BOD
5
and COD removal and sludge production
in SBR working with or without anoxic phase
Dorota Kulikowska
a,*
, Ewa Klimiuk
a
, A. Drzewicki
b
a
Department of Environmental Biotechnology, University of Warmia and Mazury in Olsztyn, Sloneczna St. 45G, 10-709 Olsztyn, Poland
b
Department of Applied Ecology, University of Warmia and Mazury in Olsztyn, Oczapowskiego St. 5, 10-957 Olsztyn, Poland
Received 27 May 2004; received in revised form 2 April 2006; accepted 12 May 2006
Available online 5 July 2006
Abstract
The aim of this study was to estimate the BOD
5
and COD removal efficiency and biomass yield coefficient in sequencing batch reac-
tors (SBR) treating landfill leachate.
Experiments were carried out in four SBRs at HRT of 12, 6, 3 and 2 d. Two series were performed. In series 1, the reactors were
operated in a 24 h cycle mode (anoxic 3 h, aeration 18 h, settling 2.75 h, and discharge 0.25 h). In series 2, however, the anoxic phase
was eliminated.
In both series the BOD
5
removal efficiency was almost identical – over 98%. On shortening HRT from 12 to 2 d, COD removal effi-
ciency decreased from 83.1% to 76.7% (series 1). In series 2, efficiency ranged from 79.6% to 75.7%. In the reactors working with the
anoxic phase the observed biomass yield coefficient (Y
obs
) was nearly constant (0.55–0.6 mg VSS/mg COD). Upon elimination of the
anoxic phase, the Y
obs
was observed to decrease from 0.32 mg VSS/mg COD (HRT 2 d) to 0.04 mg VSS/mg COD (HRT 12 d).
2006 Elsevier Ltd. All rights reserved.
Keywords: Landfill leachate; Sequencing batch reactor (SBR); BOD
5
and COD removal; Observed yield coefficient; Biomass decay rate
1. Introduction
A major problem usually associated with the disposal of
waste by sanitary landfill is the pollution of groundwater
and surface waters if leachate is discharged into these water
bodies. Many cases of leachate impact on surface water
and groundwater quality may be linked to improper or
insufficient landfill technology. Careful site management
can reduce the amount and strength of the leachate produc-
tion but cannot eliminate it. Some form of treatment is,
therefore, necessary if the receiving waters are to be pro-
tected. Currently, leachates are treated by biological and
physico-chemical methods. Among the most commonly
used are activated sludge (
) or a combination of different technologies such as
biological treatment, electron-beam radiation and chemical
oxidation (
Bae et al., 1999; Kennedy and Lentz, 2000; Lin
In multi-stage systems, pollutant elimination by biolog-
ical oxidation is a predominant process in wastewater treat-
ment technology. In this process new cells (sludge) are the
one of the final products. Landfill leachate contains xeno-
biotic organic compounds and heavy metals (
2004; Jensen and Christensen, 1999; Paxe´us, 2000
). Many
such pollutants are hydrophobic and the principal removal
mechanism for these compounds is sorption to sludge par-
ticles and transfer to the sludge processing system. It can
negatively influence the quality of sludge composition
and impose restrictions in relation to disposal of the excess
sludge and further waste management.
On the other hand, with rising costs of sludge disposal,
the minimization of sludge production has become
of increasing importance. The expense of excess sludge
0960-8524/$ - see front matter
2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.biortech.2006.05.021
*
Corresponding author. Tel.: +48 89 5234145.
E-mail address:
(D. Kulikowska).
Bioresource Technology 98 (2007) 1426–1432
treatment has been estimated to be 50–60% of the total cost
of municipal wastewater treatment (
).
Therefore, modification of the aerobic treatment process
in order to reduce biosolids production seems to be highly
interesting.
