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Wat. Res. Vol. 24, No. 6, pp. 717-723, 1990 0043-1354/90 $3,00 + 0.00
Printed in Great Britain. All rights reserved Copyright © 1990 PergamonPress plc
A L A B O R A T O R Y S C A L E M O D E L F O R E V A L U A T I N G
E F F L U E N T T O X I C IT Y IN A C T IV A T E D S L U D G E
W A S T E W A T E R T R E A T M E N T P L A N T S
DONALD J. VERSTEEG* and DANIEL M. WOLTERING
Environmental Safety Department, The Procter & Gamble Company, Ivorydale Technical Center,
Cincinnati, OH 45217, U.S.A.
First received M ay 1989; accepted in revised orm December 1 989)
Abstract--Laboratory-scale wastewater treatment systems were used to assess the potential contribution
of a specific waste source, a detergent manufacturing plant, to wastewater treatment plant (WWTP)
effluent toxicity. Laboratory-scale, continuously-fed activated sludge treatment systems (CAS units) were
established and seeded with sludge from one of two activated sludge WWTPs. The CAS units were fed
influent from these WWTPs supplemented with detergent manufacturing plant waste (plant waste). CAS
unit effluent toxicity was measured with the 7 day
Ceriodaphnia dubia
survival and reproduction test and
the 4 day Selenastrum capricornutum population growth test. Control (ambient W~VTP nfluent) CAS unit
and actual WWTP effluentshad similar toxicity, indicating the CAS units generated effluent oxicologically
similar to actual effluent for the two species tested. Untreated WWTP influent was supplemented with
atypically high concentrations of plant waste in an attempt to establish a dose--response relationship
between influent plant waste levels and effluent toxicity. However, there was no trend toward increasing
effluent toxicity to Ceriodaphnia or algae with increasing influent plant waste concentrations. Thus, the
detergent manufacturing plant waste is not contributing to the toxicity of the municipal WWTP effluent.
This case study demonstrated the utility of CAS units for assessing the impact of WWTP influent sources
on final effluent toxicity.
Key words--wastewater treatment, effluent toxicity, algae, invertebrates, Ceriodaphnia, surfactants,
manufacturing plant
INTRODUCTION
The U.S. Envir onment al Protection Agency water
quality based toxics control strategy promotes the
utilization of toxicity data on single species to assess
and control the discharge of toxic substances into
receiving waters (U.S. EPA, 1985). Whole effluent
toxicity tests with the daphnid, Ceriodaphnia dubia,
a green algae, Se lenas t rum capr icornuturn and the
fathead minnow, P i m e p h a l e s p r o m e l a s , are recom-
mended to assess potential chronic effluent impacts
on in-stream communities (Horning and Weber,
1985).
Municipal wastewater treatment plant (WWTP)
effluents have been observed to be acutely an d chron-
ically toxic to aquatic organisms, with up to 79% of
effluents reported to be acutely toxic to aquatic life
(Tebo, 1986; Neiheisel et al . , 1988). Effluents exceed-
ing permitted toxicity limits may be required to
reduce effluent toxicity. Effluent toxicity reduction
can be accomplished through a toxicity identification
and reduction evaluation (TI/RE) in which toxicants
are identified and toxicity is ameliorated by aug-
mented treatment processes and programs designed
to restrict sources of toxic compounds (Mount and
Anderson-Carnahan, 1988), At municipal WWTPs,
*Author to whom all correspondence should be addressed.
the TI/RE process may involve going up the pipe
to identify industrial or commercial sources of toxic-
ity (U.S. EPA Science Advisory Board, 1988). But,
how should toxicity info rmati on on untreat ed waste
be obtained and interpreted to accurately reflect
toxicity in the final treated effluent? Toxicity tests on
untr eated wastes may no t accurately assess the contr i-
bution of a waste to final effluent toxicity, especially
in waste streams containi ng compound s removed by
treatment processes. Knowledge of total waste
treatability (e.g. BOD removal) might not always be
useful as effluent levels of residual toxic compounds
will not be known. The key parameter to understa nd
is the quan tity of final effluent toxicity a specific waste
source contains. In this study, model waste treatment
systems were used to assess the con tribut ion of a
detergent manufac turin g plant waste to final effluent
toxicity. This approach has been used successfully to
evaluate the effect of treatment on the toxicity of a
number of compounds (Horning
et a l . ,
1984; Botts
e t
al. , 1989).
Predicting the potentia l contribu tion of the manu-
facturing plant waste to WWTP effluent toxicity is
complicated by: (1) the chemical complexity of the
manu fac tur ing plan t waste; (2) the differential
WWTP removal of manuf actur ing plant waste com-
ponents; and (3) the potential for toxicological inter-
actions among components of the final WWTP
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718
INFLUENT/SLUDGE
SOURCE
D O N A LD J V ER S TEEG a n d D A N IEL M W O LTER IN G
W W T L , - - - J I
; , N . L U E . .A O . L U O O E I [ ' . F L U ' A . O S ' U O 0 '
MANUFACTURING
PLANTASTE
DOSING
~_~ Mnnufacturlng
Plant aste
4X
C A S U N I T S ~ ~ ~ ~ ~ ~
TOXICITY
TESTS
EFFLUENT EFFLUENT EFFLUENT EFFLUENT EFFLUENT EFFLUENT
Fig . 1 . F low d iagram of the exper imenta l des ign demons tra t ing the source o f s ludge and in f luen t , the
add i t ion o f m anufac tu r ing p lan t was tes and the use o f CAS un i t e ffluen ts fo r tox ic i ty te st ing .
e f f lu e n t . T o c o n d u c t t h e m o s t r e l e v a n t t e s t i n g p o s s-
i b l e, w e r e a s o n e d t h a t e f f lu e n t t o x i c i t y s h o u l d b e
a s s es s e d f o l l o w i n g a c t u a l o r s i m u l a t e d w a s t e w a t e r
t r e a t m e n t o f th e m a n u f a c t u r i n g p l a n t w a s t e .
