t r a t i o n s o f t h e o t h e r ? r o p e r t i e s
' were s i m i l a r f o r a l l t h e samples from t h e i r r i g a t e d a r e a ,
T a b l e 22 g i v s s t h e Duncan New 1 4 u l t i p l e Range T e s t a n a l y s i s
f o r t h e m i n e r a l compos i t i on o f amaran thus SPP v e g e t a b l e by
l o c a t i o n w h i l e t a j l e 23 b r i n g s o u t t h e e l e m e n t s t h a t a r e
7.4.
T a b l e 21: M i n e r a l C o n t e n t s o f l e a v e s of amaranthus S p e c i e s
TREATMEN
I
I n f l u e n t
I1 - I n t e r - m e d i a t e
e f f l u e n t
I I1 - F i n a l
e f f l u e n t
grown on s o i l s i r r i g a t e d w i t h t h e was tewater
( i n f l u e n t ; . i n t e r m e d i a t e e f f l u e n t and f i n a l
e f f l u e n t ) and w i t h o r d i n a r y water .
SAMPUS
1
2
3
Nean
1
2
3
Mean
1
2
3
Ne a n
1
2
3 Mean
~~- -
PHOS- PHOaUS
%
0 75 0.63
0.55
0.643
0.66
0.63
0 59
0.627
0.59
0 53 0.31
0 . 477 0.70 0.63
0.70
0 677
POTASSIUM
%
1.5 1.4
1.4.
1 e43
1.2
1.6
1.2
1.33
1.5
1-3 1.5
1.43
1.8 2.4
1.4
2.03
MAGNESS I U P
L 0.24 0.18
0.15
0.19
0.24
0.30
0.30
0.28
0.58
0.18
0.15
0.303
0.30
0.37 0.46
0 . 377
75
T a j l e 22: The e f f e c t o f t r e a t m e n t
Yastewater l o c a t i o n and t a p wa te r on t h e
chemica l composi t ion of Amaranthus l e a v e s ,
Mean s e p a r a t i o n i n columns by Duncan's new
m u l t i p l e range t e s t 5% l e v e l ,
I = I n f l u e n t , ,I1 = I n t e r m e d i a t e e f f l u e n t , T I 1 . . = F i n a l e f f l u e n t
-- IS = Tap-water - - ( p l u s p o u l t r y manure and/or f e r t i l i z e r ) z -L
- -- . - Means f o l l o w e d by t h e sane a l p h a b e t a r e s t a t i s t i c a l l y the - -
s a n e , whi l e means fo l lowed by d i f f e r e n t a l p h a b e t s a r e
s t a t i s t i c a l l y d i f f e r e n t a t 5% l e v e l of p r o b a b i l i t y as by
Table 23: Elements and s t a t i s t i c a l D i f f e r e n c e s between t a p
wa te r and t h e d i f f e r e n t l o c a t i o n s ( t r e a t m e n t s ) o f wastewater .
Treatment
I n f l u e n t
I n t e r m e d i a t e -I-- ar I l u e n t
F i n a l E f f l u e n t
Minera l s t h a t show s t a t i s t i c a l d i f f e r e n c e between t h e treatmenk means.
N , Ca i N, P , C a , Na
s t a t i s t i c a l l y d i f f e r e n t between t h e t a p water t reatment
and d i f f . e ren t t r e a t h e n t s of t h e wastewater. The means of
a l l t h e p r o p e r t i e s examined a r e s t a t i ' s t i c a l l y t h e same
b f o r t h e t h r e e l o c a t i o n s of wastewater used.
CHAPTER FIVE
D I S C U ~ S I O N ,
5.1 T83 QUALITY OF TI33 UNIVERSITY OF NIGZRIA,
NSL'KKX 'XXSTX';JATE3 FOR IRRIGATION.
Zxzep t f o r n i t r a t e , t h e d i f f e r e n t c o n s t i t u e n t s o f t h e
w a s t e w a t e r f r o n t h e U n i v e r s i t y of N i g e r i a , J sukka t r e a t m e n t
ponds were found t o be c o n s i s t e n t l y h i g h e r t h a n t h o s e o f t h e
t a p w a t a r ( t a b l e A3 - 15) . The m u l t i p l e r a n g e t e s t ( t a b l e 17 )
shows t h a t f o r most o f t h e c h a r a c t e r i s t i c s , t h e r e is s i g n i f i c a n t
d i f f e r e x e be tween t h e was t ewa te r l o c a t i o n s and t h e t a p w a t e r
examined. 3 a s e d on t h e above r e s u l t s and t h e f a c t t h a t t h e
t a p watlr a n a l y s e d i n t h i s s t u d y is c o n s i d e r e d p o t a b l e , t h e
was t ewafe r f r o n t h e U n i v e r s i t y t r e a t m e n t ponds is no t p o t a b l e . -F
The n o s t i m p o r t a n t c r i t e r i a f o r e v a l u a t i n g q u a l i t y o f
w a t e r f 3 r . i r r i g a t i o n p u r p o s e s a r e t h e s a l i n i t y and s o d i c i t y
l e v e l s . The a n a l y s i s o f t h e t h r e e l o c a t i o n s o f was tewater
i n t h i s s t u d y showed h i g h s a l i n i t y l e v e l a t t h e t h r e e l o c a -
t i o n s , T h i s means t h a t t h e p r o b a b i l i t y f o r s a l i n i t y h a z a r d
* is h igh . The u s e of t h i s s o u r c e of w a s t e w a t e r f o r i r r i g a t i o n
i s l i k e l y t o i n c r e a s e t h e sa l t c o n c e n t r a t i o n i n t h e s o i l
s o l u t i o n . T h i s i s s u p p o r t e d by t h e r e s u l t o f t h e chemica l
a n a l y s i s of t h e s o i l s i n t h e i r r i g a t e d a r e a ( t a b l e 1 9 ) which
shoved c o n s i s t e n t l y h i g h e r s a l t c o n c e n t r a t i o n a t t h e l o c a t i o n s
b
78
of was t ewa te r t r e a t m e n t even though t h e s a l t c o n c e n t r a t i o n s
a r e n o t a t t o x i c l e v e l . S a l i n i t y problem from i r r i g a t i o n
w a t e r be s i g n i f i c a n t i n a r e a s where t h e w a t e r t a b l e i s h i g h ,
o r where t h e s o i l i s a l r e a d y s a l i n e o r i n a r i d r e g i o n s . I n
t h e s t u d y a r e a as i n most p a r t s o f Msukka, t h e w a t e r t a b l e
is very low ( o v e r 1CO x e t r e s below t h e ground) ; t h e low pH
a n d e l e c t r i c a l c o n d u c t i v i t y v a l u e s o f t h e s o i l o f t h e s t u d y
area show t h a t t h e s o i l s a r e n o t s a l i n e ; and t h e a r e a under
s t u d y i s n e i t h e r a r i d n o r s emi -a r id . Consequent ly , a l t h o u g h
t h e i n f l u e n t / e f f l u e n t s o f t h e U n i v e r s i t y o f N i g e r i a , Nsukka
was t ewa te r t r e a t n e n t x o r k s nay be c o n s i d e r e d s a l i n e , t h e
e f f e c t i v e s a l i n i t y hazard due t o i ts use a s i r r i g a t i o n w a t e r
i s low.