The important strategies for minimization of excess
sludge production are lysis-cryptic growth, uncoupling
metabolism and maintenance metabolism and predation
of bacteria (
). It is commonly known that
increase of sludge age is associated with decreased sludge
production (
). In addition,
showed that reduction of excess sludge
production can be achieved by raising the concentration of
dissolved oxygen in the mixed liquor. In a reactor with a
sludge loading of 1.7 mg BOD/mg MLSS Æ d, an increase
in the dissolved oxygen concentration from 2 to 6 mg/l
caused a reduction in the amount of solids in the reactor
by about 25%.
In activated sludge models yield and decay coefficients
must be determined empirically. Until now, investigations
concerned municipal wastewater. However, literature data
show a lack of investigation of the yield of activated sludge
in landfill leachate treatment. Toxicity of the landfill leach-
ate has been extensively studied and well documented (
nard et al., 1996; Isidori et al., 2003; Marttinen et al., 2002;
Silva et al., 2004
). It can influence the growth and decay of
microorganisms.
The aim of this study was to investigate the BOD
5
and
COD removal efficiency and biomass yield coefficient in
sequencing batch reactors (SBRs) treating landfill leachate.
In the experiment, anaerobic–aerobic (with anoxic and aer-
ation phases in the cycle) and aerobic systems (without
anoxic phase) were tested. Unlike conventional systems,
SBRs offer various advantages, including minimal space
requirements and ease of management (
). Their additional benefit is the possibility of techno-
logical modifications during the process, since very signifi-
cant changes in the chemical composition of leachate may
occur throughout landfill exploitation.
The removal efficiency for BOD
5
and COD, depending
on reactor cycle working with or without the anoxic phase,
was estimated at different hydraulic retention times (HRT)
in the SBRs. The observed biomass yield coefficients (Y
obs
),
the values of biomass yield coefficients Y and biomass
decay rates k
d
were determined.
2. Methods
2.1. Leachate feed
Leachate used in this study was collected from a muni-
cipal landfill located in Wysieka near Bartoszyce in the
Warmia and Mazury Province, Poland. The landfill had
been operated since January 1996.
Throughout the experimental period, COD and BOD
5
were 1380 mg COD/l (S.D. 80.4) and 539 mg BOD
5
/l
(S.D. 37.3), respectively, in series 1, and 1188 mg COD/l
(S.D. 38.97) and 451 mg BOD
5
/l (S.D. 34.04), respectively,
in series 2. The BOD
5
/COD ratios in leachate were 0.39
(S.D. 0.01) (series 1) and 0.38 (S.D. 0.03) (series 2). Bio-
chemical oxygen demand rate constants (k) were deter-
mined from the first-order kinetics equation and reached
0.44 d
1
(series 1) and 0.41 d
1
(series 2) (
). The rate
constant k is a parameter determining the course of BOD
and thus also the BOD
5
value. In the literature, it is usually
stated that the value of k depends primarily on the rate at
which the organic substances can be oxidized biologically.
Thus, for instance, in the raw municipal wastewater, values
of k are much higher (0.3–0.5 d
1
) than in the same waste-
water after biological treatment (0.2 d
1
). In some indus-
trial wastewater containing primarily slowly degradable
compounds, k values can be lower than 0.2 d
1
2.2. Process configuration and system design
The investigations were carried out at bench scale in
four SBRs operated in parallel (SBR 1–SBR 4). The reac-
tors, with a working volume of 6 l each, were made of
plexiglass and were equipped with a stirrer at regulated
rotation speed (36 rpm). Dissolved oxygen was supplied
using porous diffusers, placed at the bottom of the reactors.
The leachate was supplied to the reactors by means of a
peristaltic pump (ZALIMP type pp 1–05) for 4 h of the
cycle at 0.125 l/h (SBR 1), 0.25 l/h (SBR 2), 0.5 l/h (SBR
3) and 0.75 l/h (SBR 4). The amount of the leachate sup-
0
100
200
300
400
500
600
700
800
0
2
4
6
8
10
12
14
16
18
20
time [d]
time [d]
BOD [mgO
2
/ l]
first-order kinetic
experimental data
k = 0.44 d
-1
-1
0
100
200
300
400
500
600
700
800
0
2
4
6
8
10
12
14
16
18
20
BOD [mgO
2
/ l]
first-order kinetic
experimental data
k = 0.41 d
(a)
(b)
Fig. 1. Experimental data, biochemical oxygen demand curves and
constant k determined from first-order kinetics (a. series 1, b. series 2).
