V3I2-

WATER TREATMENT SYSTEMS AND THEIR SUITABILITY FOR

GRAVITY FED RURAL WATER SUPPLIES IN MALAWI

LIBRARY I . , .•••• Clonal Befersnce Csntre lor Community Water Supply

I r . H .P ;J . van Schaik

Ju ly 1983

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a auch bc;tt-.:i- ana h ia / ie i - s e t t l i n g e i i i c i r - n c y t h a n a eoav a r : t i c n a l

seci.~e-!.t t a n a , and v.naa f o r t n i s roc.-.o';i t e a a e o en it;.- o f a i c i e n c y

of s i l t rea .ova l f o r ana a v ^ i l a . v. r-rctr.

r.'j-Jl-I t S

I;-; c- e a a l u o n t c i the- t i l t e d n l a v e aet t lc . ; . . ,^na i i : .. ;vcr-, &. ;;.^;vv: ;

cvc-i. a p e r i o d c i j> y e a r a .

I t v a s .iOticeci t u a t t oo p l a t e n a c c a n u l a t t . a ' .". a. at, c i .'.a. a t

anrir , .y t h e r a i n y n t a ^ o i j , t u t t n a t t h e e i ;• i i . t . . t r u d i t ^ uud

•;ct : x t i c a a l \ i . a . rovec j f ; t r } • a a a i n.u t a i 'Oi^ ; . t.,_ S ^ U ^ r .

'i'l.t v i a i V . i i i t y a^°a. . r a - . - i n c a u n c - a n ^ e o .

, . . , i . re . ^ i t i r DO.; _.or Loa* -.y a n a t c n a c t Li £.;•.• a .at : A , : ; ; : i..aa. t i n

a ;.. :V.K>», J. a, c^ i i ; ^ c ; . ' uf :•..<; />*.! v/iacn was f i i i o d v.i i; . r a v

'. i 'Cti ( v i .-i L i ! : i t ) and t •..'..,.rti; :t'.... ta ; .n i cm; ana v/nicti wa;. a ^ c ; t:.

•„ti.it. i o r n ^.-no:: tn HGVfei'ai w o ^ a s . •'. J. Lv*;i'' / ' I t ' t : b t : :Cr O J. j . L I.

v.'it:: a 3Uper; 'iatai; o v a i c ; ;

,>-."j f..etoied down to t ; .e h-'~0 :-i :<..i±r..t

v.:ao a t i l l r e o o i a h r.-rov;.; i n ^ O i O / ,

A'h c l e a r . The v i a i o i l i a.;t:. o i t a o i s a a t a a n vj crc, Wiiich i o n o t aca_i. a taLd t a. a r s \ ' ; a ..or

a l e v.- aano i i l x r a t i c n .

- t _ .

c io j .uaica a.Via. i'c'ccr/':.:aaciatxai";

eciisr. e.-

'u;--j'n. \ . l t i . ca . t a.'.y a a v i a a to i..j.aa.va X:.'. a y o r a u . i c r e 0 i a a i-.\.z

a r o v a n to ': c- a.c.*.]-<£.te i c r t a c a a v o v a l o i aana ana c . r i t .

'. t i l t . ?C . : i a t o i G t u e r • . ; i l l : ; e r : ; o a . t l .o cafiic i n a c t i o a i.. a

.-:;:. a i l a r v o l a a e , i.. ;.; i a caca i . c r to co,. ; ; t r n n t .

..a; •: •/'•:•„• a. . ; o i t o n o;: t.t a a tuaa . a Co : ; a a v a i c . . . . a a a o t .

ft

. o t ; ; co*jVf;.'i t.j Ci'ifil .<• ^u i : . .-.•.• .'it ti-.u

i i; ! . o x : . ; i.-.i j. J. i.' l . , c

J - -; - i - j • . . . •) . . *

: ', 1 -J • • > • - . • - ' • "' > • • , - • . ' • • • ! + -"

o i . ' . L ._• ' . ' . . i ^ 0..'? i/. ; v. J. i.?..! i..>j-J. 1/ J . . . 1 o . I ' - ;

:.'• _;. i'J J.

.'.'i j.v\ :.r;:•.-.. L: . ,}',;i¥c d i s e a s e d sk^iivi&ii to.tio:i tcci.ui'./L.c.. i ; . : t j : c : . ".v;; c a r r i e o ou t i n i'ne ^ u i t ^ b i l i i . ^ c i .-.i.cw;: :•.. J i xr^tic-"- t..j;..':i __•:':. r i c r trie removal oi' i^c i i ^ e •. ..!it i/i X:je ri;v v ^ l c r , I ' - ree ::-, .::"ie:.'<£ were t e s t e c - 3>. ;.••!• ..ci'ii.-.c-iit:.! n o w , coa r se L:ravel f i l t E E t i c n

f i O . . f i l t r a t i o n through a course stuio ::ea

lew o^;:d f i l t r a t i o n tiirouaii a f i n e oiuo i.,eu.

f, ••:•-• b(.:;•-zioatzcv.-..-;. o: I.' Ot-J. ^_L o_L j i&e c i . ? t r i Lurion ere e-ndix Z).

;>. ;• . ! . i . o r i s o n t s l I'iov; Coarse t r a v e l i*il t r a t i o n .

- ce:ii . ii gnj uj;ta nee i;ia;\rar..;t,e t>. £OAU5 IC4M- JVM.

•OUT. =4 te? V ^ P O M ^ C ~Li ^- l y j MO^ j j d : 2JT_ _ J M ? ;

H k.o

' 7 / i i r ) ( i iov;)

.;.:"... - ' ;.j/hr ( s u r f a c e icadir- ; ) Oro;:V, .•; a c t i o n a l su r face a r e a = 0,

- L i t e r a t u r e reco:;.:.anaation :i.:t i i oz i i on t a i flow, coa r se g r a v e l r r c i f i i t r a t i u ^ t echn ique i:i i"':C-J:V:I.>JIKIej a?, a t e chn ique to r educe t n t t u r o i c i t j of . u r i a c e ».:.tt-rc i:.e.-j up above IsO J To (J •i.c-.soi; XarLidi tv '..••;-ity) to LC1O\, ';'..• 0 i'L>. l e t f i l t c r r u a b a i e r e ^ o r t g j to •:.-... ;..-.• io.; u:.. ...••.. • :.io.l i 'v.ars, ( ) .

- ^e.ui . l ;::

.....v.-.:- , ^ :.. .. --i;..i ;. 1:* O i .L •. •:' . u.UVi i c:.. V i O C - . o o

; \ , l ' Ll O t ' - : :.'<.• u- u:'..;."l v , i \.:.

- 7 -

: V i . - - i f . - i J . i t ; . . >• ' : ; . t . . ; . . - ; ; r j i y i o . " : ; . . "C : -C- VJ 0 1 X; ;C r;,."». V v a t i r .