The s o d i c i t g l e v e l s i n d i c a t e d by t h e sodium a d s o r p t i o n
r a t i o (SAR) were low f o r t h e t h r e e l o c a t i o n s of t h e was tewater .
The p r o b a b i l i t y of sodium h a z a r d as a r e s u l t o f t h e a p p l i c a t i o n
of t h i s was t ewa te r f o r i r r i g a t i o n is t h e r e f o r e low. The s o i l
t e x t u r e i n t h e s t u d y a r e a h a s a low c o n t e n t o f c l a y which
- makes t h e d e f l o c u l a t i o n e f f e c t o f sodium c o n c e n t r a t i o n
n e g l i ' g i b l e . The combined e f f e c t of s a l i n i t y h a z a r d and.
sodium h a z a r d as r e f l e c t e d i n f i g . 2 shows t h a t t h e Un ive r s i t y
of N i g e r i a , 8 sukka wastev.gater i s s u i t a b l e f o r i r r i g a t i o n b
p u r p o s e s i n t h i s r e g a r d .
The most i m o o r t a n t c r i t e r i a f o r t h e d e t e r m i n a t i o n of
t h e s u i t a b i l i t y o f w a s t e x a t e r f o r i r r i g a t i o n depend on t h e
c o m p o s i t i o n o f v i a b l e p a t h c g e n i c o rgan i sms i n t h e was t ewa te r
( S h u v a l e t a1 1986). Thzse o rgan i sms i n c l u d e b a c t e r i a ,
v i r u s e s , h e l m i n t h s and 2,-otazoa v h i c h a r e o f t e n r e s p o n s i b l e
f o r t h e t r a n s m i s s i o n of d i f f e r e n t d i s e a s e s on ep idemic s c a l e .
S h u v a l e t a1 (1986) recommended t h a t was tewater f o r un res -
t r i c t e d i r r i g a t i o n s h o u l d not c o n t a i n more t h a n 'one v i a b l e - .
h e l m i n t h e g g ( a s c a r i s , t r i c h u r i s , hookworm) p e r l i t r e and n o t
g r e a t e r t h a n 1,000 f a e c a l Co l i fo rm (3 ~ o l i ) b a c t e r i a p e r
'100~1. The i n f l u e n t was t eVd3 te r c o n s i s t e n t l y had a high
c o n c e n t r a t i o n o f he l rn in th e z g s r a n g i n g from 20 t o 60 p e r l i t r e
d u r i n g t h e s t u d y p e r i o d . T h i s i s 2000 - 6000% above a l l o w a b l e
naxinun. E x c r e t e d h e l n i n t h s a c c o r d i ~ g t o Shuva l e t a1 (1986)
c a n be c l a s s i f i e d i n t o s e v e n t e e n t y p e s a l l o f which have man
as one o r t h e o n l y h o s t . D i s e a s e s c a u s e d by h e l m i n t h s a r e as
many as t h e i r t y 2 e s and i n c l u d e a s c a r i a s i s , hookworm,
t r i c h u r i a s i s , s t r o n g y l o i d i a s i s , e t c , These d i s e a s e s o c c u r
i n . t h e f o r m s of mechan ica l o b s t r u c t i o n -by round worms, anaemia
by hookworms, abdominal p a i z s , damage t o l i v e r o r l u n g s , e t c
( S h u v a l e t a l , 1986) . Of a i l t h e pa thogens , h e l m i n t h s
b
c o n s t i t u t e t h e h i g h e s t r i s k i n w a s t e w a t e r i r r i g a t i o n , The
i n f l u e n t was t ewa te r i n t o pond I i s t h e r e f o r e a dangerous
s o u r c e of w a t e r f o r i r r i g a t i o n . The p r o b a b i l i t y of t h i s
i n f l u e n t t r s n s a i t t i n g h e l m i n t h d i s e a s e s when used as i r r i g a -
t i o n w a t e r i s ve ry high. C u r r e n t l y , t h e p r a c t i c e i n t h e
s t u d y a r e a is t o l i f t was t ewa te r f o r i r r i g a t i o n from t h e
n e a r e s t p a r t of t h e ponds ( i n c l u d i n g t h i s i n f l u e z t ) t o t h e
i r r i g a t e d l a n d .
The i n t e r ~ e d i a t e e f f l u e n t and t h e f i n a l e f f l u e n t were
o n t h e o t h e r hand c o n s i s t e n t l y f r e e o f any h e l m i n t h egg f o r
t h e p e r i o d o f t h e s tudy . T h i s means t h a t t h e t r e a t m e n t i n
Pond 1 a c c o n p i i s h e d comple te removal of n e l m i n t h eggs. Hence
t h e u s e of t h e was t ewa te r i n Pond 2 and t h e f i n a l e f f l u e n t
f o r i r r i g a t i o n is s a f e w h i l e t h e was t ewa te r i n Pond I i s no t
s u i t a b l e a s i r r i g a t i o n w a t e r i n t h i s r ega rd . I f t h e was tewater
i n pond 1 must be used as i r r i g a t i o n w a t e r it s h o u l d be used
f o r i r r i g a t i n g s u c h c r o p s as c o t t o n a n d v e g e t a b l e s f o r s e e d
p r o d u c t i o n ( H e t c a l f and Eddy I n c , 1972).