D. Kulikowska et al. / Bioresource Technology 98 (2007) 1426–1432
1427
plied within 24 h to the reactors varied from 0.5 l (SBR 1)
to 3 l (SBR 4). Hydraulic retention time of the leachate ran-
ged from 12 d (SBR 1) to 2 d (SBR 4) (
Two series were performed. In series 1, the reactors were
operated in a 24 h cycle mode, at 3; 18; 2.75 and 0.25 h for
the anoxic, aeration, settling and discharge, respectively. In
series 2, the anoxic phase was omitted and the time of the
operating phases of the cycle was as follows: 21 h for aera-
tion, 2.75 h for settling and 0.25 h for discharge. In the aer-
ation phase, the amount of oxygen supplied to the reactor
was regulated in order to maintain the oxygen concentra-
tion at the end of the phase at 2.5–4.0 mg O
2
/l. The system
was operated at room temperature (20–22
C) for two
months.
2.3. Analytical methods
2.3.1. Chemical analysis
Daily measurements of effluent from the SBR included:
• chemical oxygen demand (COD) (according to
),
• biochemical oxygen demand BOD
5
(according to DIN
EN 1899-1/EN 1899-2 official EPA method using Oxi-
Top
made by WTW company (WTW Wissenschaft-
lich–Technische
Werkstra¨tten
Gmbh,
D-82326
Weilheim, Germany)),
• volatile suspended solids (VSS) and total suspended sol-
ids (TSS) in the settled effluent (according to
).
The mixed reactor content was analysed for:
• volatile suspended solids (MLVSS) and total suspended
solids (MLSS) (according to
• oxygen concentration (using an oxygen controller HI
9142 made by Hanna Instruments (Hanna Instruments
S.p.A, 35030 Sarmeola di Rubano, Padova, Italy)).
2.3.2. Biological analysis
The research on activated sludge biocenosis encom-
passed a microscopic analysis of quantitative composition
of rhizopods, ciliates and metazoans. Microfauna composi-
tion was determined ‘in vivo’. Number of organisms was
calculated from microscope slides, containing 0.05 ml of a
well-mixed sample at microscope magnifications ranging
from
·100 to ·400, depending on organism size.
The numbers of rhizopods, ciliates and metazoans were
estimated as arithmetic averages obtained from analysis of
four subsamples with volume of 0.05 ml mixed liquor. The
number of colonial species (Opercularia sp., Epistylis sp.,
Carchesium sp.) was calculated as the sum of all individuals
in a colony. Finally, total number of organisms was recal-
culated per l (ind./l) and mg of VSS (ind./mg VSS).
3. Results and discussion
3.1. BOD
5
and COD removal
In this study, leachate originated from a municipal land-
fill operated for five years. It is known that the leachate
from young landfills (up to five years) contains biodegrad-
able organic substances at very high concentration, even
over 10,000 mg COD/l (
). In the
present investigation, the content of organic compounds
was up to 1400 mg COD/l, but BOD
5
and COD removal
efficiency was relatively high.
Under anaerobic–aerobic conditions (series 1), the effi-
ciency of BOD
5
removal ranged from 99.2% (at the reten-
tion time of 12 d – SBR 1) to 97.6% (at the retention time
of 2 d – SBR 4) (
). The COD removal efficiency
decreased from 83.1% (SBR 1) to 76.7% (SBR 4) (
).
Under aerobic conditions (aeration phase only) (series 2),
the BOD
5
removal efficiency was almost identical to that
in series 1 (
). However, a slight decrease in the effi-
ciency of COD removal was observed in all SBRs (
).