.i'* a'jc'i t i C i j , x..c iio>- oic :j'ia. cc-u^io i.-i-a';.,!^ u i ' t t r a

:V.-' h o u r s c i ? a i . ; .

i , t l C :. >;' J C . ' •! i J J. C'.< ix . ! ' . ' l : ;C , ci-i. v -'. 1" i ' V C i ' j - i . : : i .O'. ••:•!

X:K:., ';> I:. I I ; L : ti-, > . t: cjaye \-,i^icrt i : :ol; . 'oec oi ea : . i :^ c a t

x.!'.;c xry.'i'.f \.\'„-i.i :•_ i i .e l i l t c r b e - d u i a t c i i a l a:.':; i \ . i i . ' . . i . j^

out iarii:. •

.'J. •'.' .':'. 1 J T. V-o." . X.V:' '-..0. i ' i 4 J ; _ X Xl .Z 'O Uj_,;'i Ll:(if i i j . ! / 6 r , ] : It.- X i i t

ii.'"-.-;.} !;c...-i'.-rr"...-,.-'.i'L, :..Lic"h hiacie 'the . c l a a u i i . ^ cv.;crcif.e so

i L C I i.'.OU 'I .

o 0 ; i c l i ' c l o a a.id rtcc>:.'i,;.-eijoation

i i . i s :.;trti'ioci Oi - i l l t r a t i c ' i ' i "wLich o] /e ra tc -s \ . i t n vex-j' Vi?,

p o r e voluiiieo a.;ci :.iesii o p c u i t : 0 e re;;'>ove.-i s i l t i i a ^ i c a l l y

u . rou; ;h aosC2 \ t i o . i ex xhe t i l t p a r t i c l e : ' ; u,; ^o xi..-;- c . i ^ . e c

j i o n e ; ; a r i o c e c a -c t a . o u ^ a s e i i t i s a x a t i o ; ; .

*LC i n c r e a s e i;': i.- oi i 'i c i e!:C£ o i t i . i i ; ov. f.xei. <--. v«.--'<ti^ xo;.« i.i'C0

i o . fiir^.. j-.-iOLiir". x-e ]..-rectified ( s ay i n trie or-ii&r of -J . i - . . / \ . r ) .

j-;o-.-. cv&;•"-, i . ; i . v.o;.lc: i n c r e a s e - t u e r o c u i r e c i volume i . i t u ^

i a c t o r 1 0 .

alx. .cur:k -ti.-c i i ...-_• v.:\-i- tii i i e i ericy v / i l l t i i aa l i K t - l j i n c r e a s e ,

i t i:- . i t i l i '-.-.;. ••'.v-'^LxiuI i f t : .e e f f l u e n t q u a l i t y w i l l ':••_

,^ot.c c'i.c J _.i. i o : ..: c- ii-^.. i t i i ' i ic a t iov/ tfiiu; i i i i s r ,

j. i: a c i a i x i o a , t..-. i ; . . o u x r e q u i r e s to c l e a n t i .

e l y a i x e r s- v t r d > t. •:..-..';. i r . i ; ,

o r s i.'la':it •-•>i . ^ «'i- !„ ' . ; . ^e r I. : l e v ; -:X.-;e'.it c o s t

f o r th ic i i i i x e r i i : tnor;-.oiic-.

j.-'cr aL-ovt. re;.-.3C.'ii i t i s <.c-x re cc;a .\,..c.: i - Xu u.>.e iioris&i'jXal

IX cor;;; u i t c . , •_..!. x. .c-*.a,u V: i x.'. ; .-" i-.-i.ul''. . v i - : . ; \ i -• Xi

"I

f l e w , c o a r s e L'.r.-. x ' u . i i l o r . r u i , a „ir;c:j j,xe.v L> K*. . . i k . 1 l C r

' > . ' ^ . i . ...low o'aati f i i x r a t i o r

u u o a. 1-, i . . : - w 0 ; - . X i x P'i 'Awtf#t iHc i

"r~'i J v f ' i ' V K ^ T t V v

: .. f«-ftm!nOs._(j<£_.,'j ' ; •; • . . . .i! ?

Ts-T ••;': i v ? \ - i t 0 N i

H ! [1J! • I - !! !• II i. «(

i: i-1-

- o

F = b u t t e r f l y flow control • G - bettors i n l e t H = prevention negative pres I = ef f luent , to sun;p J = e f f luen t to waste.

A = raw water i n l e t B = overflow C = supernatant drain I> = drain of eff luent E = flow ^easureinent device

fkc 2c:..oa r i l c t p lan t f i l t e r s were 4 in number p a r a l l e l tanks accomodated within a c i r c u l a r tank (diameter 7.5 m), ^ vised in to 4 compartments with d i* idin C w a l l s , v i . u

surface areas of 10 ra^/filter. The. actual design o d i f f e ren t iron the general design as i s shown in IHagrawrae 8.

Dis.ijra.^ne 8 Zomba i i l o t l]_ant lay-out .Slew cand iMl te r t

>f the Zcifba l i l o t P lant was s l i g h t l y .» T;ia£:r amine 7 , and

//

/ /

/ /

L t w

\

\ \

X

45

! r

*m TT

U •?.St>o

\

>

'.

\

1

&*

e%

-fl:

, f c ^ _ : " W

B-

J 100

9"

iCUx>

}a> 100

11<*>

iA3

,l- ^ K / > , »V'r>.

r ( . - i L j t

isoo

t~-i ^ ..a ,*

• /

fi

*-t

0 1 ~J f

tn

^

1 i i

L.____.._fj;

i ~ v . C-"VXAJ

erff ^ A ^

l i t e r a xur e r e cornic end a t i o n

Due niov: sand f i l t r a t i o n i t t h e p r o c e s s b^ whic:;.. i .^i^i it; p u r i f i e d bj' pabein^ i t through a porous a a x e r i a l a t re . t e j c i 0 .1 - 0 . ; J i^/nr.

.i.-ne to xat f i n e j_.rain s i z e the i o r e ^ oi the f i l t e r beu a re

tssiall. -The suspended' m a t t e r pree-enx ± ri t he raw water a re

iarwel.> r e t a i n e d i n the upper few c n ' e of tue i ' i l t .;i:. -_u.

'i'iii.- uliov.-e the ' i f i x e r to be c l t a n e a b} s c r a p i e o.-._., x:;^

icy J. aj-v.-r oi sand. ..\c ioi. r a t e : : of f i l t r a t i o n i r e u_ed

t.-ic. i n x n r v a l e between two t u c c e t u v e c l ean i r v ; n v.ilj. b-i,..ixi.,y l 0 . = w .

int. i-;_a.;i p-ar^ose of slow sane f i l t r a t i o n i ; xhe r-.;. .v.-\ .J. ex pntno^ii . ic: o r b a n i s ^ s i'roii; the raw w a t e r , it . ; .arxicn2v.i uic wacccrio and v i r u s e s r e s p o n s i b l e io.i tne Kpre^dinw cf 'i.'ute:. id_a teo d i s e a s e s ( ) . ^lo-.• ci.:.: l i J t r u t i o a i s an e x c e l l e n t ..;;b,oci o i •i,;..;;;r

X r 6 9 t.',. c i i X 1 0 2'

olow f-jana f i l t r a t i o n provide..- a t i n g l e :'. t ep treaxia&wt l o r row \vhU" not exceeding a t u r i j i c i t.v of !?0 inOl ( ) .