Al though t h e p r o t o z o a c o n c e n t r a t i o n i s n o t a c r i t e r i o n
i n S h u v a l l s recommendations ( ~ h u v a l e t a1 1986) f o r was t ewa te r
f o r f r r b g s t i o n , t h e a n a l y s i s c a r r i e d o u t i n t h i s s t u d y showed
20 c y s t s p e r l i t r e a t t h e i n f l u e n t l o c a t i o n ( I ) . P a t h o g e n i c
p r o t o z o a s r e kaovn t o cause s i c k n e s s e s l i k e d i a r r h o e a d y s e n t r y ,
l i v e r a b s c e s s a n d m a l a b s o r p t i o n ( S h u v a l e t a l , 1986) . T h i s
f i n d i n g t h e r e f o r e a l s o s u p p r t s t h e f a c t t h a t t h e i n f l u e n t
was t ewa te r is u n f i t f o r i r r i g a t i o n . The s t a n d a r d b a c t e r i o l o -
g i c a l c r i t e r i o n f o r d e c i d i n g t h e s u i t a b i l i t y of was tewater
f o r i r r i g a t i o n is t h e d e t e m i n a t i o n o f t h e f e a c a l c a l i f o r m ,
E s c h e r i c h i a Coliforrn ( 3 C o l i ) and n o t t h e s t a n d a r d p l a t e count
de t e rmined i n t h i s a n a l y s i s . Bovever , Agus iobi (1976)was of
t h e o p i n i o n t h a t t h e b a c t e r i a removal was n o t good enough f o r
t h e w a s t e w a t e r t o 5 e * x e d f o r i r r i g a t i o n . Shuva l e t sl (1986)
a l s o s u g g e s t e d t h a t where w a s t e x a t e r e f f l u e n t s a r e known t o
c o n t a i n p a t h o g e n s , t h e i r us? f o r i r r i g a t i o n o f marke t v e g e t a b l e s - - - . -
s h o u l d be p r o h i b i t e d . Pa thogen ic j a c t e r i a a r e known t o
t r a n s m i t d i s e a s e s s u c h as d i a r r h o e a typhod f e v e r , c h o l e r a ,
b a c i l l a r y d y s e n t r y , e t c ( ~ h . l v a l e t a l , 1986). A p r o p e r examina-
t i o n f o r t h e f e a c a l c o l i f o r z ( E . C o l i ) b a c t e r i a a t t h e t h r e e
was t ewa te r l o c a t i o n s x i l -1 be n e c e s s a r y t o d e t e r m i n e t h e e x t e n t
o f c o n t a m i n a t i o n and t h u s s g e c i f j t h e e x t e n t o f 2 o s s i b l e u s e
o f t h e w a s t e u a t e r f o r i r r i g a t i o n g e n e r a l l y and f o r i r r i g a t i o n
- o f v e g e t a b l e s i n p a r t i c u l a r ,
Values o f b i o c h e m i c a l oxygen demand (BOD ) r a n g i n g from 5
100mg/l t o 300 mg/l a r e c o n s i d e r e d a c c e p t a b l e (Agus iob i , 1976).
Consequen t ly t h e 3OD v a l u e s ( a v e r a g e o f 191 mg/l) o f t h e 5
i n t e r a e d i a t e and f i n a l e f f l u e n t s a r e a c c e ~ t a b l e , n u i s a n c e - f r e e a n d o d o u r - f r e e and s u i t a b l e as i r r i g a t i o n wa te r . The
f a c t t h a t t h e r e i s s i g n i f i c a n t d i f f e r e n c e i n BOD between t h e
i n f l u e n t a n d t h e e f f l u e n t s show t h a t t h e deg ree o f p o l l u t i o n
i s s i g n i f i c a n t l y reduced .
The c h m i c a l a n a l y s i s of t h e t h r e e l o c a t i o n s o f was te-
[ i a t e r showed s i g n i f i c a n t d i f f e r e n c e s be tween t h e i r means on
t h e one hand and t h a t o f t h e o r d i n a r y w a t e r on t h e o t h e r
e x c e p t f o r n i t r a t e and s u l p h a t e ( T a b l e 17) . However t h e r e
were no s i g n i f i c a n t d i f f e r e n c e s o f t h e means of t h e t h r e e
d i f f e r e n t l o c a t i o n s of ? fas t enrtter fop- ;no&-of-f he- chsaica1.- - -
p r o p z r t i e s . :{~st of t h e s e c h e n i c a l s - o r l n i n e r a l s a r e e s s e n t i a l
m a c r o - n u t r i e n t s f o r c rop p r o d u c t i o n . The u t i l i z a t i o n of t h i s
was t ewa te r f o r i r r i s a t i o n w i l l t h e r e f o r e s u p p l y needed n u t r i e n t s
f o r c r o p p r o d u c t i o n ;dhich i s one of t h e a d v a n t a g e s o f was te- - - .
w a t e r i r r i g a t i o n ( ~ h u v a l e t a l , 1986). The was t ewa te r i n
Pond 2 c a n t h e r e f o r e be s e e n as a r e s e r v o i r of b o t h w a t e r
and n u t r i e n t s f o r c r o p p roduc t ion . The s i g n i f i c a n c e o f t h i s
i s o b v i o u s i n 4 i g e r i a v h e r e c h e m i c a l f e r t i l i z e r s a r e expens ive
and somet imes n o t a v a i l a b l e . It lwould appea r t h a t t h i s was te-
w a t e r n u t r i e n t s o u r c e h a s c o n t r i b u t e d immensely t o c r o p produc-
t i o n Yn t h e s t u d y a rea . During t h e i r r i g a t i o n s e a s o n ( d r y
s e a s o n ) t h e s e n u t r i e n t s a r e d i r e c t l y s u p p l i e d from t h e a p p l i e d
8 3.
w a s t e w a t e r , During t h e r a i n - f e d , c r o p a i n g s e a s o n ( r a i n y
s e a s o n ) , t h e r e s i d u a l e f f e c t of t h e d ry s e a s o n a g p l i c a t i o n
s u s t a i n s t h e c r o p s grown i n t h e a r e a w i t h o u t t h e need t o
a p p l y chemica l f e r t i l i z e r . Although t h e was t ewa te r i n pond 1
a l s o c o n t a i n s t h e s e n u t r i e n t s ; o t h e r c r i t e r i a a l r z a d g -
d i s c u s s e d p r o h i b i t i t s use a s i r r i g a t i o u w a t e r .
5.2, T S ElTIECTS OF JASTEJATER IRRIGATIOiI ON SOIL
PROPZRTIZS.
5.2.1. E f f e c t on t h e p h y s i c a l p r o p e r t i e s of t h e s o i l .
F i e l d Capac i ty . - --.-- -.
Three dep ths : IOcm, 20cm and 40cn were c o n s i d e r e d f o r
t h e d e t e r m i n a t i o n of t h e f i e l d c a p a c i t y . The r e s u l t s shoved P
t h a t t h e mean v a l u e s f o r t h e r e s p e c t i v e d e p t h s were h i g h e r
f o r t h e a r e a under was t ewa te r i r r i g a t i o n t h a n t h e l o c a t i o n s
o u t s i d e t h e i r r i g a t e d a r e a . These % d i f f e r e n c e s were 48.89%,
15.8% and 8.72% h i g h e r f o r t h e d i f f e r e n t c o r r e s p o n d i n g d e p t h s
r e s p e c t i v e l y . T h i s c a n be due t o t h e t e x t u r a l compos i t i on of
t h e s o i l . The r e s u l t s of t h e t e x t u r a l compos i t i on of i n d i v i d u a l
l o c a t i o n s r e v e a l t h a t l o c a t i o n s 4 and 5 which have a b o u t t h e
h i g h e s t compos i t i on o f c l a y p a r t i c l e s and t h e l o w e s t . sand
p a r t i c l e s have abou t t h e h i g h e s t w a t e r h o l d i n g c a p a c i t i e s .