The results of
on municipal
wastewater treatment in SBR indicate that an increase in
duration of the aeration phase of the cycle from 61% to
67% caused a 5% increase in COD removal efficiency. In
the present experiment, a higher efficiency was obtained
under anaerobic–aerobic conditions. The highest differ-
ences in the efficiency of COD removal between series 1
and 2 were obtained at HRT of 12 d (SBR 1) (
). In
all SBRs sludge age was over 2-fold longer in series 2 than
in series 1.
In wastewater effluents, the non-biodegradable fraction
is constituted of compounds present in the raw wastewater
plus those non-biodegradable substances produced by the
microorganisms. These soluble microbial products (inter-
mediates or final products of substrate degradation and cell
Table 1
Technological parameters in series 1 and 2
Parameters
Units
Series 1
Series 2
SBR 1
SBR 2
SBR 3
SBR 4
SBR 1
SBR 2
SBR 3
SBR 4
Volume of leachate influent in SBR operating cycle
l
0.5
1.0
2.0
3.0
0.5
1.0
2.0
3.0
Hydraulic retention time (HRT)
d
12
6
3
2
12
6
3
2
Volatile suspended solids
g MLVSS/l
1.99
2.61
3.45
3.90
1.65
2.12
3.57
3.84
Solid retention time (SRT)
d
33
22
15
11
80
56
38
30
1428
D. Kulikowska et al. / Bioresource Technology 98 (2007) 1426–1432
decomposition) are very important owing to their influence
on the quality of effluent from biological treatment
processes.
showed that the amount of soluble
microbial products (SMP) in the effluent from a SBR
depends on the sludge age. The minimum SMP concentra-
tions could be achieved at sludge ages ranging between 5 d
and 15 d. At sludge ages below 5 d and above 15 d SMP
concentration increased.
3.2. Biomass yield coefficient
The observed biomass yield coefficient Y
obs
is the mass
of bacteria formed per mass of COD removed and it
involves the energy requirements. The value of the
observed biomass yield coefficient Y
obs
corresponds to net
biomass yield coefficient and can be calculated from the
following equation:
Y
obs
¼
X
org
ðV
w
=t
c
Þ þ X
e
ðV
eff
=t
c
Þ
ðC
s
C
e
Þ ðV
in
=t
c
Þ
;
ð1Þ
where
Y
obs
observed
biomass
yield
coefficient
(mg VSS/
mg COD),
X
org
volatile suspended solids in SBR (mg VSS/l),
V
w
volume of suspended solids disposed in SBR oper-
ating cycle (l),
t
c
time of SBR operating cycle (d),
X
e
effluent volatile suspended solids concentration
(mg VSS/l),
V
eff
volume of leachate effluent in SBR operating cycle
(l),
V
in
volume of leachate influent in SBR operating cycle
(l), (V
in
= V
eff
+ V
w
),
C
s
concentration of COD in raw leachate (mg COD/
l),
C
e
concentration of COD in the effluent (mg COD/l).
In series 1, the observed biomass yield coefficient Y
obs
was almost stable (0.55–0.6 mg VSS/mg COD) (
irrespective of the leachate retention time (changing from
12 d to 2 d) and the sludge age ranging from 33 d to
11 d, respectively. It means that in this series 55–60% of
COD was converted to biomass during the leachate treat-
ment process.
Under aerobic conditions (series 2), a significant
decrease was observed in the value of Y
obs
, which corre-
sponded with the increase in the hydraulic retention time
in the reactors. The Y
obs
values reached 0.32 mg VSS/
mg COD and 0.04 mg VSS/mg COD at the leachate
hydraulic retention times of 2 d and 12 d, respectively
(
). Thus, in order to maintain the concentration of
volatile suspended solids in the SBR at a level comparable
with that in series 1, it was necessary to increase the sludge
age (
The results of a study by
, including
both protein solution and raw sewage as substrates, indi-
cated that the observed yield coefficients were 35–52%
higher for anoxic reactors than for aerobic reactors.