U"ai waxer ouppi i «3 ( j .

j;xp-o rii-:-enxs

: i ten tt-i:tin;. ano improving x:.e i.lc>'«- Hand i ' i l to- r r ia l . t bar ; •;;..

1'.-•;•! t/:«b r e a l VCCXG VU.!C done ni:joe l > o 2 .

.•• oOj.;..'a-r:;. ion v^ii .:,;.ce cetv/een ans ieved fiar^be sat.a •_.•:• iiu~f; v^c — \-' O C.-L i iourio.

10 -

• ; .- , i .Lj j e c ^ i ' i j . : . . b c r c ca:.ei'j o r

- e f f l u e n t i'lir-. aa i s ; e n u r e d I re ; : ; t h e e f f l u e n t p i p e t ; i n l/r.:iri

- i n f l u e n t ?;::,.. ; j i : : . a e a t v i s i b i l i t y d e p t h i n en.. - •ii^-j;..~:J-x--i :^:.c Io:.L-ec o v e r t h e f i l t e r s

Vo );:•?. .-..••c.-iS r i or :=..;. cc.-li c o u n t s w e r e t a u e n o : dot:'; tr ie rt;.v.;

> ; ; . t t r ana ti.<.- e i i l u e n t s .

i l t o

X;-.bI.» 3

'i'au.-c f i l l e d w i t h c o a r s e r i v e r saud

Huti :

Day a

1

r

•

4

. D u r i n g r a i n s a no \

V i s i b . a e v -1 h ( c rr:)

rav; w a t e r

< 5

< 5

20

e f f l u e n t

> 50

> 50

> 50

; i t h iov; : Flow

(m/hiO

0 . 1 4

0 . 1 5

0 . 1 1 .. J

2'lev." v e l o c i t y ] r e s s . nea-j ."

( C M )

60

52

105

.OUO

Ajfter day 4 f i l t e r r u n was s t o p p e d .

Ivun 2 iJurir i :-; r a i n s v ; i t h h i & h f low v e l o c i t y

<;ay

1

k

>

' r

«/i s

rs.v.

< 5

10

25

yo

i b i l i t y d e p t h

( c a ) e i f l u e i r

> 50

> 50 •

> 50

> 50

Flow ; ( i r . /h r )

0.4-fc

0 . 4 0

0 . 2 5

0.1-3

"i-'res ;>ure ::£

157

102

255

24 5

ac ].o-'-:-

i - i . i » w i ' Li o. 4 filterrun vat- sto-ppec, and filter clea;

5 ..iter rains and vitn iov.- fie-; velocity

i ;ay

1

52

Jo or

v i s i b i l i t y d e p t h

3-i.v (c<n)

15

, c . f t s i tlic

e i i ' i u e n "

> 30

> 30

f i l t e r v

• - • •

rlO'v.

. (C.T.) G . l l

<" ' "i ; ' t

.'as c i t

i e . : ; u r i head Lo^b

(cni)

35

janed .

:';.u. i i l r e d w i t h f i n e s a n e froirj da ' ibo

1 - 'w'riu- r a i n s w i t h low f low v e l o c i t y

- • • - . v

1

\ i i i l o l i tj d e p t h

r w (c i i i )

< 5

e f f l u e n t

> 50

> 3 0

fiOW

U/Lr) 0 . 1

0 . 0 6

} ' res ; ju re head Lo;.\_

(cr/,)

136

l b 5

. . i O . J •-* - . . ) < -? o p e r a t i o n was s t o p p e d an--;; f i l t e r c leaned. 0

i..un

3)ay

1 o n

t A f t e r r a i n w i t h i

V i s i b i l i t y d e p t h

raw (cm)

30

1 5 >

e f f l u e n t

>- 30

> 30

ov f low

i'lov;

( n , / h r )

0 . 0 8

.0.06

v e l o c i t y .

P r e s u u r e head

(c».,)

120

250

;.o^---

A f t e r aay 20 f i l t e r r u n was e t o p p e d and f i l t e r c l e anec

Kun 3 . ' . i t e r r a i n w i t h low f low v e l o c i t y

i;ai

1 17

V i s i b i 1 i ty d e p t h

re".' (err,)

"i i .

e f f l u e n t

> . 3 0 > 3 0

F l ov.;

( r c / h r )

0 . 1 2 , 0 . 0 4

1 - r e s su re lieaa

(cr , )

X J J

d J J

L o s s

i f t e r day 17 f i l t e r r u n was s topper : anc f i l t e r c:

Run 4 A f t e r r a i n w i t h l ew f low v e l o c i t y

hay

1

17

V i s i b i l i t y d e p t h

iaw (cm) n r-

1:

e f f l u e n t

> 30

> 30

]?"•} o v ;

( n i / h r )

0 . 1 3

0 . 0 6

P r e s l a r c n.ead j

1^5

ie-0

• C f - S

. '•ft-.r day 17 f i l t e r r u n was s t o p p e d anc f i l t e r c l e a n e d ,

...'ov.. c.!.si?;.".u'

l e e s

T:'. e

t h e

h u r i

ov 1

X:. iki

U i i t n , f i l l e d w i t h dainto sand had s h o r t f i l t e r r u n s ,

d u r i n g the r a i n s and d u r i n g t h e d ry s e a s o n , and the

s f i l l e d w i t h r i v e r sand had f i l t e r r u n s of s e v e r a l

even d u r i n g t h e r a i n s w i t h v i s i b i l i t y d e p t h of T--V- u „ , » <i"d a f l o w r a t e o f a r o u n d 0 . 3 re/hr.

i f f ! u e n t q u a l i t y of b o t h t h e r i v e r sand f i l t e r aiu;

jaVuo sand f i l t e r was v e r y j/ooa

. \ : t h e d iy s e a s o n w i t h raw w a t e r v i s i b i l i t y o.cpth.

. cm tue cajubo sand f i l t e r l a s t e d o n l y around - j

, -..'j.ereas ti;c- r i v t r s a v n ; . f i l t e r c o u l d o p e r a t e ..io r e

,• v.' L, « y 3 •

- 12 -

/

T a b l e 2 x R ^ o ' r . : : A3 :-,(;, CJ. ...'!.•>;J. i ' .o v / i

R i v e r ^ami

.a a t c

i . O

' : : • / *

<•••'.'. s

•. I : <\ 'T

1 2..' -';

'•J; o

flowV U / r i r >

0 . 1 a

0 . -V.:.'

^ • >t>

0 . 3 1

0 . 1 1 i • v

f i l t e r

l o s s ic.n)

20

-"

-,:_";

' r ^

- 1."

20

J.h.abo isi:\:r i

J a t fc

l / ' l i

J . ;.'/ -L - i

Ok/ 2

*•=/ ">

i<;A 1/6

Ihlow

v':.'.-i.r)

0 . 1 1

'-* • — '•

•v • J. 1/

0 . 1 .•.

a • o<.