Xowever l o c a t i o n 7 v h i c h had v e r y c l o s e l j h i g h w.at?r h o l d i n ?
c a p a c i t i e s a t t h e t h r e e d e p t h s h a s h i g h e r s a n d and lower
c l a y c o n t e n t s t h a n l o c a t i o n s 4 and 5. T h e r e f o r e a n o t h e r
p o s s i b l e r e a s o n f o r t he above d i f f e r e n c e s may be as a r e s u l t - . - . - -- - - - -
o f t h e m o d i f i c a t i o n o f t h e s o i l s t r u c t u r e caused by t h e
o r g a n i c m a t t e r c o n t e n t o f t h e % a s t e w a t e r . T h i s p o s s i b l e
r e a s o n becomes more t e n a b l e when i t i s n o t i c e d t h a t t h e
d i f f e r e n c e s i n f i e l d c a p a c i t y a r e l a r g e s t a t t h e t o p s o i l
l a y e r (0 - 10cm) w:?ere t h s o r g s c i c m a t t e r c o n t e n t of thk-rase*-
w a t e r is .' i n c o b p e r a t e d more. .- -- -4- -. " . - - - ,
Pro longed use o f was t ewa te r as i r r i g a t i o n w . ~ t a r on t h e
n a t u r a l l y p redominan t ly sandy s o i l o f t h e s t u d y s i t e h a s
a p p a r e n t l y i n c r e a s e d t h e f i e l d c a p a c i t y of t h e s o i l and
c o n s e q u e n t l y con f i rmed S a b e r ' s (1986) f i n d i n g i n C a i r o , Esyg t . . -
- -
P o r o s i t y and Bulk Dens i ty .
The p o r o s i t y which was de te rmined at two d e p t h s ( 0 - l 5 c a
a n d 20 - 35cm, , t a b l e 18) showed t h a t t h e i r r i g a t e d a r e a had
s l i g h t l y h i g h e r p o r o s i t i e s a t bo th d e p t h s t h a n t h e n o n - i r r i g a t e d
a r e a . T h i s d i f f e r e n c e can be a t t r i b u t e d t o t h e textural corn-
p o s i t i o n of t h e s o i l and/or t h e m o d i f i c a t i o n o f s o i l s t r u c t u r e
r e s u l t i n g from was tewa te r i r r i g a t i o n .
The b u l k d e n s i t y of t h e s o i l was r e d u c e d under was te-
w a t e r t r e a t n s n t ss s h o u l d 5e e x p e c t e d because o f t h e i n c r e a s e d
p o r o s i t y . The d i f f e r e n c e s i n b u l k d e n s i t i e s were l a r g e r a t
t h e t o p s o i l l a y e r s t r e n g t h e n i n g t h e s u g g e s t i o n t h a t t h e
e f f e c t of w a s t s w a t e r i r r i g a t i o n on t h e p h y s i c a l p r o p e r t i e s
of t h e s o i l is more pronounced a t t h e t o p s o i l l a y e r .
I n f i l t r a t i o n C a p a c i t y
The c o n s t a n t i n f i l t r a t i o n r a t e t e s t s showed v e r y h i g h
i n f i l t r a t i o n r a t e s e x p e c t e d on p redominan t ly s andy s o i l s , The
i n f i l t r a t i o n tests. had some u n f o r s e e n p r a c t i c a l p roblems t h a t
t h e y c o u l d c o t a l l be s u b j e c t e d t o t h e same t ime d u r a t i o n ,
So t h e i n f l c ~ c c e of t h e was t ewa te r a p p l i c a t i o n on t h e i n f g l -
t r a t i o n o f ,-iatsr i n t o t h e s o i l canno t be f u l l y a s c e r t a i n e d .
However t h e i i g h e r nean i n f i l t r a t i o n r a t e s o b t a i n e d under
was t ewa te r t r e s t ~ e n t ( t a b l e 1 8 ) i s i n keep ing w i t h i t s (was t e -
w a t e r ) a l r e a i y p r e s e n t e d e f f e c t on t h e s o i l p o r o s i t y .
5.2.2. E f f e c t s of ' J a s t e v a t e r I r r i g a t i o n on t h e chemica l
P r o p e r t i e s o f t h e s o i l .
The c h e z i - a l p r o p e r t i e s o f t h e s o i l s amples from t h a
w a s t e w s t e r i r r i g a t e d a r e a showed h i g h e r c o n c e n t r a t i o n s of most
e l e m e n t s t h a n rhose from t h e n o n - i r r i g a t e d a r e a (Tab le 19) .
T a b l e 2 0 sno-:#s t h e mean and s t a n d a r d d e v i a t i o n o f t h e s o i l h
c h e a i c a l p r o p a r t i e s as i n f l u e n c e d by Vas t ewa te r aonl;crL;u~i.
The pli v a l u e o f t h e t r e a t e d ales was abou t 5% lower
t h a n t h a t f o r t h e cnnt-n l 1:=:'2n?s- T h i s a g r e e s w i t h
S a b e r ' s f i n d i n g ( 1 9 8 6 ) , t h a t t h e a p p l i c a t i o ~ o f sewage
e f f l u e n t ( o f human w a s t e s ) on s o i l s t ended t o l ower t h e pH.
A l t k ~ . i z h L e i i e r e t a 1 (1984) r e p o r t e d t h a t i r r i g a t i n g w i t h
w a s t e w a t e r produced s u b s t a n t i a l i n c r e a s e i n pH, t h e was te-
wa te r t h e y a n a l y s e d was a l k a l i n e .
The p e r c e n t a g e d i f f e r e n c e approach used t o compare t h e
c h e m i c a l c o n c e n t r a t i o n s -of t h e s o i l ( t a b l e 20) shows t h a t t h e
e l e c t r i c a l c o n d u c t i v i t y a n d magnessium c o n t e n t s were h i g h e r
i n t h e was t ewa te r i r r i g a t e d a r e a by ove r 200%; n i t r o g e n ,
phosphorus and .calcium .by 92%; po ta s s ium by 45% and sodium
by 6%. ,These d i f f e r e n c e s a r e s u b s t a n t i a l enough t o c o n v e r t
a n i n f e r t i l e s o i l i n t o a f e r t i l e s o i l . T h i s a g r e e s w i t h
3 a b e r t s . ( 1 9 8 6 ) o b s e r v a t i o n t h a t was tewater a p p l i c a t i o n t o s o i l
can r e c y c l e n u t r i e a t s t o t h e s o i l .