Anoxic conditions or anoxic zones are widely applied in
activated sludge systems with denitrification and phospho-
rus removal.
indicated the possibility of
minimizing the sludge production in aerobic wastewater
treatment through manipulation of the ecosystem, so that
most of the bacterial biomass produced is consumed by
predating protozoa and metazoa. In this way, the biomass
90
92
94
96
98
100
SBR 1
SBR 2
SBR 3
SBR 4
BOD
5
removal efficiency [%]
series 1
series 2
Fig. 2. BOD
5
removal efficiency in series 1 and 2.
60
65
70
75
80
85
90
SBR 1
SBR 2
SBR 3
SBR 4
C
O
D
r
em
oval
e
ff
iciency [
%
]
series 1
series 2
Fig. 3. COD removal efficiency in series 1 and 2.
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
Y
obs
[mgV
SS/m
g
C
OD]
SBR 1
SBR 2
SBR 3
SBR 4
series 1
series 2
Fig. 4. Observed biomass yield coefficient Y
obs
in series 1 and 2.
D. Kulikowska et al. / Bioresource Technology 98 (2007) 1426–1432
1429
yield coefficients obtained were 30–50% lower than those of
conventional systems.
In the present study, elimination of the anoxic phase
during the cycle period had a favourable effect on micro-
fauna (
). In activated sludge in series 1 (SBR 1), the
highest abundance of microfauna (800 ind./mg VSS) was
found at 12 d HRT and at 33 d sludge age. On the other
hand, in SBR 3 and 4 at HRT of 3 and 2 d and sludge
age of 15 and 11 d there was noticed 8-fold and 10-fold
smaller microfauna abundance in comparison with SBR
1. However, in series 2 the abundance increased slightly
from 878 to 986 ind./mg VSS with HRT shortened from
12 to 2 d. Comparing the total abundance in both series
it can be stated that the abundance did not decrease below
800 ind./mg VSS at sludge age not shorter than 30 d.
, on the basis on his own and others’
research, concluded that abundance of ciliates in properly
functioning activated sludge plants treating municipal
wastewater should be 10
6
ind./l. In the present work the
abundance of protozoan communities in series 1 ranged
from 3.24
· 10
5
to 1.59
· 10
6
ind./l (from 83 to 800 ind./
mg VSS) and in series 2 from 1.45
· 10
6
to 4.77
· 10
6
ind/
l (from 878 to 986 ind./mg VSS).
In the present study, the highest differences in Y
obs
were
seen in SBR 1 in series 1 and 2, with comparable abun-
dance of microfauna. It means that in such conditions
sludge
production
depends
on
factors
other
than
predation.
For a steady state system, the observed yield coefficient
in activated sludge is primarily determined by the sludge
age. Longer sludge ages result in decrease of the sludge
mass by endogenous metabolism. Losses of biomass by
endogenous metabolism can be expressed by means of spe-
cific decay rate k
d
. There is a correlation between sludge
age, biomass yield coefficient (Y) and loss of biomass
expressed by means of biomass decay rate k
d
. The values
of both parameters (Y and k
d
) can be calculated from the
following equation:
1
H
¼ Y
ðC
s
C
e
Þ ðV
d
=t
c
Þ
V
X
org
k
d
;
ð2Þ
where
H
solids retention time (SRT) (d),
Y
biomass yield coefficient (mg VSS/mg COD),
C
s
concentration of COD in raw leachate (mg COD/
l),
C
e
concentration of COD in the effluent (mg COD/l),
V
d
volume of leachate influent in SBR operating cycle
(l),
t
c
time of SBR operating cycle (d),
V
working volume of SBR (l),
X
org
volatile suspended solids in SBR (mg VSS/l),
k
d
biomass decay rate (d
1
).