T h i s r e s e a r c h h a d t w o p u r p o s e s . F i r s t , t o a s se s s t h e
f e a s i b il i t y o f c o u p l i n g a l a b o r a t o r y - s c a l e w a s t e t r e a t -
m e n t s y s t e m w i t h e f f l u e n t c h r o n i c t o x i c i t y a s s a y s t o
d e t e r m i n e t h e c o n t r i b u t i o n o f a n i n f l u e n t s o u r c e t o
f i n a l W W T P e f f lu e n t t o x i c it y . T h i s r e s e a r c h w a s
c o n d u c t e d u s i n g a d e t e rg e n t m a n u f a c t u r i n g p l a n t
w a s t e a s a ca s e s t u d y . T h e m a n u f a c t u r i n g p l a n t
r e l e a s e s w a s t e s a l o n g w i t h o t h e r d o m e s t i c , c o m m e r -
c i a l a n d i n d u s t r i a l s o u r c e s to a m u n i c i p a l W W T P .
E f f lu e n t f r o m t h e m u n i c i p a l W W T P w a s o b s e r v e d to
b e t o x i c t o a q u a t i c l i f e a n d t h e i ss u e w a s t h e l e v el o f
f i n al e ff l u e nt to x i c i t y c o n t r i b u t e d b y t h e m a n u f a c t u r -
i n g p l a n t. T h e s e c o n d o b j e c t i v e o f t h is s t u d y w a s t o
d e t e r m i n e , u n d e r a r e a l i s t i c w o r s t c a s e s c e n a r i o , i . e . a
W W T P r e c ei v in g b o t h d o m e s t i c w a s te a n d d e t e r g en t
m a n u f a c t u r i n g p l a n t w a s t e , w h e t h e r s u r f a c t a n t s , t h e
m a j o r c o m p o n e n t s o f t h e m a n u f a c t u r i n g p l a n t w a s te ,
a r e li k e l y t o c o n t r i b u t e t o m u n i c i p a l W W T P e f f lu e n t
t o x i c i t y .
MATERIALS AND METHODS
Wastewater sources
Two was tewate r t rea tment p lan t s ludges and in f luen t
sources (A and B) were used to es tab l ish and opera te s ix
CAS (con t inuous ly -fed ac t iva ted s ludge) un i ts . WWTP A is
an appro x . 20 mil l ion ga l lons pe r day conven t io na l ac t iva ted
s ludge t rea tm ent p lan t rece iv ing was te f rom dom es t ic (90 )
and indus tr ia l (10 ) sources . The indus tr ia l inpu t includes
w a s te s f ro m th e d e te rg e n t m a n u fa c tu r in g p l a n t . WWT P B
is a 1 mil l ion ga l lon pe r day , ex tended ae ra t ion ac t iva ted
s ludge p lan t rece iving w as tes en t i re ly f rom dom es t ic sources .
C S units
T h re e C A S u n i t s w e re se ed e d w i th s lu d g e f ro m W W T P A
(Fig . I ) . One un i t was opera ted with WW TP A in flUent on ly .
This in f luen t con ta ins ambien t leve ls o f the de te rgen t m anu-
fac tu r ing p lan t was te . In f luen t to the o the r two CAS un i ts
w e re s p ik ed w i th a d d i t io n a l d e t e rg e n t m a n u fa c tu r in g p l a n t
was te a t 4 and 16 t imes the typ ica l level o f p lan t was te in
WWTP A in f luen t (F ig . 1 ) . Three CAS un i ts were se t up
w i t h s l u d g e f r o m W W T P B a n d o p e r a t e d w i t h W W T P B
inf luen t . One un i t was opera ted with un trea ted in f luen t
a lone ( i .e . normal load in g o f domes t ic was te and n o de te r-
gen t manufac tu r ing p lan t was te ) . In f luen t to the o the r two
uni ts were sp iked with 4 an d 16 t imes the p lan t was te leve ls
in W W TP A influent (Fig. 1).
Each labora to ry-sca le CAS un i t cons is ted o f a p lex ig las
aeration basin and a 21. cylindrical c larifier (Fig. 2). The
aera t ion bas in con ta ined 61 . o f ac t iva ted sludge d ispe rsed by
two ae ra t ion tubes . The ae ra t ion bas in d ischarged th rough
an ov erf low tube in to a c la r i f ie r s ti r red by a sha f t m ixer . The
Pump
Influsn
Plus
PlantWaste
4o c )
Compressed
Air ~
Aeration
Section
/
Effluent
Pump
Waste
Solids ecycle
Pump
Fig . 2 . Schematic d iagram of the CAS un i ts used in the
trea tment o f the in f luen t and th~ was te f rom a de te rgen t
m a n u fa c tu r in g p l a n t .
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W a s t e c o n t r i b u t i o n t o e f f l u e n t t o x i c i ty
719
c l a r if i e r h a d a r e cy c le d i s c h a r g e t u b e i n t h e b o t t o m a n d a n
over f low fo r e f f luen t d i scharge . S ludge se t t l ing in the c la r i f i e r
w a s p e r i o d i c a l l y re c y c le d (1 5 m i n p e r h ) t o t h e a e r a t i o n b a s i n
b y a p e r i s t a l t ic p u m p . E f f l u e n t f ro m t h e c l a r i f ie r w a s c o r n -
p o s i t e d i n a 2 0 1 . p o l y p r o p y l e n e p a i l f o r t o x i c o l o g i c a l a n d
a n a l y t i c a l s a m p l i n g .
G r a b s a m p l e s o f W W T P i n f t u e n t s w e r e c o l l e c te d tw i c e
w e e k l y , t r a n s p o r t e d t o t h e l a b o r a t o r y a n d s t o r e d i n
p o l y p r o p y l e n e c o n t a i n e r s a t 4 °C . S a m p l e s w e r e f e d i n t o
C A S u n i t s i m m e d i a t e l y u p o n r e c e ip t a t t h e l a b o r a t o r y . D u e
t o t h e i n f l u e n t f e e d ra t e , a p o r t i o n o f i n f l u e n t s a m p l e s w e r e
4 d a y s o l d w h e n t r e a t e d . I n f l u e n t w a s f e d b y p e r i s t a l t ic
p u m p t o t h e C A S u n i t s a t a m e a n f lo w r a t e o f 1 6 .6 m l / m i n .