P r c l o n g e d x a s t e w a t e r i r r i g a t i o n i n t h e s t u d y a r e a
i n f l u e n c e d t h e c h e n i c a l p r o p e r t i e s by c r e a t i n g ( i n c r e a s e d
d i f f e r e n c e s i n t h e compos i t i on of t h e d i f f e r e n t e l e m e n t s o f
t h e i r r i g a t e d a r e a o v e r t h e n o n - i r r i g a t e d a r e a . These
d i f f e r e n c e s a r e hoxever n o t v e r y uni form a c c r o s s t h e i r r i g a t e d
87.
area as shown i n t a b l e s 19 and 20. Such v a r i a t i o n s c o u l d
be due t o t h e d i f f e r e n t s o u r c e s o f was t ewa te r a p p l i e d t o
e a c h s p e c i f i c l o c a t i o n (Tab le 10). L o c a t i o n 5 which h a s
t h e h i g h e s t c o n c e n t r a t i o n f o r a o s t o f t h e e l e m e n t s h a s two
s o u r c e s (pond 1 and d i r e c t a p p l i c a t i o n o f raw was tewater
s i p h o n e d from s e p t i c t a n k s ) . L o c a t i o n 4 which h a s t h e n e x t
h i g h e s t c o n c e n t r a t i o n s is t h e n e a r e s t l o c a t i o n t o t h e i n f l u e n t
and i r r i g a t e d from pond 1. L o c a t i o n 1 which had t h e l e a s t
c o n c e n t r a t i o n s f o r most of t h e e l e m e n t s is n o t as c o n s t a n t l y
i r r i g a t e d w i t h w a s t e w a t e r ss t h e o t h e r l o c a t i o n s . Hence t h e
q u a n t i t y , q u a l i t y c o n c e n t r a t i o n o f was t ewa te r used and t h e
f r e q u e n c y of a p p l i c a t i o n a r e s i g n i f i c a n t i n t h e o v e r a l l e f f e c t
of was t ewa te r on t h e c h e m i c a l p r o p e r t i e s o f t h e s o i l .
Based on t h e f o r g o i n g , d i s c u s s i o n on t h e q u a l i t y of t h e
U n i v e r s i t y of N i g e r i a , Xsukka wa.s tewater a n d i t s e f f e c t on
t h e s o i l p r o p e r t i e s , t h e i n t e r m e d i a t e and f i n a l e f f l u e n t s
o f t h e U n i v e r s i t y of N i g e r i a , Nsukka t r e a t m e n t works is n o t
o n l y a s u i t a b l e i r r i g a t i o n wa te r s o u r c e b u t i t s a p p l i c a t i o n
* a l s o enhances. t h e f e r t i l i t y and t h e most p o s i t i v e c h a r a c t e r i s t i c s
o f t h e s o i l f o r c r o p p r o d u c t i o n ,
5.3 EFFECT OF ;/ASTE;dbT52 ON SOi4E 03 !HZ WIiiERhL
CONSTITUENTS OF AMARANTHUS SPP. VEGJTXBLL LdBVL3.
T a b l e 21 shows t h a t t h e n i n e samples from t h e i r r i g a t e d
a r e a have m i n e r a l c o n t e n t s o f similar c o n c e n t r a t i o n s . T h e i r
c o n c e n t r a t i o n s were however l o v e r t h a n t h o s e of t h e t h r e e
samples i r r i g a t e d w i t h p o t a b l e t a p wa te r ( a n d t r e a t e d v i t h
farm y a r d manure and/or f e r t i l i z e r ) at l o c a t i o n s o u t s i d e t h e
s t u d y a r e a . T h i s may be due t o e i t h e r a r e l a t i v e l y h i g h
s a l i n i t y o f s o i l s o l u t i o n caused by t h e was t ewa te r and which
c a n d e p r e s s n u t r i e n t up take by t h e p l a n t o r t h e i n h e r e n t l ower
n u t r i e n t c o n t e n t i n t h e w a s t e w a t e r i r r i g a t e d s o i l compared t o
t h e s o i l o u t s i d e t h e s t u d y a r e a . The l a t t e r is l i k e l y t o be
t h e c a s e because e a r l i e r a n a l y s i s h a s i n d i c a t e d t h a t t h e
i r r i g a t e d a r e a canno t be c o n s i d e r e d s a l i n e .
The g rowth per formance o f amaranthus gram i n t h e s t u d y
a r e a w i t h o u t t h e use of w a s t e w a t e r shows t h a t t h e s o i l o f t h e
s t u d y a r e a is n a t u r a l l y d e v o i d o f e s s e n t i a l p l a n t n u t r i e n t s and
canno t s u p p o r t p r o f i t a b l e v e g e t a b l e fa rming . T a b l e 24 which
g i v e s t h e compar ison of t h e s e e s s e n t i a l n u t r i e n t s of t h e
i r r i g a t e d a r e a and the n o n - i r r i g a t e d a r e a c o n f i r m s t h i s .
Table 24. Concentra t ions of t h e E s s e n t i a l Macro-nutrients
of t h e wastewater i r r i g a t e d and non- i r r iga ted - .
areas.
*The b r acke t s -show the ranges f o r the r e p l i c a t e s o i l
samples.
Nu t r i en t ( X i n e r a l )
Ni t rogen
Phosphorus
Potassium
Non-Irrigated Area Nsan values( t a b l e 19)
Neg/lOOg
I r r i g a t e d Area Mean values( t ab le 19)
Heg/1 00%
Dif fe rences between t h e two a r e a s Meg/100g
51.615(*28.97-105,396)
0.1135(0.0323-0.2648)
0.2620(0.1125-0.3446)
23.234(+22.984-23.483
0.0484
0.1783(0.1675-0.189)
28.381
0.0651
0.0837
T h i s t s b l e r e v e a l s t h a t t h e d i f . f e r e n c e s i n t h e
c o n c 3 n t r a t i o n . s of t h e s e e l e m e n t s ( n u t r i e n t ) a re h i g h e r t h a n
t h e i r c o n c e n t r a t i o n s i n t h e n o n - i r r i g a t e d a r e a e x c e p t f o r K
a n d H a . Consequent ly it would a p p e a r t h a t w i t h o u t t h e
a p p l i c a t i o n of was t ewa te r t o t h e s o i l s i n t h e s t u d y a r e a , t h e
s o i l n u t r i e n t s a r e t o o low t o s u g p o r t amaran thus SPP. produc-
t i o n . T h i s o p i n i o n w a s conf i rmed by t h e l o c a l f a r m e r s i n t h e
s t u d y a r e a , who a s s e r t e d t h a t t h e r e canno t be any s u c c e s s f u l
v e g e t a b l e c r o p p i n g i n t h e a r e a v i t h o u t was t ewa te r a p p l i c a t i o n .
Such a n a s s e r t i o n is i n l i n e w i t h t h e e x p e r i e n c e o f Chinese
g a r d e n e r s i n Malaya which i n d i c a t e d t h a t by u s i n g l i q u i d manure
( w a s t e w a t e r ) , good v e g e t a b l e s can be grown on poor s o i l s
( A r t h u r , 1965).