The results indicate that in both series the values of Y
were almost the same. The biomass yield coefficient was
0.628 mg VSS/mg COD in series 1 and 0.616 mg VSS/mg
COD in series 2 (
).
The elimination of the mixed phase (series 2) was
observed to affect the value of the biomass decay rate k
d
.
0
200
400
600
800
1000
1200
1
2
3
4
1
2
3
SBR No.
total n
u
mbet o
f
micro
faun
a
[i
nd./m
g
VSS]
se
ries 2
series 1
4
Series 1
Series 2
Taxons Unit
SBR 1
SBR 2
SBR 3
SBR 4
SBR 1
SBR 2
SBR 3
SBR 4
Rhizopoda
ind./mg
VSS
27 28 - - 32 18 23 3
Ciliata
ind./mg
VSS 762 524 100 83 769 848 927 970
Metazoa
ind./mg
VSS
11 2 - - 77 36 18 13
Fig. 5. Total number of microfauna in activated sludge in series 1 and 2 (The table includes composition of Protozoa and Metazoa in activated sludge.)
Table 2
Values of biomass yield coefficient Y, biomass decay rate k
d
and specific
maintenance coefficient m in series 1 and 2
Series no.
Y
(mg VSS/mg COD)
k
d
(d
1
)
m
(mg COD/mg VSS Æ d)
Series 1
0.628
0.006
0.01
Series 2
0.616
0.032
0.052
1430
D. Kulikowska et al. / Bioresource Technology 98 (2007) 1426–1432
In SBR working under anaerobic–aerobic conditions (series
1) the value of k
d
reached 0.006 d
1
. Under aerobic condi-
tions (aeration phase only), an over 5-fold increase in the
k
d
value (up to 0.032 d
1
) was observed (
).
For heterotrophic bacteria, the decay rate is in the range
of 0.3–0.7 d
1
, whereas for nitrifying bacteria and polyphos-
phate accumulating organisms – 0.15–0.2 d
1
, according to
(after
).
showed experimentally that
the average autotrophic decay rates in aerobic, anoxic and
anoxic/aerobic reactors were 0.153, 0.097, and 0.058 d
1
,
respectively.
pointed out that at 20
C
the decay rate of nitrification activity reduces from about
0.2 to 0.03 d
1
from aerobic to anaerobic conditions,
respectively.
On the basis of Y and k
d
specific maintenance coefficient
m was calculated (
). The maintenance coefficient
reflects a recently introduced concept called maintenance
energy. Maintenance energy can be defined as the mini-
mum input of energy into the culture that is necessary for
the basic biochemical processes to continue in cells. In
the activated sludge process, the specific maintenance
coefficient of the entire mixed culture of activated sludge
represents a minimum sludge loading, i.e., a minimum
mass of substrate applied to mass unit of biomass per unit
of time (
). As yield coefficient Y is rather con-
stant, the microorganisms with the higher decay rate k
d
require higher maintenance energy. In series 1 m was
0.01 mg COD/mg VSS Æ d. After changing conditions to
aerobic (series 2), over a 5-fold increase of specific mainte-
nance coefficient m was noticed.
4. Conclusions
The results of the study can be summarised as follows:
1. Operational conditions had nearly no effect on the
BOD
5
removal efficiency, but affected the COD removal
efficiency. The results revealed that lower COD removal
efficiency was achieved in the SBRs working without the
anoxic phases (aerobic conditions), in which at given
HRT sludge age was over 2-fold higher.
2. The application of the anoxic phase in the work cycle of
the SBR caused the observed yield Y
obs
to change
slightly from 0.55 mg VSS/mg COD to 0.6 mg VSS/
mg COD with decreasing HRT. After anoxic phase
elimination, the observed yield increased with shorten-
ing HRT (from 0.04 mg VSS/mg COD to 0.32 mg
VSS/mg COD). The highest differences as a result of
changing operational conditions were obtained at 12 d
HRT, when microfauna abundance in both SBRs was
comparable. It indicates that the predation of bacteria
in activated sludge is not the most important factor
determining sludge production.