0 . 1 1

Oil l e r

': lo^rs ( c : j

"! '"0

J. i : •:

x ;••..

UY "i : - .

13>

( O i J C i U S l O U S

1 . Cieaviiri;_ o f f t h e t o p 3 en of t h e r i v e r aaad f i l l e e f i l t e r

a f t e r i t h a s o ioched r e j u v e n a t e s t h e f i l t e r ±\>.:.- r e . t o r e s

t h e Head l o s s to i t s o r i g i n a l v a l u e * TL-IS i . a i c ^ te;>

t h a t ao r e s i s t a n c e b u i l d s up u a d e r a e a t ; ; t a e to_; ',- c::

of t h e l i l t e r b e o , ar.ci t h a t taur. t h e s i l t d o e s n o t

j ' c : ' ; t i t r a t e beyoad t h e top 0 cm.

0 . d ' ieaaia< o f f t h e tor- lev; OILS of w e ua- .ee cav.c ii_l(_c.

i i i l r c t r a i - s o T t r t o r s ^ t h e c r i a i a a ] ' t o l o :

a i t r o u g h t n e f i g u r e d a r c i - f i i j . i t l i :;:or. e r r a t i c , l a i d

:-.ja.y bt c u e ' to t a e p r a c t i s e t h a t o n l y a \ e r y t a i a i e y ^ r

( ;-; J a c a i a a t e l ; , 1 ca c r l e s s ) i s r e a o v e e , aa_. t h a t t . : i . .

:..i^ .-.<_• s t i a a a : l e a v e seine s i l t p o c k e t s ot: t.a;- l i l t e r t c a .

laae v i s i b i l i t y ce ; : t : . ; j of s o t a i i .e r i v e r sand aru. t i e •..'a.-...c

_•<_...d f i l t e r . . ;.:• . r e c o r d e d i a 1. b l e 1 aac; i n d i c a t e aa r t t: ;•

•/uadlity i:-..- v;-rj . ccC f o r bo th f a i l t e r e i h i u e - . t e .

i . a ' . i v e r , a v i e i e i v . s i i._.;,. ; t t u r b i d i t y \\ -?. .r e b s e r v t a ; i . . t i e

r i v e r aar-d f i l t e r e i . l u e r i t , vai ica wui :....;e.. t i r. t . - : .:„..._....•,

c i t h e daia.o e r a ; f i l t e r s , a l t h o u ^ a i t v.ea. r o t t i .Oi i . . to

r e d u c e t h o v i s i b i l i t y d e a t h be low 30 C:-:»

l a a d d i t i o n a c l i e n t erown c o l o r v r o n o t i c e d i n t a e e i h l i

CJ: t a e r i v e r s a n i f i l t e r , \ / a i c h v/as ^ o t s e . ; . i n t i e d:,:-.:.o

>:r.ad i l l v'U'',

; t

V ^ . 1 I ' ... .

e tii ' .v.te o i a

l • - a .:. t:. a \ _ '..

• or to .J'I t Ll e

a a i-..a. OJ. . . l i t carrie."i i:> fi

x . , c ; i a ' i : : . ; C j i i ' H i e r J O I ' a j

- l i -

e. . •„..

E%;'ij.i;":'tr'v;!:a 1 ca-b

0 1 J, to;- ; t i l a n ! C:".. •

xa-.-.- yoi.' v." ;y., e r a t a v i a i b i l i xv c

bno porevoixxa: o: the r i vc r^anu v;aa a e a ^ u r t b

At a peru xraxioi, i.'. (•:•;• th oi taw n i l t of 5 ca i a

i i i . . >

xo XXL i i i i f t i : ; ; .

;?..r:CJ a flov.'rat'j of O.b i:./hr t^e yocv-xiuvie x ' i l l be i:<.li<-:

s i l t a t t a r a ; cay run , ab..aaiix. a v i ^ i b i i i !.>• ;. e. ath of t h a i ' ; b (;.:. C j a T i n U o a ^ l V .

ba i a ouico^y i'ii a r t ; tr;e a a t a l a 'rabl& i .

vAJ.x <X^:.j.X

. ' ' a b l e '.-'. si6'\',i->± \'i C a i / ; r

[ b a t e

1 baw x a t e r CaUuti;/ iuL

i..;J t'J:J'J

bO,bb>b

SO.atO ! \ 09, 9^?

K i v e r a a n ci T i l t t r

:>

JOii.'iXS ICO ax

l b , J ' JU

10 j 1 , 7 0 0

-U 1 a 00

a l i i (:-) :)'-•

'• ' • l .

a 9 ICO,

J.-- - -co :.•: . '.. , i:.x< r | ..o o : :.U..VL-•

i

ib

- 1 ' ' • • ' • • • -

7 ..•,.'

—

i r l . j . ;

-

. «

All oa-urfta a r e tne ave rage of 2 a-a^plec. b e v i a t i o a lroi.j aVt ia^e was aox -'.ore tin.:. ;b_< a , bo ox bay- a tain;, for tne i.umber of c",••;._,-• r- ab c,,;:: a t j •.>

•Jo.'icluoiovir

bae- L c o l i it.;,ov:ii e^j.icie;-cj i s bO b o r ovti' ' bar (.ou, r . •.. r

:~;:ji~ ami tiar^o s:ax f i l t e r s , ano reparole:;;7 ; x..x 1 c. .-T..-. a:

x .-•;•,•. i ' i l te r ra in .

i a c ,nnidi i l xtv l i n c a , v,itn r i ve r sa iu i raaca.<a. <.... ,>;...i«'K..ey

oi ;-: b a l t e r a^aaf 2 months runn i i ra .

J •: i: i r--I.;. v xna o^'.oo oanci f i l t e r nac niL,:.u; ; x . ' ov - l <:-_-. i ci a . c i c

taan fa t r i vuiparic; f i l t e r .

\A: . -I'Jit

.ccal r i v e r A 510'/ . .-..a a'J i l l I t J.' 111: .CO V.'l ".:. COar(: ;c : . - ! i : v.j. ,

caa rci/iove ai<y: s i x t io^ar. vcay e ibia ic- \ .x ly ax a i ic„ : r;

c i O.b " / r . r , ;axa v; i l l i.\d: i> • o\a. a r p r o x i a a x e l y bO ;•• cf

tne paxao ;:.a!ilo^b.

b-r.ria:. tii.:C£ x ::•<:.'. la-, i .r.. vv.:^r v i s i b i l i t y a a x : : aaa j :.

<. i.- i- c 1 O '• " V T I', f l/C r 'a. : : /C' . . . -

(.0. r- c,. o:i.

•/.nt clea:_inL . of t n e sane end t u t r e f i l l i n g w i l l . q u i r e

1 i e L-OUj"t;T ; . & : I . ; r;.e- f o r 1 c; <fj.y f ;\<3 V.' a A f C U l i G i !/. , .G:i;La

or. trie p i j o t > l.-iiit.