O p e r a t i o n a l p a r a m e t e r s i n t h e C A S u n i t s w e r e d e s ig n e d t o
b e s i m i l a r t o a c t u a l c o n v e n t i o n a l w a s t e w a t e r t r e a t m e n t
p l a n t s ( T a b l e 1 ) ( M e t c a l f & E d d y , 1 9 79 ; N a m k u n g a n d
R i t t m a n n , 1 9 8 7 ) . W a s t i n g o f s l u d g e w a s c a r r i e d o u t a s
n e e d e d t o m a i n t a i n t h e m i x e d l i q u o r s u s p e n d e d s o l i d s
( M L S S ) l i m i t s . I n fl u e n t , e ff l u e nt a n d m i x e d l i q u o r t o t a l
s u s p e n d e d s o l i d s , a n d i n f l u e n t a n d e ff l u e n t p H a n d t o t a l
o r g a n i c c a r b o n w e r e r o u t i n e ly m o n i t o r e d d u r i n g t h e d o s i n g
p e r i o d .
I n i ti a l ly , C A S u n i t s w e r e o p e r a t e d f o r 1 4 d a y s w i t h
u n t r e a t e d i n f l u e n t o n l y . T h i s p r e d o s e p e r i o d a l l o w e d t h e
C A S u n i t s t o r e a c h a s t a t e o f e q u i l i b r i u m b e f o r e d o s i n g w i t h
p l a n t w a s t e . A f t e r t h e p r e d o s e p e r i o d , i n f l u e n t s w e re s u p p l e -
m e n t e d w i t h d e t e r g e n t m a n u f a c t u r i n g p l a n t w a s t e t o a p -
p r o x i m a t e i n c r e a s e s o f z e r o ( a m b i e n t i n f l u e n t ) , 4 a n d 1 6
t i m e s th e l e ve l o f m a n u f a c t u r i n g p l a n t w a s t e i n W W T P A
i n f l u e n t . T h e e x a g g e r a t e d d o s e s o f p l a n t w a s t e s w e r e i n -
t e n d e d t o g e n e r a t e e f f lu e n t s f o r t o x i c it y t e s t i n g w h i c h c o u l d
b e c o m p a r e d i n a d o s e -r e l a te d m a n n e r . O b s e r v a t i o n o f a
d o s e - r e s p o n s e r e l a ti o n s h i p b e tw e e n t h e c o n c e n t r a t i o n o f t h e
m a n u f a c t u r i n g p l a n t w a s t e a n d e f f l u e n t t o x i c i t y w o u l d b e
s u b s t a n t i a l e v i d e n c e o f a c a u s e a n d e f f ec t r e l a t i o n s h i p . T h e
d o s i n g p e r i o d l a s t e d f o r 3 2 d a y s a l l o w i n g s u f f i c ie n t ti m e f o r
a c c l i m a t i o n o f t h e a c t i v a t e d s l u d g e m i c r o b i a l c o m m u n i t i e s
t o p l a n t w a s t e u n d e r l a b o r a t o r y c o n d i t i o n s . C o n t r o l C A S
u n i t e f f lu e n t s am p l e s w e r e c o l l e ct e d f o r a c u t e t o x i c i t y t e s t i n g
d u r i n g t h e e n t i r e d o s i n g p e r i o d . E f f l u e nt s a m p l e s f o r c h r o n i c
t o x i c i t y te s t i n g w e r e c o ll e c t e d d u r i n g t h e l a s t 7 d a y s o f t h e
d o s i n g p e r i o d .
T o x i c i t y t e s t s
C o n t r o l C A S u n i t i n f l u e n t s a n d e f f lu e n t s w e r e t e s t e d f o r
a c u t e t o x i c it y t o Cer i o d a p h n i a d u b i a b y t h e m e t h o d o f P e l ti e r
a n d W e b e r ( 1 9 8 5 ) . G r a b s a m p l e s o f i n f l u e n t a n d 2 4 h
c o m p o s i t e s a m p l e s o f e f f l u e n t w e r e u s e d . T o x i c i t y t e s t s w e re
i n i t i a t e d i m m e d i a t e l y a f t e r s a m p l i n g a n d t e s t s a m p l e s w e r e
c h a n g e d a f t e r 2 4 h w i t h a f r e s h g r a b s a m p l e o f i n f l u e n t a n d
a secon d 24-h comp os i te o f e f fluen t . Th ese t e s t s were
c o n d u c t e d t o d e t e r m i n e t h e v a r i a b i l i t y i n i n f l u e n t t o x ic i t y
a n d t h e a b i l i t y o f C A S u n i t s t o r e m o v e t o x i c i t y ,
E f f lu e n t s h o r t - t e r m c h r o n i c t o x i c it y t e s ts w i t h
C e r i o d a p h -
nia dubia
a n d
S e l en a s t ru m ca p r i co rn u t u rn
were used to assess
t h e c h r o n i c t o x i c i t y o f C A S e f f lu e n t s a n d f i n a l e ff l u en t s f ro m
W W T P s A a n d B . C e r i o d a p h n i a w e r e c h o s e n d u e t o t h e i r
g e n e r a l l y g r e a t e r s e n s i t i v it y t h a n f i sh t o W W T P e f f lu e n t s
( d a t a n o t s h o w n ) . S e l e n a s t r u m w a s s e l e c te d d u e t o t h e
s e n s i t iv i t y o f a l g a e t o s u r f a c t a n t s , t h e s h o r t d u r a t i o n o f
t o x i c i t y t e s t s w i t h a l g a e , a n d t h e i r c r i t i c a l p o s i t i o n i n t h e
e c o s y s t e m . T h e s e t e s t s w e r e c o n d u c t e d a c c o r d i n g t o t h e
Table 1. Operational conditions of the CAS units
Parameter
Aeration tank volume (litres) 6.0
Aeration rate (l/min) 6.0
Wastew ater flow (I/d) 23.9
Hydraulic retention time (h) 6.0
Sludge retention time (d) 12.0
Mixed l iquor suspended so lids MLS S (m g / l ) 200 0-3 000
Sludge volume inde x SVI (ml/I) < 100
m e t h o d s o f H o r n i n g a n d W e b e r ( 1 9 8 5 ) w i t h t h e e x c e p ti o n
t h a t C e r i o d a p h n i a w e r e c u l t u r e d a n d t e s t e d i n i n d i v i d u a l
30 ml p las t i c cups f i l l ed wi th 20 ml o f t e s t so lu t ion . F i l t e red
L i t t l e M i a m i r i v e r w a t e r, a r e l a ti v e l y c l e a n s o u r c e o f n a t u r a l
d i l u t i o n w a t e r , w a s c o l l ec t e d a t X e n i a , O h i o a n d u s e d f o r
C e r i o d a p h n i a a n d S e l e n a s tr u m c u l t u r e a n d a s d i l u t i o n w a t e r
i n t o x i c it y t e st s . D u r i n g C e r i o d a p h n i a 7 d a y c h r o n i c t o x i c it y
t e s t s , d a i l y 2 4 - h c o m p o s i t e d s a m p l e s f r o m e a c h C A S u n i t
e f f lu e n t w e r e u s e d t o m a k e t h e d a i l y r e n e w a l s o f t e s t
s o l u t i o n s . O b s e r v a t i o n s o n t h e s u r v i v a l a n d r e p r o d u c t i o n o f
C e r i o d a p h n i a w e r e m a d e d a i l y a t t h e t i m e o f t r a n s f e r .