Tab le 23 shows t h a t t h e d i f f e r e n c e s i n t h e m i n e r a l
c o n t e n t of t h e samples from t h e t r e a t m e n t s were n o t c o n s i s t e n t .
The v a r i a t i o n s i n m i n e r a l compos i t i on would a p p e a r t o i n d i c a t e
t h a t t h e l o c a t i o n o f t h e was t ewa te r i n t h e t r e a t m e n t l i c rks
w e l l as t h e r e s i d u a l m i n e r a l c o n c e n t r a t i o n i n t h e s o i l a r e
i m p o r t a n t on t h e e f f e c t o f t h e was t ewa te r on c rop . Consequen t ly ,
t h e z a g u l t o f t h e a n a l y s i s r e v e a l s t h a t w a s t e w a t e r a p p l i e d a s
i r r i g a t - i o n w a t e r c o n t r i b u t e s e s s e n t i a l m i n e r a l s n o t o n l y t o
t h e s o i l b u t a l s o t o t h e crop.
CHAPTER SIX
CONCLUSION AND L ~ ~ C O ~ ~ ~ U ~ ~ ~ . ~ T I O N S
T h i s s t u d y i n v e s t i g a t e d t h e use of wastewater from t h e
- U n i v e r s i t y o f N i g e r i a , Nsu!&a (UN, Nsukka Campus) wastewater
t r e a t m e n t works a s i r r i g a t i o n water source. The p h y s i c a l , .
chemical and b i o l o g i c a l c h a r a c t e r i s t i c s of t h e wastewater
a t t h r e e l o c a t i o n s of t h e t r e a t m e n t works were e v a l u a t e d , The
p h y s i c a l and chemical p r o p e r t i e s of the s o i l of t h e s tudy s i t e
which h a s been under wastewater i r r i g a t i o n f o r some t ime now
a s w e l l as t h e minera l composi t ion of wastewater i r r i g a t e d
amaranthus SPP v e g e t a b l e were a l s o eva lua ted .
The wastewater c h a r a c t e r i s t i c s snowed t h a t t o t a l s o l i d s ,
BOD5, he lmin th e g g s , protozoan c y s t s , e l e c t r i c a l c o n d u c t i v i t y ,
phosphate , s u l p h a t e , c h l o r i d e , ca lc ium, magnessium, potassium .
and sodium/sodium a d s o r p t i o n r a t i o were h i g h e r i n t h e wastBwater
and s t a t i s t i c a l l y d i f f e r e n t from s i m i l a r c o n s t i t u e n t s ( e x c e p t
t h e n i t r a t e and s u l p h a t e ) of t h e domestic water supply ( t a p
wa te r ) of t h e U n i v e r s i t y community. S t a t i s t i c a l a n a l y s i s a l s o
showed s i g n i f i c a n t d i f f e r e n c e s i n t h e means of BOD t o t a l 5 '
s o l i d s , and e l e c t r i c a l c o n d u c t i v i t y between t h e i n f l u e n t and
t h o s e of t h e i n t e r m e d i a t e and f i n a l e f f l u e n t s , i n d i c a t i n g t h e
e f f e c t i v e n e s s of t h e t r e a t m e n t ponds, There were however no
s i g n i f i c a n t d i f f a r e n c e s Setwsen t h e c o n c e n t r a t i o n s of t h e s e
e l e m e n t s i n t h e i n t e r m e d i a t e e f f l u e n t and f i n a l e f f l u e n t
which shows t h a t no f u r t h e r s i g n i f i c a n t t r e a t m e n t on t h e s e
c h a r a c t e r i s t i c s o c c u r s i n pond 2.
The w a s t e r a t e r w a s found t o be c o n s i s t e n t l y s a l i n e a t
t h e t h r e e l o c a t i o n s of t h e t r e a t m e n t works w h i l e t h e SBR, t h e
i n d i c a t o r o f s o d i c i t y , w a s low. The combined e f f e c t o f
s a l i n i t y h a z a r d and s n d i c i t y h a z a r d de t e rmined from t h e
' U S D A c l a s s e s o f s a l i n i t y and sodium h a z a r d f o r I r r i g a t i o n
Water ' is however low, i n d i c a t i n g t h a t t h e was t ewa te r ( raw
and t r e a t e d ) i s good f o r i r r i g a t i o n i n t h i s r e s p e c t . Evalua-
t i o n o f t h e pa thogen ic organisms c o n t e n t showed t h e p r e s e n c e
of h e l m i n t h eggs i n t h e i n f l u e n t i n t h e o r d e r of 20 t o 60
t i m e s h i g h e r t h a n t h e r e q u i r e d maximum c o n c e n t r a t i o n f o r was te-
w a t e r i r r i g a t i o n . The i n f l u e n t and t h e was t ewa te r i n pond 1 '
is t h e r e f o r e t o o p o l l u t e d t o s e r v e as i r r i g a t i o n !water s o u r c e
and s h o u l d t h e r e f n r e n o t be used as i r r i g a t i o n water . The
i n t e r m e d i a t e and f i n a l e f f l u e n t s were however f r e e of he lmin th
e g g s and c o n s e q u e n t l y c a n s e r v e as i r r i g a t i o n water . The
c h e m i c a l compos i t i on o f t h e was tewater r e v e a l t h a t i t (was te-
w a t d r ) i s a ' s to re -house1 o f n u t r i e n t s f o r c r o p p roduc t ion .
d a s t e w s t ? r i r r i g a t i o n i n c r e a s e d t h e w a t e r h o l d i n g
c a p a c i t y o f t h s p redominan t ly sandy s o i l and t h i s i n c r e a s e
was l a r g e r a t t h e t o p l a y e r ( 0 - 10cm) of t h e s o i l . The
c h e m i c a l a ~ n l y s i s of t h e s o i l snowed s u b s t a n t i a l d i f f e r e n c e s %n
between t h e :daatewater i r r i g a t e d a r e a and t h e n o n - i r r i g a t e d
a r e a , w i t h t h e i r r i g a t e d a r e a h a v i n g h i g h e r c o n c e n t r a t i o n s
of c h e m i c a l c o n s t i t u e n t s . These d i f f e r e n c e s were i n t h e
o r d e r o f o v e r 2 0 W f o r e l e c t r i c a l c o n d u c t i v i t y and magnessium;
o v e r 10% f o r N i t r o g e n , phosphorus and ca l c ium; 92% f o r
c a t i o n exchange c a p a c i t y (CEC) ; 45% f o r po ta s s ium a n d 6% f o r
sodium. These h i g h e r c o n c e n t r a t i o n s have n o t c a u s e d s a l i n i t y -
o r s o d i c i t y problem i n t h e s o i l . !{astewater i r r i g a t i o n would
t h e r e f o r e a 2 p e a r t o be a means o f r e p l e n i s h i n g needed n u t r i e n t s
i n t h e s o i l t h e r e b y c o n v e r t i n g a n o t h e r w i s e poor s o i l i n t o a
f e r t i l e one f o r c r o p p r o d u c t i o n . Consequent ly was t ewa te r
i r r i g a t i o n i s recommended as a s o i l improvement p r a c t i c e .