: o) s i i t y l i v e r s i t i s recommended to have a 3-h.ase 1

• : :- ic; rc.:.ovc;. the- t u r b i d i t y a s w e l l a; ^u ?-.) /.-. o i thf ••i. u i . ' O , u v> -. \.t f and v;hicfc n h a s e i s f o l l o w e d by P h a s e 2

which should, o p e r a t e a t a f l o w r a t e o i 0 . 1 5 iL/nr t-aid

wiii ch i s ' / ^ i n l y c o n c e r n e d w i t h t h e r emova l of pat . :o^,ens .

A i er .ovei rc . te of 99 ^ s h o u l d he o b t a i n a b l e j,- . . . ;;w.sv; A

<i:ij. t h a t i l l t e r r a n s w i l l r e a c h up t o 2 i i .ont^s arid r a r e ,

b e c a u s e of t h e v i r t u a l a b s e n c e of t u r b i d i t y . .

An o v e r a l l ren .oval e f i i c i e n c y of 9 9 , 9 K f o r t h e a'jove

2 phased t r e a t m e n t sys t em s h o u l d be p o s s i b l e . -

J)ldGbo ,10.':

AbJheb Pi.; oh

.h'hj)A!fIUJ,

; J X ... .ui L o

1)0:

Two p r o j e c t s w i l l DC- d i s c u s s e d wnicn a r e cot : , ,....• .'.c.r

c o n s t r u c t i o n aod need b o t n a t r e a t m e n t p r o c e s s uciorv,

t:..e v. e t e r can be s e r v e d to t h e c o n s u m e r s ,

.wot., example.- wire t y p i c a l e x a m p l e s . 'Dombole p r e f e c t

v . i l l u s e t. .e ho:. :hoie r i v e r a s i t s w a t e r s o u r c e ah iro:. .

.-p. i l l onwards i\.: to t u e n e x t r a i n s . B u r i n _ t n i s t i . . . t

tru: r i v e r 1L c l e a r b u t h a s a c o n s i d e r a b l e i - a t h o / e n l o a d

o i a p p r o x i m a t e l y 100 f a e c a l c o l i / 1 0 0 :.:1 (...:

xne s e n i o r w a t e r chemi s t on 4 . 5 . ' 0> ) •

f'i.e Aw ansa r i v e r v/hich i s t h e s i u ^ l e so arc:-; f o r t u e

.wausa Va l l ey o r o j e c t c a r r i e s \/ U . :li,_'.... - 1 . 1 . 1 I C d e S

dur ing , t h e rs . ' .ns *_nd no s i l t c u m ^ , t : .e d ry s e a s o n

( s e e ^ra^-ju ) . A l l y e s i a r c una i t h a s v e r y h i L h .

p a t h o g e n 1O:-..,JS a s was c e n s u r e d 'by b l s n t y r e . . a t e r Pcs rd

and the a u t . o r c i up to 2 0 , 0 0 0 iJ. c o l i / 1 0 0 nil.

- . 1 . Ww... .: eiW.o PKOAO/iAL

uBmnr ,:i Intern^*' ^ | Referanoe for Community V . Supply

!;..-t only i d c"ao;i oi' t h e iJoiHtxie r i v e r t r e a t m e n t wcr.•.::•. 1 .•• to r e d u c e t:,- patiiO jt-n l o e a .

.. s i c . s..,,.. i d i t e r op era. t i n , - a t a r a t e of 0 . 1 w./dw.. ;...iu

J. i l l ' j o v i v , -1... a:.

wi th. e f i l t ; i : i e d e e r t : ; o i l . 0 w. s n o u l o co - • u i i f o i c i ; t

eved r i v e r s s n a (wh ich snoui . - be; c l e u i . )

- l p -

At ?, d e s i g n flov: of 1>'0 ^pi-j a t o t a l l i l t e r a u r f a c e

area- should be r e . , j i r ^ : o i '•}&•) r--,'~. h i t h 1 tv:. tra­

i n t o r r. . a i i a b l o v/h^never a I ' l l t c r .xe :.-.i :.:• to be

r e;;. u i i e d.,

I" f C UO.1'6

. cifc>':(:r], J> t a n .en of 180 >n" each v i i . . a i a.'., t . txiir::ted c o s t o f K 1 0 0 , - o:-,y vi::;xe

a l c t „ j . of ]'. !>4,000 w i l l be r e q u i r e d t o c o n s t r u c t

t...t i i l t e r j ("cv'£.w s p o r t c o s t e x c l u d e ) .

, ' c a t r a n s p o r t c o s t e s t iwy .ee o.

c t i o n c o s t t h e t o t a l c o n e s to

c o n s t r u c t i o n c o s t

t r a n s p o r t c o s t

c o n t i n g e n c i e s e t c ,

TOTAL

o i t a e c o t i s i r u -

/ i i J u l '

27,000

1 0 , 0 0 0

y. ^ i ,ooo.-r i l t e r o p e r a t i o n

b i n c e slow sand i i l t r a t i o n i c new. i n t n a r u r a l

p i p e a w a t e r p r o j e c t s and t h e r e l o r e o p e r a t i o n a l

p r a c t i s e s a no r o u t i n e s Lave to n»_ > c v ; . I o ; c o ana

t r a i n e d to s t a f f i t i s v e r y i m p o r t a n t t o d e s i g n

a r o o n i t o r i n ^ r o u t i n e ay stein f o r tni.-. f i r s t p l a n t

f o r a t l e a s t 1 y e a r .

Tae r e s p o n s i b i l i t y f o r t r ie rnoui t o r i n < . p r o grain;;; e

s h o u l d I t unc e r trie d i r e c t r e s p o n s i b i l i t y of a

q u a l i f i e d e n g i n e e r , and t h e d a t a s h o u l d be con-1

d e n i e d i n t o a r e p o r t a t t h e end of t h e f i r s t y e a r .

a ' ' r , ;onitorin^; pro^raiame f o r slo>; t a n -

a t t a c h e d i n Appendix e

C o n s e v j e u t t o t h e m o n i t o r i n v ; .year a -

h e drawn up f o r t a e 11 a n t O p y r a x c r n ^

c o u r s e d e v e l o p e d f o r or . -e raa^rs

X .L J. L ' J I ^

tua l shou ld

; a t r a i n i n . .

l:\:i,n Jn .

To :..ahe :-',v:auza r i v e r w a t e r f i t f o r hu.:un consumpt ion

i s a r e a l c . a i i e n & e . ;<•<.•• an >; a r i v e r i s namely car...;, i n r

n i - j , f i i t l o a d s d u r i n g t h e r a i n s (helov? 5 cm v i s i b i -

lit . . , ' cep t i i ) a s i s i l l u s t r a t e c "oy Graph , and has

h i ^ n ^ a t h o ^ e n l o a d s c u r i a ;h-s va:ole , o a r . ( f e n Is'; L. .:. t :

Go^W'Ha > V L \

1.1

' 1 - •> ' -

••-' !