T h e 4 d a y a l g a l t e s t s w e r e r u n c o n c u r r e n t l y w i t h t h e
C e r i o d a p h n i a t o x i c i t y t e s ts . T e s t s o l u t i o n s w e r e n o t r e n e w e d
d u r i n g t h e te s t . A l g a e w e r e i n c u b a t e d a t 2 4°C a n d 8 6 E s - 1
m - 2 ( e q u i v a l e n t t o 4 0 0 f t - c c o o l w h i t e f l u o r e s c e n t l i g h t) o n
a s h a k e r t a b l e o s c i l l a t i n g a t 1 0 0 r p m . A f t e r 4 d a y s o f
i n c u b a t i o n , p o p u l a t i o n g r o w t h w a s a s s e s s e d b y q u a n t i f y i n g
a l g a l b i o m a s s ( c h l o r o p h y l l a ) f l u o r o m e t r i c a l l y o n a T u r n e r
m o d e l 1 11 f l u o r o m e t e r ( A P H A , 1 9 85 ).
A n a l y t i c a l
S u r f a c t a n t a n a l y t i c a l s a m p l e s w e r e 2 4 h c o m p o s i t e s o f
C A S e f f l u e n t s . S a m p l e s c o l l e c t e d f o r a n i o n i c a n d n o n i o n i c
s u r f a c t a n t a n a l y s e s w e r e p r e s e r v e d w i t h 1 % f o r m a l i n a n d
s t o r e d a t 4 °C . S a m p l e s c o l l e c t e d f o r c a t i o n i c s u r f a c t a n t
a n a l y s e s w e re p r e s e r v e d w i t h 1 % f o r m a l i n a n d 5 m g / l o f
alkyl ethoxylate (C14_15A E 7 ), a n d s t o r e d a t 4 °C . T h e s a m p l e s
w e r e a n a l y z e d f o r t o t a l n o n i o n i c s u r f a c t a n t s b y a m o d i f ic a -
t i o n o f t h e c o b a l t t h i o c y a n a t e a c t i v e s u b s t a n c e m e t h o d
( A P H A , 1 9 8 5 ) , l i n e a r a l k y l b e n z e n e s u l f o n a t e s ( L A S ) b y
d e s u l f o n a t i o n g a s c h r o m a t o g r a p h y ( O s b o r n e , 1 9 86 ), a n d t h e
f o l l o w i n g c a t i o n i c s u r f a c t a n t s b y a m o d i f i c a t i o n o f t h e
m e t h o d o f W e e ( 19 8 4) ; d i t a l l o w d i m e t h y l a m m o n i u m c h l o -
r id e , m o n o t a l l o w t r i m e t h y l a m m o n i u m c h l o r i d e a n d d o d e -
c yl t ri m e t h y l a m m o n i u m c h l o r i d e . N o t e t h a t t h e a n a l y t ic a l
m e t h o d f o r t h e n o n i o n i e s u r f a c t a n t s i s a n o n s p e c if i c c o l o r i-
m e t r i c m e t h o d r e p o r te d t o o v e r e s t i m a t e t h e c o n c e n t r a ti o n o f
n o n i o n i c s u r f a c t a n t i n W W T P e f f l u e n t s ( G l e d h i l l et a l .
1 9 89 ). T h u s , r e s u l ts o f n o n i o n i c s u r f a c t a n t a n a l y s e s a r e
r e p o r t e d i n g e n e r a l t e r m s o n l y .
W a t e r q u a l i t y p a r a m e t e r s i n c l u d i n g h a r d n e s s , a lk a l i n i t y ,
d i s s o l v e d o x y g e n , t o t a l o r g a n i c c a r b o n , t o t a l s u s p e n d e d
s o l i d s , a m m o n i a , c o n d u c t i v i t y a n d p H w e r e m e a s u r e d i n
d i l u t i o n w a t e r a n d C A S i n f l u e n t a n d e f f l u e n t b y a c c e p t e d
m e t h o d s ( A P H A , 1 9 85 ). C A S u n i t s l u d g e v o l u m e in d e x
( S V I ) w a s m e a s u r e d a c c o r d i n g t o A P H A ( 1 9 8 5 ) u s i n g a
3 0 m i n s e t t l i n g ti m e . W a t e r q u a l i t y p a r a m e t e r s w e r e m e a -
s u r e d a t t h e b e g i n n i n g o f t h e a l g a l t e s t a n d d a i l y d u r i n g
C e r i o d a p h n i a t e s t i n g .