The p o o r per formance o f t h e amaranthus SPP. grown i n
t h e s t u d y a r e a and i r r i g a t e d w i t h domest ic ( p o t a b l e ) w a t e r
s u p p l y ( t a p w a t e r ) shows t h a t t h e s o i l i n t h e s t u d y a r e a is
t o o poor t o s u p p o r t p r o f i t a b l e v e g e t a b l e ( amaran thus SPP)
p r o d u c t i o n . The s u p e r i o r growth performance under w a s t e w a t e r
94.
i r r i g a t i o n i s t h e r e s u l t o f t h e d i r e c t c o n t r i b u t i o n o f
n u t r i e n t s from t h e was t ewa te r a p p l i e d and t h e r e s i d u a l - -
m i n e r a l c o n c e n t r a t i o n i n t h e s o i l from t h e p a s t was t ewa te r
i r r i g a t i o n p r a c t i c e i n t h e a r ea . It would a l s o a p p e a r from
t h e m i n e r a l o g i c a l a n a l y s i s of amaranthus SPP. l e a v e s t h a t
t h e l o c a t i o n of t h e was t ewa te r i n t h e t r e a t m e n t works is a n
i m p o r t a n t f a c t o r on t h e o v e r a l l e f f e c t o f t h e was t ewa te r
on t h e m i n e r a l compos i t i on of t h e i r r i g a t e d c rop .
1 . The u s e of t h e was t ewa te r from pond 1 as i r r i g a t i o n
w a t e r s h o u l d be s topped . T h i s is i m p e r a t i v e i n o r d e r
t o e l i i n i n a t e t h e p o s s i b l e t r a n s m i s s i o n o f h e l m i n t h i a s i s
( t h e h i g h e s t h e a l t h r i s k from was tewater i r r i g a t i o n )
T h i s is a l s o s i g n i f i c a n t because the d i s e a s e s which can
be a s s o c i a t e d w i t h was t ewa te r i r r i g a t i o n a r e endemic i n
Nsukka town.
2. I n view o f t h e b e n e f i t s d e r i v a b l e from was tewa te r
i r r i g a t i o n i n t h e s t u d y a r e a , i t is recommended t h a t
a t h i r d pond be c o n s t r u c t e d e i t h e r i n s e r i e s o r i n
p a r a l l e l w i t h pond 2 t o s t o r e s a f e and unused was tewater
* e f f l u e n t d u r i n g t h e r a i n y s e a s o n f o r u s e i n t h e d r y
season. Since vegetables are the least suitable
crops for wast'ewat er irrigation on health ground,
- there is the desirable need to encourage or enforce the
cultivation of alternative crop(s) under wastewater
irrigation.
3. There is the important need to determine the
E' Coli bacteria content of the wastewater to certify
whether or not the wastewater in pond 2 is really safe
for irrigation (in line with Shuval et a1 (1986)
recommendation).
4. The significant nutrient content of vastewater, as
revealed in this study, suggests that wastewater be
recommended as a source of nutrients to complement (if
not replace) chemical fertilizers for crop production.
'9astewater irrigation certified free of health hazard,
may serve as soil improvement practice on very poor
soils.
5- An epidemiological study of diseases that are
associated with wastewater irrigation (such as typhoid
-fever, diarrhea, dysentry etc) should be carried out in
Nsukka town. Such a study should attempt to correlate
such occurences with the consuaption of wastewater
irrigated crop products by the public.
96.
6. .A l o n g term ( a t l e a s t twelve ca lendar aonths)
c o n t i n u o u s a n a l y s i s and e v a l u a t i o n of t h e was t ewa te r
c h a r a c t e r i s t i c s i n c l u d i n g t h e d e t e r i n i n a t i o n of h2avy
m e t a l s s h o u l d be under taken . Heavy m e t a l s i n was tewater
i n e x c e s s amounts can be t o x i c f o r i r r i g a t i o n pu rposes .
Cont inuous e v a l u a t i o n of t h e s o i l p r o p e r t i e s w i l l
r e v e a l t h e i n f l u e n c e ( i f any) o f t h e s e a s o n s an t h e
e f f e c t of was t ewa te r i r r i g a t i o n on t h e s o i l p r o p e r t i e s .
7 Designed expe r imen t s s h o u l d be c a r r i e d o u t t o
de t e rmine t h e e f f e c t of v a r y i n g amoun t s . of was tewater and
. combina t ions o f was tewater and p o t a b l e w a t e r as i r r i g a t i o n
w a t e r on c r o p y i e l d and q u a l i t y .
Agus iob i , O.D.. (1976) . Sewage Trea tment P l a n t at t h e U n i v e r s i t y of N i g e r i a , Nsukka, 3 8 ~ . Unpublished 3 . 3 . P r o j e c t ~ e ~ o r ' t p r e s e n t e d t o t h e Departf ient of C i v i l E n g i n e e r i n g , U.N.N.
American P u b l i c H e a l t h A s s o c i a t i o n , Gae r i can Waster Yorks A s s o c i a t i o n and Water P o l l u t i o n C o n t r o l F e d e r a t i o n (1971). S t a n d a r d Methods f o r t h e Examinat ion of l a t e r and idas tewater . 7 3 t h ed. BPiIA, XiWA and 'iIPCF, New Y ork.
Arar, A. (1987). I r r i g a t i o n w i t h sevage e f f l u e n t : I ts a p p l i c a t i o n i n t h e Near E a s t ( V e s t e r n ~ s i a ) . ';dater Q u a l i t y B u l l e t i n , 1 2 ( 2 ) PP 51-58.
A r t h u r , T. (1965) . Garden ing i n Hot Count r ies .207P, Faber and Fabe r .
Barngboye, O.A. (1986) . Re-use of sewage e f f l u e n t f o r s u p p l e m e n t a l I r r i g a t i o n o f 2a i ze .Pape r p r e s e n t e d a t t h e N i g e r i a n S o c i e t y o f A g r i c u l t u r a l E n g i n s e r s i N a t i o n a l , 1. Conference a t Obafemi Awolovo U n i v e r s i t y , I l e - I f e s e p t . 3 - 5 , 1986.
-:.
Benneth, Y.F; C. J a y n e s and C. Harvey (1973) . E f f e c t o f sewage e f f l u e n t on c e r t a i n chemica l c h a r a c t e r i s t i c s of s o i l , p r e s e n t e d a t t h e 1973 Annual j o i n t mee t ings of ASX, CSSX and SSSh, Las Vegas, Nevada, Mov. I 1 - 16, 1973.