10

**•*+-* :••• \ : J

• * • ' * * ' • • • • ' • * • * ' ' f » * *

/ i \

/

/

/ L/

N 0 i ,v)

x • t » l » - » • > • . . • • ' t 1 I I 1 » I I I » I I . I I « I > • . I I < I » • I I I • I • I t . t • I

• D . - A KJ V is K y P e B r t ^ A R ^ 19

:.. L.-J. xj «•> . '• .JVH.'U

'..;,: u.

i';-.j..:.?.r

L- . J. . O.-.

, . C C i l CO T. V i t

/ 1 0 0 i::I

1 5 » 0 0 0 - l i . : , 0 0 0 ( H a i : 1 . > r f , .:;LG::.- .'.>oi.--rd) ' " " '• i 1**/" ' V ' , ' ^ *' ' ', , r n *i - , - \ ••• .— ' , i , - * - , • i

I)urin0 the 100^-10^3 L-ca.so:i t:.e t u i ^ i o i ty oio ;ict 2,0 b£j'0:ij ;.t vi s-.i b i i i ty b-?pir. of Je'>^ than 0- c::.- for - o r t th;>n a few cays be twee:: the end of January a'!;'": i-dd j.?ci;-A-uai'y. I;, addi t ion does the r i v e r c lea r f a i r ly ipiicJciy a f t e r r a i n , althou^n i s ;,;ay taive a couple of clays to reach a v i s i b i l i t y depth of lb err:. fa.:.ir^. into account tha t 1962-I9b'3 was a verj;. dry year , i t i s assumed that a normal year wi l l be a year v:ith hirn tu rb id i ty for a period of 3 n;onths, alt::ou._,ij tnere wil l be s p e l l s in between with lower t u r b i d i t i e s .

A t ea t ivi & /?eaeurin£ cyl inder to e s t ab l i sh the settle:.', en t c h a r a c t e r i s t i c s of the s i l t snov.ee tna t the s i l t has very much the saroe s e t t i i n ^ veloci ty as the raw water dim the Bwalla r i v e r , n.r.u-e.ly several v;ee:'.s to s e t t l e even a few cn.3.

A 2 phased treatment p lan t i s s u ^ t o t e d ae described under- ' -eco^iendation" .on ..p.ejie.s .14 and lb, •1'he l aase 1 wi l l cons is t of 2 p a r a l l e l , t anas , witn 1 XK\\I\ operating at trie t ime. During the r a ins each tan v v.ill l ive ly operate for per iods of a few days, however, t h i s should enable the opera&ors to clean tiie top b ens. of sand and r e f i l l i t , before the p a r a l l e l tank cuts i t s e l f ou t . Ine i-'na.ee two wi l l cons i s t of 3 tan:-,«, 2 of which o: erativ-^. a t the tirce, and a 5' rd one as a stand-by, to ta^e over whenever 1 ta:n< needs c lean in^ .

..-•.l. overa l l removal eff iciency of ?0,9 '/. of tbe patho-en load s.nouia be obtainea which should reduce the count iron; 20,000 to 20 or below. Tnis i s qu i t e acceptable .

In order to experiment with the above layout i t i s suj^ested to have- a treatment WOMB build a t V.ubalaliKa which wi l l serve a populat ion of 0;000 use r s . One p lant i s s i t ed and ready for cons t ruct ion now, during 1083. fhe f e a s i b i l i t y and e f f luen t qual i ty of the systeir! wi l l be'shown by th r s p l a n t , ouriuy the 1':/03-1 ?'-'•< rain;..1 season.

- 17 -

J i e i o r e t h e raw v.'ater. r e a d i e s t h e t r e a t m e n t p l a n t

i t ha s a l r e a d y p a s a e d tin-ova. r a ;;.;ri t t r a p vhaio..

reJiio^eb a l l b i a ^ e r sand p a r t i c l e e and a i i t „

A f t e r t n e t r e a t m e n t p l e a t e t I.uc;- 1 a XI .:.i ha,-, heen

i^aoe xo wora p r o p e r l y , v/illi t h e cora . t .vuet iov ' of t-'.':<

h a . i n a horlicli t i t a n a s t - t a r t , v^ic-h . - ixe h n - L-oei.

i c u a c a l r e a d y .

A . l f l j o u t f o r t h e Mar ina X a b o l i t i p l e a t i d shown i n

r ia^ranai-e y c

)i-LGKAahh 9 .-iAi-.IrJA AABOLITI LAYJ-OUT

PHv\i£ 4

hvices

ArhJO

f iacts

SiW

hand for the i i l t e r b e d s was found -within a disx; of 1^ r a l e s fron; the s i t e . .Appendix r i v e s ' ; a r i i c l e s ize D i s t r i b u t i o n .

- I'd -

; tr-iM.-: a C<i j . ^ a h 100/r/ K 12,000

£:.•.:;_...• C I j . ! ; , U J i . ; £_. L> ,'o^A-'

Xi ^UGVOi X ; ' , 0 ^ J

cchiiin^encies v;hich includes a Louse

aiiC a ience - f v.*--"^

T O T A L :'. 'i2,L0'":

^akina Xaboliti plant'

5 tanks a 200 ia a K 100/m K 100,000

sump of 50,000 £ 10,000

transport t:>,0.;0

contingencies including a house '^,C-J>-

and a fence

TOTAL K 200,000

Grand total for the i-.vanza Valley Treatr.jent I'iant

Y. 232,800.-

i-.ox'ii torin : 13ro;.:raruine • ^ • ^ - i i

I t i^ verj inj>ortant to establish a njonixorin^ pro0ra/.iu-e

ior the Kvanz-a Valley treatment voiJib r i ^ t fro;..- Xi.c f-.xa.rt,

The objectives should be

- t o asjesi the feasibility of the propose-:.: layout for

the i-lwanza vater

- t o deternine the filterrun leru. thj-. ci li.ase it.;..; 3 ~a^e •

2 over one lull year

- to ir.on.itcr tne effluent quality of > .iia.se 1 and i kase 2

(botn turbidity and pathogen load) over 1 full year

- tc record tne operational costs

- to develop xhe.operational routines and supervision

requirements for tnis treatr.ei;t plant in the staff

and to v.rite up a manual and training, pro£ra-V;::e.

A checklist and data record shee#t for the above prc- ra-...'..e

i s atxacheo in Appendix •

- 19 -

. Plh'AI 00;-;CLUSIOK

T"ne o b j e c t i v e of the exper iments c a r r i e d ou t with

the Zoinba- P i l o t p l a n t was to find a sui t a b l e m t u c c

of t r e a t m e n t fo r p o l l u t e d raw wa te r in r u r a l a r e a s

of Kalav.'i, which t r e a t m e n t p r o c e s s war- to he cheap

and s imple i n o p e r a t i o n , e a s i l y unders tood by the us

and ha rd ly t r a i n e d o p e r a t o r s , and which p roces s

can no t d e x e r i o r a t e the q u a l i t y of wa te r even under

very poor operaxfciiori.