S t a t i s t i c s
S u r v i v a l d a t a w e r e a n a l y z e d b y t h e m e t h o d s d e s c r i b e d i n
P e l t i e r a n d W e b e r ( 1 9 8 5 ) . C e r i o d a p h n i a y o u n g p r o d u c t i o n
a n d a l ga l p o p u l a t i o n g r o w t h d a t a w e r e a n al y z e d b y n o n l i n -
ea r mul t ip le regress ion ana lys i s on SAS (SAS, 1986) .
T o x i c i t y t e s t r e s u l t s a r e s u m m a r i z e d i n t h i s s t u d y a s t h e
e f fe c t iv e c o n c e n t r a t i o n o f e f f lu e n t r e d u c i n g b i o l o g i c a l re -
s p o n s e , s u r v i v a l o r r e p r o d u c t i o n , b y 5 0 % ( E Cs 0 v a l u e s ) w i t h
95% conf idence in te rva l s . The ECs0 s ta t i s t i c was se lec ted to
iden t i fy e f f luen t concen t ra t ions caus ing a spec i f i c l eve l o f
t o x i c i t y a n d d o e s n o t i n d i c a t e a t o x i c i t y t h r e s h o l d o r
b i o l o g i c a l r el e v a n c e i n t h e r e c e i v i n g e n v i r o n m e n t . I n u s i n g
n o o b s e r v e d e f f ec t ( N O E C ) a n d f i r st o b s e r v e d e f fe c t c o n c e n -
t r a t i o n s ( F O E C ) , b i o l o g i c a l e f f e c t s v a r i e d g r e a t l y a m o n g
C A S u n i t t r ea t m e n t s w i t h s i m i la r N O E C s a n d F O E C s .
O t h e r s h a v e o b s e r v e d t h i s e f f e c t a n d r e c o m m e n d t h e u s e o f
a d o s e - r e s p o n s e s t a t i s ti c a l a p p r o a c h i n p l a ce o f t h e h y p o t h -
e s is t e s t i n g a p p r o a c h ( K r u m p , 1 9 84 ; B a r n t h o u s e e t a l .
1 98 7) . T h u s , t o m a k e m e a n i n g f u l c o m p a r i s o n s a m o n g C A S
u n i t t r e a t m e n t s i n t h i s s t u d y , b i o l o g i c a l e f f e c t s w e r e h e l d
c o n s t a n t a t 5 0 % .
F o r C e r i o d a p h n i a c h r o n i c t e s t s , E C s 0 v a l u e s w e r e c a lc u -
l a t e d b a s e d o n s u r v iv a l a n d y o u n g p r o d u c t i o n . T h e l o w e r o f
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7 2 0 D O N A L D J . V E R ST E EG a n d D A N I E L M . W O L T E R I N G
T a b l e 2 . C o n c e n t r a t i o n [ m e a n ( m g / l ); ( S D ) ; n = 4 ] o f s u r f a c t a n t s * i n C A S u n i t s a n d a c t u a l W W T P e f f lu e n ts
T r ea tm e n t s ys te m D T D M A C M T T M A C C I : T M A C L A S
W as t e wat e r t r e a t m e n t p l an t s
W W T P A e f fl u en t ( n = 7 ) 0 . 0 38 ( 0 .0 1 8) < 0 . 0 1 2 t < 0 . 0 1 0 t < 0 . 0 5 0 t
W W T P B e f f l u e n t ( n = 3 ) 0 . 0 2 5 ( 0 . 0 2 7 ) < 0 .0 0 5 I < 0 . 0 0 5 t 0 . 1 3 0 t
C S u n it s
W W T P A c o n t r o l 0 . 7 6 0 ( 0 .3 9 ) 0 . 0 0 9 ( 0 . 00 2 ) < 0 . 0 0 5 t 0 . 0 7 0 ( 0 . 03 2 )
W W T P A 4 × p l a n t w a s t e 4 . 5 3 (0 . 8 4 ) 0 . 0 0 8 (0 . 0 0 3 ) < 0 . 0 0 5 t 0 . 3 9 0( 0 . 04 2 )
W W T P A 1 6 x p l a n t w a s t e 2 0 .3 ( 4 .5 7 ) 0 . 0 2 4 ( 0 . 00 1 ) < 0 . 0 0 5 t 3 . 10 ( 1 . 4 6 )
W W T P B c o n t r o l 0 . 5 5 0 ( 0 .2 8 ) 0 . 0 1 0 ( 0 . 00 5 ) < 0 . 0 0 5 t 0 . 1 4 0 ( 0 . 01 0 )
W W T P B + 4 x p l a n t w a s t e 2 . 9 8 ( 1 . 4 1 ) 0 . 0 1 1 ( 0 . 0 0 5 ) 1 0 0 % , b u t w a s g e n e r a l l y l es s t o x i c th a n W W T P
i n f l u e n t B ( T a b l e 3 ). W W T P B i n fi u e n t w a s c o n s i s -
t e n t l y a c u t e l y t o x i c t o C e r i o d a p h n i a ; L C s 0 v a l u e s
w e r e l es s t h a n 5 0 % . E f f lu e n t s fr o m c o n t r o l C A S u n i t s
w e r e c o n s i s t e n t ly o f l o w a c u t e t o x i c i t y i n d i c a t i n g
C A S u n i t s e f fe c ti v e ly r e m o v e d a c u t e l y to x i c c o m p o -
n e n t s . M o r e s e n si t iv e c h r o n i c e n d p o i n t s , t h o u g h ,
w e r e n e e d e d t o d i s t i n g u i s h e f fl u en t t o x i c i t y a m o n g
C A S u n i t s .
C h r o n i c t o x i c i t y
T o x i c i t ie s o f W W T P A a n d B e ff lu e n ts w e r e s i m i l a r
t o C e r i o d a p h n i a ( T a b l e 4 ) . E C 50 c o n c e n t r a t i o n s w e r e
2 4 a n d 2 2 °/ '0 e f f lu e n t in W W T P A a n d B , r e s p e c t i v e l y .