B o l l , R ; H. Dernbach, and R. Xaywer (1986) . Aspec ts o f Land D i s p o s a l o f 3 a s t e w a t e r as e x p e r i e n c e d i n Germany. X a t e r S c i e n c e a n d Technology Vol. 18 Nos. 7/8 PP. 383-390.
Bond, 2.G; and C.P. S t r a u b (1974) . Handbook o f Envi ronmenta l c o n t r o l Vol. I V : Wastewater: Trea tment and Di sposa l .
.. 905P CBC P r e s s i n c ; Parkway, C leve land .
Bouwer, H ; and E. I d e l o v i t c h (1987). Q u a l i t y r e q u i r e m e n t s f o r I r r i g a t i o n w i t h Sewage Yater . J o u r n a l o f I r r i g a t i o n and Dra inage E n g i n e e r i n g 113(4 ) PP 51.6 - 535.
Cromer, R O N ; D. Tonk ins ; N . J . B a r r and P. Hopmans. (1984) . I r r i g a t i o n of Monterey P i n e w i t h Yas t ewa te r : S f f e c t on s o i l chemistry and groundwater composi t ion . J o u r n a l o f Znvi ronmenta l !Qual i ty 1 3 ( 4 ) PP 539 - 542.
Day, A.D.; J.A. Ncfadyen, T.C. Turkey and C.B. C l u f t (1981) . E f f e c t s o f ; 4 i n i c i p a l was t ewa te r on t h e y i e l d and q u a l i t y o f c o t t o n . J o u r n a l o f Env i ronmen ta l q u a l i t y Vol lO(1 ) PP 47 - 49.
G r e e n s i l l , T.M. (1964) . Gardening i n t h e T r o p i c s . 272P. Evans B r o t h e r L t d ; London.
I s r a e l s e n , O.W. and V.E. Hansen (1962) . I r r i g a t i o n P r i n c i p l e s and P r a c t i c e s , 3 r d ed. 4 4 7 ~ , John ! i i l ey and Sons , Inc . N e w York.
X e t c a l f and Eddy, Inc . (1972) . J a s t e w g t e r E n g i n e e r i n g : C o l l e c t i o n , T r e a t m e n t , D i s p o s a l , 782p, McGrnw-Hill Book Company, New York.
Michae l A-hI - (1978) . I r r i g a t i o n Theory and P r a c t i c e 8 0 1 ~ ~ Vikas P u b l i s h i n g House, New Delh i .
M i n i s t r y o f A g r i c u l t u r e , Food a n d F i s h e r i e s , London (1977). Hanual o f V e t e r i n a r y P a r a s i t o l o g i c a l L a b o r a t o r y Techniques . T e c h n i c a l B u l l e t i n No 18 , London 8:450.
Morten, G.C; Y.E. La r son and C.Z. Clapp (1980) . X f f e c t s o f Mun ic ipa l ! i a s t ewa te r e f f l u e n t o.n per formance and f e e d q u a l i t y o f maize vs . Reed c a n a r y g r a s s . J o u r n a l of Env i ronmen ta l - q u a l i t y . Vol 9 ( l ) PP 137 - 141.
P e r c i v a l , NOS. (1984) . P o t e n t i a l f o r i r r i g a t i n g k r a f t pu lp m i l l e f f l u e n t o n t o f a rmland i n t h e C e n t r a l North I s l a n d , N.Z. l a t e r and S o i l M i s c e l l a n e o u s p u b l i c a t i o n No 70 PP 257 - 266.
P f a f f l i n , J.R. and 3.N. Z i e g l e r (1976). Encyc loped ia o f * ' Env i ronmen ta l S c i e n c e a n d E n g i n e e r i n g , Vol. I , 6 0 0 ~
Gordan and Breach S c i e n c e P u b l i s h e r s , New York.
S a b e r , M.S.N. (1985) . p ro longed e f f e c t o f Land d i s p o s a l of human was t e s on s o i l c o n d i t i o n s i n T r e a t m e n t , D i s p o s a l and Nanagemont of Human Vas tes . 'da te r Sc i ence and Technology Vol. 18 Nos 7/8 PP 371 - 374.
S c h i r a d o , T.11 Verga ra , 3.B. S c h a l s c h a and P. P r a t t (1986). Evidence f o r movement of heavy m e t a l s i n a s o i l i r r i g a t e d w i t h n n t r e a t e d was tewater . J o u r n a l of Env i ronmen ta l Q u a l i t y , 1 5 ( 1 ) PP 9 - 12,
S h a i n b e r g , I. and Z.D. O s t e r (1978) . 4 u a l i t y of I r r i g a t i o n 'da te r . 6 5 ~ , i n t e r n a t i o n a l I r r i g a t i o n I n f o r n a t i o n C e n t r e , Bet Dagan. -
S h a p i r o , L. and W.J. Brannock (q962) . Rapid A n a l y s i s o f S i l i c a t e , c u r b o n a t e and Phosphate 2 o c k s . 5 6 ~ ~ U.S. G e o l o g i c a l Survey B u l l e t i n 1144 - A . U . 3 . Government P r i n t i n g Off i c e J a s h i n g t o n .
Sharma, V.K. and B.D. Kansa l (1984) . E f f e c t o f n i t r o g e n , fa rmyard manure, town r e f u s e and sewage wa te r on t h e y i e l d and n i t r o g e n c o n t e n t of maize f o d d e r and s p i n a c h , I n d i a n J o u r n a l o f Ecology l l ( 1 ) PP 77 - 81.
S h u v a l , H . 1 ; A. Avner, B. F a t t a l , E. Rawitz and P. Y e k u t i e l (1986) . ' da s t ewa te r I r r i g a t i o n i n Developing C o u n t r i e s . 3 2 4 ~ . The ' ; iorld aank , ' J a sh ing ton D. C.
T e s t e r , C.F. and J.I. P a r r (1982) . I n t e n s i v e v e g e t a b l e p r o d u c t i o n u s i n g compost , , P a p e r p r e s e n t e d at t h e 7 4 t h Annual N e e t i n g s , XSA, CS34 and SSSA. Anaheim, C a l i f o r n i a , Nov. 28 - Dec. 3, 1982.
Thorne , D - d . and M.D. Thorne (1979) . S o i l , ' da t e r and Crop Production.353P. A V I P u b l i s h i n g Co. Y e s t ~ o r t , Connec t i en t .
T roeh , F.R; J.A. Hobbs and R.L. Donahue (1980). S o i l and Y a t e r C o n s e r v a t i o n f o r P r o d u c t i v i t y and Znvi ronmenta l P r o t e c t i o n . 7 1 8 ~ . P r e n t i c e - H a l l Inc . New J e r s e y .
Whi te , J O B o (1970). The Design of Sewers and Trea tmen t ',iorks. 3 1 8 ~ , S d r a r d h o l d ( P u b l i s h e r s ) L t d ; London.
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