The r e s u l t s of the exper imen t s i n d i c a t e t h a t a

p o s s i b l e s o l u t i o n to remove bcth t u r b i d i t y and

high pathogen l oads from rav. wa te r i s a 2 phased

slow sand f i l t r a t i o n p r c c e s s with Phase. 1 mainly

removing the s i l t l c a d and Phase, 2 xerricvin_ the

pathogen load f u r t h e r .

however, du r ing t h e r a i n y season t n i s t r e a t m e n t proc

w i l l " b e f a i r l y l a b o u r i n t e n s i v e because of the

r e g u l a r c l e a n i n g off of t h e accumulated s i l t froin

the f i l t e r s u r f a c e . hu t under a p r o p e r superv i sory

system' t n i s should be p o s s i b l e and q u i t e a l o t

loore a t t r a c t i v e than c o s t l y a l t e r n a t i v e s , both in

te r / 'S of Transpor t and chemical i n p u t s .

I - roposais for two p r o j e c t s , Dombole cno mvanza,

complete the r e p o r t , which p l a n t s snould hov, ever

be c a r e f u l l y monitored during the f i r s t i!ezr of

o p e r a t i o n to c o l l e c t t he i n f o r m a t i o n and t a x a t i o n a l

expe r i ence r equ i r ed to t r a i n o p e r a t o r s and w r i t e

an o p e r a t i o n a l Manual,

~Xo-

w . 'Pi 'fiCi-X 1

.*• r . i e r i-.ith a r ed polnte- : ' LC. IH. : ;\.

to ihc- 0 :>:ia.rk i s i n s e r t e d m i o \ . iv

v-'iit-ti- c r a v n from t h e s o u r c e iVJ <• b ^ . > o

i h e :upxh up to which u e r u l e r ca^

be inoi-z-tf-d Kith, t h e red 3iar\<: oa t h e

l u l e i s t i l l s een ir : t h e v i s i b i l i t y

d e p t n anci it? x-ecorded on a r e c o r d

s h e e t as a c a i i } ' reaoiri-v;.

Ta.-.en e v e r a f u l l s e a s o n t h i s ^ i v e s

an a c c u r a t e i d e a a c c u t t h e t u r b i d i t y

c f t h e w a t e r .

Tae t e s t can be d e n e lv\ u n s k i l l e d

p e r s o u e l .

Append ix 2 ;;i:;;ClifIG;:Ti.Ch^ Ox PARTICLi o l i r J o ' AJ-;Lf J'.-iJiJ-iUj.ii: DlJ'Mli;UTlOi\ Jr'UH KiViJ-K />Kii ihJ-.'iV ^ J . h ,.:., .USSD'IK THE iLCV. o;..-.;J

i-'l^'i'.-.:. «1 'i

j a r t i c l e ci ! (r:i:.j)

y • •

". • v. ~ c. . <f

1 •"" / "i '1

l . P - w . G . . . " N - >

w . _ • • * • . . - » . i J

o-11;-o.ov C.07

TCTAL

d 1 0 -

i 1 -LJ

s e

't'A'i-.bn PILOT PL/iVr I

r i v e r sano l e J i t

57

52 J

3C1>

4o

1 '-.

/o7

(:-) -JL

7 y: ~l

^ -'

•;_•

2

- • ' - • •

d:-j2lo " ~ T . '•• • '

1 •--

17, ,

C ' -''

c . ••'-•

L>:>

1 U l /

~ • • i" " "

<• i !

- i

7

^

' • ^ . t

c3

1 JO

0 . 0 7 i

0 . 3

irnur- r iver - ranc 1 £:-.:;• uniform;.

ffcirl 's Uiii'ic-r-.: and daji'.oo .'•.. <v_

nl^-jifiit ( - ra\; v:::ie:') (

ilovvi iij'uo '.! ,:a..-;e 1 >t.a:.,t 2

} rtK.yax-t: head lo?,3 over Phase 1 j - h a f j e 2

. '-ee.-.ly recce-din^:? ^but not i e ^ j r e c o r d i n g s .J. - ;;. c o i i count rav; v;<iier

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T:ie hwan^a r i v e r sand as excav&xec a t Jasichinc&i'.o acceptable for the i i l i e r b e d m a t e r i a l . The Kakoraa r i v e r sane: i s ne t uni fori!'; enough, in p a r t i c u l a r when top auo hotxorc sanci are niixe-'j up.

1 . L . HUlSh/U'v enc'i Y,-.ii. WOOD

Jlov, oand F i l t r a t i o n , W o r l d H e a l t h O r g a n i s a t i o n , 1 ?

2 . J . C . van DIJK and J .h ' .C. i - ; . 00=:^;

SIov Sand filtration for Co.w ,u:.i Zj -..ater :jupply

in ')evelopin^ Countries. A Design and Construction

Manual.

V;:0 International Reference Centre Technical 1- aper

AO 11 „

'i. , ; ^ ? i l Coa:^uniti- w a t e r S u p p l i e s

'..i.0 I n t e r n a t i o n a l R e f e r e n c e C e n t r e i t c A n i c a l } a n e r

.Ser ies So I B .

4.. A. PARAA;-SIVAI-J ana V.A. ililAlSALA.-ih

j J t s i a x ana C o n s t r u c t i o n ci ' Slow Sana x i l e e r s

i J r a i t R e p o r t I n t e r n a t i o n a l R e f e r e n c e C e n t r e .

t . 1..C. ThAiiH and -2.A.K. OUAKO

L o r i s o n t a l - f l o w C o a r s e - H a t e r i a l P r e f i l t i a t i o n

A s i a n I n s t i t u t e of Techno logy

R e s e a r c h R e p o r t Ko 7 0 .

NOTES ON FLOW CONTROL ARRANGEMENTS FOR SLOW SAND FILTRATION

. IHTROPUCTIOH

The twe write-upa which were dene cavers

- the treatment lay-eut and primelplee by H* ran Schaik

- the design fer the Kubalallka and Maklna Kabeliti tanke by B* Neakee*

The first write-up by H* van Schaik cavers the treatment arrangements

tw the Tery turbid and highly pelluted Mwanaa river water* The

reeeamendatiaae are based upen the eutceae ef experiments eenducted

ia Samba at the pilet treataent plant ever a peried ef 3 years*

Bewever, definite researoh with the Mwanaa water itself was aet dene*

Fer this reasen li^is iapertant that the Kubalallka treataent plant

is built eifcead ef the Hakina Kabeliti plant, the aala werks* The

[T Kubalalika plant sheuld be eperatieaal far 1 year te test the

appropriateness ef the suggested and prepesed treataent systea tw

,.£. the Mwanaa water*

The design by B* Menkes can be duild witheut tea away prebleas sinee

it is basically very siailar te the deaigas af the sterage tanks which

are built in the rural water supplies* Bewever,the flew central devices

regulating the supply and deaand aa wall as the centrals ever washing and

backfilling have aet been designed and theught eut carefully *

The inteatiea ef these netes is te give a. few auggastiens far the flew

oeatrel systea* In additiea X will try te find sane «drise in Methsvlands

an return tmr yen an this particular peiat*

2. TBEATMBJT FLAW AND CCMTBOL POIUTS

The prepesed treataent plant at Mwanaa cansists aft

- grit trap

- Phase 1 filter

- Phase 2 filter

m Eunp*

A lay aut af the plant ia drawn in Fig* 1*

-f~

r&-fc&T

< & -

plWM

wrQ* s o-S\W.

pHrtjcZ

The devices te eeatrel the flews will address tve mala issues:

1. the actual distributiea ef the water ever the individual tasks|

2* the matching ef supply and demaad.