C o n t r o l C A S u n i t a n d a c t u a l e f f l u e n t s a l s o h a d
s i m i l a r t o x i ci t ie s . F o r W W T P A , c h r o n i c E C s 0 c o n -
c e n t r a t i o n s w e r e 2 4 % i n t h e a c t u a l W W T P e f f l u e n t
a n d 3 3 % i n t h e c o n t r o l C A S u n i t e f f l u e n t t o C e r i o -
d a p h n i a . F o r W W T P B , e ff lu e n t E C s 0 c o n c e n t r a t i o n s
w e r e 2 2 a n d 1 6 % i n th e a c t u a l W W T P a n d c o n t r o l
C A S u n i t e f f l u e n t s , r e s p e c t i v e l y .
I n W W T P A C A S u n i t s , C e r io d a p h n i a c h ro n i c
e f fl u e n t E C s0 c o n c e n t r a t i o n s w e r e 3 3 % f o r t h e c o n t r o l
C A S u n i t , 4 6 % f o r th e C A S u n i t re c e i v in g 4 x p l a n t
w a s t e a n d 1 3 % f o r t h e 1 6 x p l a n t w a s t e C A S u n i t
( T a b l e 4 ) . I n W W T P B C A S u n i t s , c h r o n i c e f f l u e n t
C e r i o d a p h n i a E Cs 0 c o n c e n t r a t i o n s w e r e 1 6 % f o r t h e
c o n t r o l C A S u n i t , 3 5 % f o r t h e C A S u n i t r e c e i v i n g
T a b l e 3 . T h e a c u t e t o x i c i ty o f i n f lu e n t s a n d e f f l u e nt s f r o m c o n t r o l C A S u n i t s t o Ce r i odaphn i a dub i a
4 8 - h L C s 0 v a l u e ( % )
S a m p l e t y p e W e e k : 1 2 3 4 5
W W T P A c o n t r o l
i n f l u e n t 2 2 . 2 > 5 0 > 1 0 0 > 1 0 0 - -
( 1 6 . 5 - 2 9 . 6 )
ef f luen t > 100 > 100 > 100 > 100 > 100
W W T P B co n t ro l
i n f l u e n t 4 4 . 6 1 6 . 0 3 8 . 0 < 2 5 - -
( 3 2 . 9 - 9 2 . 3 ) ( 1 2 . 0 - 2 5 . 0 ) ( 2 5 . 0 - 5 0 . 0 )
ef f luen t 52 .9 > 100 > 100 > 100 > 100
( 0 - 1 0 0 )
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Waste contribution to effluent toxicity
721
Table 4. Effect on the survival and reproduction of Ceriodaphnia
dubia and the growth of Selenastrum caprieornutum of effluents rom
WWTPs and CAS units
Ceriodaphnia Selenastrum
ECs0 ECs0
Treatment ( ) ( )
Wastewater treatment plants
WWTP A effluent 24 > 100
(16.8-36.9)
WWTP B effluent 22 13
(8.4-58.4) (9.0-17.8)
CAS u n i t s
WWTP A control 33 > 100
(25.0-50.0)
WWTP A + 4 x plant waste 46 > 100
(25.0-50.0)
WWTP A + 16 × plant waste 13 > 100
(9.6-18.7)
WWTP B control 16 72
(12.5 25 .0 ) (60.8-86.1)
WWTP B + 4 x plant waste 35 59
(27.6-45.3) (46. 74.8)
WWTP B + 16 x plant waste 28 58
(20.5-37.1) (49.4-67.0)
4 x plan t waste and 28 for the 16 x plant waste
CAS unit effluent (Table 4).
Toxicities of WWTP A and B effluents to
S e l e -
n a s t r u m c a p r i c o r n u t u m
differed (Table 4). The ECs0
concentr ations were > 100 in WW TP A effluent
and 13 in WW TP B effluent. The control CAS units
reflected this difference in effluent toxicity. Ef fluent
from the WWTP A control CAS unit were also
nontoxic to algae with 4-day ECs0 concentrat ions
exceeding 100 effluent. With WWT P B influent, the
control CAS unit effluent was less toxic to algae than
the actual WWT P effluent. The ECs0 concentrati on of
the WWTP B effluent was 13 effluent while the
control CAS unit effluent EC50 level was 72 .
In WW TP A CAS units, all algal CAS un it effluent
ECs0 concentr ations exceeded 100 effluent (Table
4). In WWTP B CAS units, algal chronic ECs0
concentr ation s were similar at 72, 59 and 58 in the
ambien t, 4 x and 16 x pla nt waste units (Table 4).
Regression of effluent toxicity to Cer ioda phnia and
Selenastrum on infiuent manufacturing plant waste
levels and effluent surfactant concen trat ions indicated
the lack of a statistically significant relationship
between toxicity and the level of plant waste com-
ponents in the influent or effluent (Table 5).
DISCUSSION
Federal and state agency regulati on of effluents has
expanded to include the moni torin g and regulation of
whole effluent toxicity (U.S. EPA, 1984, 1985). Tech-
Table 5. Regressionstatistics (r; Pearsoncorrelation
coefficients) describing the regression of toxicity
(ECs0) to Ceriodaphniaand Selenastrumon influent
manufacturingplantwaste levelsand effluentsurfac-
tant concentrations
Correlation coefficient(r)
Species lnfluent Effluent
Ceriodaphnia 0.03 0.05
Selenastrum 0.28 0.15
niques used to control whole effluent toxicity at
municipal WWTPs include utilization of alternative
treatment options to remove final effluent toxicity
and chemical identification and remediation of efflu-
ent compounds causing toxicity (U.S. EPA, 1985;
Mount and Anderson-Carnahan, 1988). These tech-
niques are useful and effective a t controlling effluent
toxicity. However, in some cases a more cost effective
and direct approach to cont roll ing effluent toxicity,
source reduction, is recommended (U.S. EPA Science
Adviso ry Board, 1988). In this approach , the waste
streams contributing to final effluent toxicity would
be identified and regulated.
Interpretation of the results of toxicity tests on
municipal WWTP influent waste streams is not
straightforward. Due to the potential chemical com-
plexity of a waste stream, the differential impact of
treatment on the components of the waste, and the
effect of the effluent matrix on the toxicity of waste
components, the waste treatment process should be
incorporated in evaluating the contribution of a
waste stream to final effluent toxicity.
Laboratory-scale, con tinuou sly fed activated
sludge treatment systems (CAS units) have been
validated as effective models of the activated sludge
process giving removals of conventio nal parameters
and consumer product chemicals similar to actual
WWTPs (King, 1980; Vashon
e t a l .
1982). In this
study, we demonstrated the utility of CAS units to
assess the contribution of a specific WWTP influent
waste stream to post-treatment toxicity by verifying
that, for Ceriodaphnia and Selenastrum, CAS units
generate effluent toxicologically similar to actual
WW TP effluents. For Ceriodaphnia, effluent toxicity
in the control CAS units and the actual WWTPs were
similar for both influent sources. For algae, although
some differences between toxicity in the WWTP s and
the control CAS unit effluents were observed, effluent
toxicities were comparable for an influent source. At
WWTP A, both control CAS unit and the actual
WWTP effluents had similar toxicity to algae with
ECs0 conce ntrat ions exceeding 100 effluent. The
WWTP B control CAS uni t effluent was less toxic to
algae tha n the actual WW TP effluent. However, given
the possible variability in effluent toxicity and in the
toxicity test, algal toxicity of the control CAS units
and the actual WWTP effluents were comparable.
Effluents of increasing manufactur ing plant waste
strength were generated by exaggerating influent
plant waste loadings to CAS units. There was no
overall effect of plant waste components on toxicity.
However, effluent from W WT P A CAS un it receiving
the 16-fold addition of plant waste and having the
highest effluent total surfactant concentrations did
have increased toxicity to Ceriodaphnia relative to
effluent from the WWTP A control CAS unit. A
4-fold addition of manufacturing plant waste to
untreated influent had no effect on the toxicity of the
WWTP A CAS unit effluent. Thus, the current level
of detergent manufacturing plant waste being re-
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722 DONALD J. VERSTEEGand DANIELM . WOLT RING
c e i v e d a t W W T P A i s n o t i m p a c t i n g e f fl u e n t t o x i c it y .
I n f a c t , a 4 - f o l d i n c r e a s e i n i n f lu e n t p l a n t w a s t e l e v e l s
w o u l d n o t b e e x p e c t e d t o i m p a c t e f f l u e n t t o x i c i t y .
I n t h e W W T P B C A S u n i t s , i n c r e a s e s i n p l a n t
w a s t e l e v e l s i n c l u d i n g t h e 1 6 - f o l d a d d i t i o n d i d n o t
a d v e r s e l y im p a c t e f f lu e n t t o x i c it y t o a l g a e o r C e r i o -
d a p h n i a . T h e r e a s o n f o r t h e 1 6 x p l a n t l e ve l c o n -
t r i b u t i n g t o e ff lu e n t t o x i c i ty i n W W T P A b u t n o t
W W T P B is n o t k n o w n b u t m a y h a v e b e e n d u e t o
i n c r e a s e d le v e ls o f m a n u f a c t u r i n g p l a n t w a s t e i n t h i s
ef f luent .
D u e t o a d d i t i o n o f p l a n t w a st e s to C A S u n i t
i n f l u e n t s , C A S u n i t e f f l u e n t s c o n t a i n e d g r e a t l y i n -
c r e a s e d c o n c e n t r a t i o n s o f t w o d e t e r g e n t a c t i v e s ,
l i n e a r a l k y l b e n z e n e s u l f o n a t e a n d d i t a l l o w d i m e t h y l
a m m o n i u m c h l o ri d e D T D M A C ) , i n c o m p a r i s o n t o
t h e a c t u a l W W T P s T a b l e 2). D e s p i t e t h e s e g r e a t l y
e l e v a t e d c o n c e n t r a t i o n s o f s u r f a c t a n t s , e f f l u e n t t o x i c -
i t y t o a l g a e a n d C e r i o d a p h n i a w a s n o t a f f e c te d e x c e p t
i n t h e C A S u n i t w i t h t h e g r e a t e s t e f f l u e n t s u r f a c t a n t
c o n c e n t r a t i o n i .e . W W T P A 1 6 × p l a n t w a s t e C A S
uni t ) .
I n a l l C A S u n i t e f f l u e n t s , l i n e a r a l k y l b e n z e n e s u l -
f o n a t e c o n c e n t r a t i o n s r e m a i n e d b e l o w l e v e ls re p o r t e d
t o b e t o x i c t o a q u a t i c o r g a n i s m s M a k i , 1 97 9; H o l -
m a n a n d M a c e k , 1 9 8 0 ; T a y l o r , 1 9 8 5 ) . H o w e v e r , C A S
u n i t e ff lu e nt co n c e n t r a t io n s o f D T D M A C e x c ee d e d
l e v e ls r e p o r t e d t o b e t o x i c . L e w i s a n d W e e 1 9 8 3 )
o b s e r v ed t h a t D T D M A C c o m p l e t e ly i n h i b it e d S e l e -
n a s t r u m c a p r i c o r n u t u m g r o w t h E C l0 0 o r a l g i s t a t i c
c o n c e n t r a t i o n ) a t c o n c e n t r a t i o n s r a n g i n g f r o m 0 .7 t o
2 . 6 m g / l i n f i l t e r e d r i v e r w a t e r . I n a c h r o n i c t o x i c i t y
t e s t c o n d u c t e d i n r i v e r w a t e r , t h e D T D M A C E C s0
c o n c e n t r a t i o n t o D a p h n i a m a g n a w a s a p p r o x .