2.1. DISTBIBUTIOH OVER THE PLANT

Te eaable preper eentrel erer the distributiea erer water erer the

eperatieaal tasks aad filters it is iBpertaat te hare eeatrel valves

iastalled at all braaohes ef beth islet aad eutlet lines, ef all the

tasks whieh are part ef the system*

The flew eeatrel valves sheuld be iastalled suoh that they are easily

eperatieaal aad clearly pesitieaed te prevent cenfusien*

9.2. THE MATCsHIQ OF SUPPLY AND DEMAND

The matching ef supply aad demaad is required at each stage ef the

plaat aad will therefere be discussed per each stages

- QUIT TRAP

The saeuat ef water passiag threugh the grit trap is equal te the

design flaw ef the inlet pipes sad is set meant te change at any

time.

Duriag the dry sessen, during times ef lew silt leads, the grit trap

caa fuactiea with clesed sceur plug, but duriag the rains the grit

trap caa be made self seeuriag by having the sceur p|>ug epen*

. PEASE 1 TANKS

The flew eateriag the Pahse 1 tank in eperatien is the design flew ef the

tap seetiea* Hewever, the flew precessed threugh the Phase 1 filter

sheuld be the demaad ef the users aad aet mere, sinoe any extra will

sherten the lifespan ef the eperatien*

Per this reasen it is suggested te have a ball valve oentrelliag the

eutflev ef the Phase 1 tank, which valve is leoated en the $elat ef

iaflew late the Phase 2 tank, and whieh cleses eff when the water level

ef the Phase 2 tank filter reaches its maximum height*

PHASE 2 TAKES

The inflew inte the Phase 2 tanks is equal te the tetal eutflew ef the

Phase 1 tanks, which eutflew is regulatee by the flew fleat valve en

the islet pipe late the tanks*

Phase 1 eeasists ef 2 tanks, witt enly 1 being in eperatien at any •>•

time mkk and wit the seoend tank either being cleaned er at stand by*

The distribntien ef the eutflev ef thane 1 tanks ever the 3 eperatienal

tanks ef Phase 2 is eeatrelled by water flew meters which shenld be

installed en the eutlet side ef the eperatienal Phase 2 filters, and

which shenld be read daily and flews shenld be calculated, in erder

te find the evenness in the distributien erer the eperatienal filters

ef the required flew, and preduotien.

The tetal prsduotien ef the eperatienal filters is regulated by a fleat

valve in the •nap

If the flews ef the eperatienal tanks were net as required, the flew

adjustacat can be aade by epening er elsing the oentrel valves en the

eutlet side ef the tanks a little thus increasing er decreasing the cut*

flew ef a partielnar falter aindng te balance the flews as per designed

eperatien.

Zt is suggested te hare the epening ef the fleat valve eeatrelled

inlet abeve the nrtsritskin nktalr n naxiinin water table thus allewing

fer sprinkling ef water late the tank at the entry aeaent which

will allew fer reaeratlea.

BEFILLIIIO OF TAM&B

After cleaning filter tanks sunt attna always be filled fren the batten

upwards te prevent air freo getting trapped in the sand pack/ This

filling can be dene very easily by allewing the aeutflew ef a parallel

tank te fill the just Cleaned tank up till just abeve the sand pack.

Thus clean water is used te fill frea the bet tea, which will net

affect the sand pack aaterial. The valves eeuld be temperarily arranged

such that the flew inte the next stage er Phase is stepped in erder te

fill up the parallel tank* filter.

Zt is ebvieus fren the sbeve peint that the levels ef the parallel tanks

must be set very accurately te enable this backfilling te happen.

I-

h. CLEAKIHQ OF TANKS/FILTERS

All filters should be eutfitted with a standpipe (epen) im the outlet

pipeline, vhieh reaches the top ef the tankvall (see diagramme 2)

I S&ttjWfc

» . • •

TE"

2 " Jtffl-Pte

The level ef water la this stand pipes sheuld be measured daily bjt the plant

eperater with a dip stick which has a red nark en it indicating the minimum

water level which is the lvelel at which the filter bed sheuld be eleaned

bj removing the tep 5 en. ef the sand pack*

The dip stick measurements Bust be taken daily and reeerded an a reeerd sheet

far inspection by the engineer in charge* ,

When a filter needs cleaning, the supernatant water is allowed to drain away.

The drain paints are seenr paints in the eutlet lines just beyend the eentrel

valves and the stand pipes ef the tanks*( see diagramme 5)*

As seen as the water level has dropped te seme en* below the filterbed surface

cleaning can be started* It is very important net te allew the filter te be

drained completely, since the refilling volume and time will be lengthened

linearly*

3

H 1 ^ f t " l ' "J *

N

rm W

• • > ! ® ioox |toi"#*r

5 # VALVE NUMBERING AMD OPERATIONAL INSTRUCTIONS

/•i.

It is very important to work out a good valve number system which sheuld be

used consequently te design the operational instructions for the different

operations/Mich as changing over from Filter 1 te Filter 2 in Phase .1, _,

) \

k

the valve eperatiens te clean er refill a filter etc0

The eperatienal instructiens sheuld be in shert and clear fennat for

a minimum trained ftperatoi".

CLEANING 0? SAND

Th« cleaning of the sand frem the Phase 1 filterbeds can be dene en site

in a small cleaning tank using the clean eatflew frem the Phase 1 filters*

The cleaning tank ceuld be sited within the drain gully fresa the Jiletre.

The sand can be cleaned by agitatien with a shevel er ether teel, and can

be breught back ente the filter immediately afterwards*

Phase 2 sand sheuld net be breught back immediately afterwards, which

is accerding te the literature en this bad practise because it will destrey

the bielegical tep layer ef the filterbed, thus reducing the romeval

efficiency.

Phase 2 filters sheuld be,cleaned until the re sanding level is reached,

which sheuld be set at abeut i n sand pack remaining* When this level is reached

all sand sheuld be remeved and the sand pack replaced with clean sand*

7. EXAMPLE OPERATIONAL INSTRUCTION:

Refilling ef lilter A Phase 2*

Lay eut ef plant and valves:

v\w$zx

Assuming that Filters B and C are eperatieaal the refilliag frem the

bettea is dene with effluent water frea Filetrs B and C.

Clese ValTe S-1 .

Open yalre A 2

Allew the water te eater A up till level ef water is abeve the sandlevel.

Close A 2 and •pen e 1 agaia.

Operatiea completed©

' - • - • • i

H.P.J. vaa Schaik j

SESIOR WATER BtGINEER