1 .0 m g /1 . I n o u r s t u d y , D T D M A C c o n c e n t r a t i o n s u p
t o 2 0 . 3 m g / l i n a C A S u n i t e f f l u e n t h a d n o e f f e c t s o n
S e l e n a s t ru m . F o r C e r i o d a p h n i a , a c o n g e n e r i c sp e c ie s
t o D a p h n i a , t h e ef fl u en t D T D M A C c o n c e n t r a t io n a t
t h e E C s 0 l e v e l o f e ff l u e n t r e a c h e d a m a x i m u m o f
3 . 0 m g /1 . T h e s e o b s e r v a t i o n s i n d i c a t e t h a t t h e w a s t e
t r e a t m e n t p r o c e s s a n d e f f lu e n t m a t r i x m a y h a v e r e -
d u c e d t h e a p p a r e n t t o x i ci t y o f D T D M A C . T h i s ef fe ct
o n t o x i c i ty i s p r e s u m e d t o b e d u e t o a n e f f ec t o n
D T D M A C s p e c ia t i o n a n d b i o a v a i la b i l it y . S i m i l ar
r e s ul t s o n t h e a m e l i o r a t i o n o f t h e t o x i c i t y o f c a t i o n i c
c o m p o u n d s b y s u s p e nd e d s o l id s an d o r g a n i c c a rb o n
h a v e b e e n r e p o r t e d C a r y e t a l . 1987) . S ince the se
f a c t o r s a f fe c t t h e t o x i c i t y o f th e s e c o m p o u n d s i n t h e
e n v i r o n m e n t , i t i s i m p o r t a n t t o u t i l i z e t h e m o s t
e n v i r o n m e n t a l l y r e l e v a n t m e t h o d t o i n t ro d u c e t h e s e
c o m p o u n d s i n t o a q u a t i c t o x i c i t y t e s t s y s t em s . T h e s e
r e s u l t s s u g g e s t t h a t C A S u n i t s a r e a n e f f e c ti v e m e t h o d
f o r g e n e r a t i n g i n c r e a s e d c o n c e n t r a t i o n s o f t e s t m a t e -
r i a ls in a n e n v i r o n m e n t a l l y r e a li s ti c m a t r i x a n d t h a t
r e l e v a n t s a f e t y d a t a c a n b e o b t a i n e d w i t h t h e s e
m e t h o d s .
I n t h i s c a s e s t u d y , e f f l u e n t c o n c e n t r a t i o n s o f t h e
m a j o r p l a n t w a s t e c o m p o n e n t s c o u l d b e m e a s u r e d .
H o w e v e r , i f p l a n t w a s t e c o m p o n e n t s c o u l d n o t b e
m e a s u r e d d u e t o t h e n u m b e r o f c o m p o u n d s o r t h e
i n a b i l i t y to a c c u r a t e l y q u a n t i f y s p e ci fi c c o m p o n e n t s ,
t h e C A S u n i t a p p r o a c h w o u l d r e m a i n v a li d . D u e t o
t h e a b i l i t y to m a n i p u l a t e i n f lu e n t w a s t e l o a d i n g s , t h e
C A S u n i t a p p r o a c h c a n b e a p o w e r f u l t o o l t o a s s e s s
t h e c o n t r i b u t i o n o f w a s t e c o n t r i b u t o r s t o e f f lu e n t
t o x i c it y . In u t i li z i n g t h i s a p p r o a c h , c a r e s h o u l d b e
e x e r c i s e d t o a v o i d e f f e c t s o f t h e w a s t e o n t h e t r e a t -
m e n t p r o ce s s . A d d i t i o n o f w a s t e a t a b n o r m a l l y h i g h
l e v e ls c o u l d c a u s e e f f ec t s i n c l u d i n g t o x i c i t y t o a c t i -
v a t e d s l u d g e o r g a n i s m s , a l t e r n a t iv e s u b s t r a t e u t i l iz a -
t i o n o r d i l u t i o n o f i n fl u e n t a n d m i x e d l i q u o r s t re n g t h .
T h e s e , a n d o t h e r p o t e n t i a l e f f ec ts , c o u l d a m e l i o r a t e o r
p o t e n t i a t e t h e o b s e r v e d t o x i c i t y o f t h e w a s t e . T h e
i n c i d e n c e o f t h e s e e f f e c t s c a n b e r e d u c e d b y p r o p e r
s e l e ct i o n o f i n f lu e n t w a s t e l e v el s a n d m o n i t o r i n g o f
a c t i v a t e d s l u d g e p r o c e s s e s .
CONCLUSIONS
U s e o f l a b o r a t o r y - s c a l e , c o n t i n u o u s a c t i v a t e d
s l u d g e u n i t s c o u p l e d w i t h e f f l u e n t t o x i c i t y te s t p r o c e -
d u r e s w e r e e ff e c ti v e m e t h o d s t o a s s e s s t h e c o n t r i b u -
t i o n o f a n i n f lu e n t s o u r c e t o f in a l W W T P e f fl u en t
t o x i c it y . C A S u n i t s p r o v i d e d t r e a t m e n t o f i n fl u e n t
w a s t e s t r e a m s a n d g e n e r a t e d t o x i c o l o g i c a l l y r e l e v a n t
e f fl u en t s f o r C e r i o d a p h n i a a n d S e l e n a s tr u m . A m a j o r
c o m p o n e n t o f th e d e t e r g e n t m a n u f a c tu r i n g p l a n t
w a s te , D T D M A C , w a s l es s t o x ic as a c o m p o n e n t o f
a C A S u n i t e f f l u e n t t h a n h a s b e e n r e p o r t e d i n t h e
l i t e r a t u r e i n c o n v e n t i o n a l l a b o r a t o r y t o x i c i t y t e s t s
s u g g e s ti n g t h a t c o m p o n e n t s o f W W T P e f fl u e nt s a m e -
l i o r a t e t h e t o x i c i t y o f t h i s s u r f a c t a n t . I n t h i s c a s e
s t u d y , t h e d e t e r g e n t m a n u f a c t u r i n g p l a n t w a s t e w a s
n o t a s i g n i fi c a n t c o n t r i b u t o r t o W W T P e f fl u e nt to x i -
c i ty a t c u r r e n t r a t es o f m a n u f a c t u r i n g p l a n t w a s t e
i n p u t t o t h e W W T P .
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