3. The sludge yield Y obtained in the SBR working with
the anoxic and aeration phases equalled 0.628 mg VSS/
mg COD, whereas it was 0.616 mg VSS/mg COD in
the SBR working without the anoxic phase. The change
of anoxic conditions for aerobic resulted in an increase
in substrate utilization for biomass production. It
caused a significant increase in the biomass decay rate
k
d
from 0.006 d
1
(series 1) to 0.032 d
1
(series 2), after
the elimination of the anoxic phase in the work cycle of
the SBRs.
4. During municipal leachate treatment aerobic conditions
in SBRs should be considered as optimal owing to
clearly lower biomass production with comparable effec-
tiveness of BOD
5
and COD removal.
References
Abbassi, B., Dullstein, S., Ra¨biger, N., 1999. Minimization of excess
sludge production by increase of oxygen concentration in activated
sludge flocs; experimental and theoretical approach. Wat. Res. 34 (1),
139–146.
Amokrane, A., Comel, C., Veron, J., 1997. Landfill leachates pretreatment
by coagulation – flocculation. Wat. Res. 31 (11), 2775–2782.
Bae, B-U., Jung, E-S., Kim, Y-R., Shin, H-S., 1999. Treatment of landfill
leachate using activated sludge process and electron-beam radiation.
Wat. Res. 33 (11), 2669–2673.
Baun, A., Ledin, L.A., Bjerg, P.L., Christensen, T.H., 2004. Xenobiotic
organic compounds in leachates from ten Danish MSW landfills –
chemical analysis and toxicity tests. Wat. Res. 38, 3845–3858.
Bernard, C., Guido, P., Colin, J., Le Duˆ-Delepierre, A., 1996. Estimation
of the hazard of landfills throughout toxicity testing of leachates. I
Determination of leachate toxicity with a battery of acute tests.
Chemosphere 33, 2303–2320.
Doyle, J., Watts, S., Solley, D., Keller, J., 2001. Exceptionally high-rate
nitrification in sequencing batch reactors treating high ammonia
landfill leachate. Wat. Sci. Technol. 43 (3), 315–322.
Egemen, E., Corpening, J., Nirmalakhanden, N., 2001. Evaluation of an
ozonation system for reduced waste sludge generation. Wat. Sci.
Technol. 44 (2–3), 445–452.
Henze, M., Gujer, W., Mino, T., Matsuo, T., Wentzel, M.C., Marais, G.,
1995. Activated sludge model No. 2. Scientific and Technical Report,
No 3. IAWQ, London, England, UK.
Hermanowicz, W., Do_zn´ska, W., Dojlido, J., Koziorowski, B., 1999.
Fizyczno – chemiczne badanie wody i s´cieko´w. Arkady. Warszawa,
Poland.
Hosomi, M., Matsusige, K., Inamori, Y., Sudo, R., Yamada, K., Yoshino,
Z., 1989. Sequencing batch reactor activated sludge processes for the
treatment of municipal landfill leachate: removal of nitrogen and
refractory organic compounds. Wat. Sci. Technol. 21, 1651–1654.
Imai, A., Iwami, N., Matsushige, K., Inamori, Y., Sudo, R., 1993.
Removal of refractory organic and nitrogen from landfill leachate by
the microorganism-attached activated carbon fluidized bed process.
Wat. Res. 27 (1), 143–145.
Im, J.-H., Woo, H.-J., Choi, M.-W., Han, K.-B., Kim, Ch.-W., 2001.
Simultaneous organic and nitrogen removal from municipal landfill
leachate using an anaerobic–aerobic system. Wat. Res. 35 (10), 2403–
2410.
Irvine, R.L., Wilderer, P.A., Fleming, H-C., 1997. Controlled unsteady
state processes and technologies – an overview. Wat. Sci. Technol. 35
(1), 1–10.
Isidori, M., Lavorgna, M., Nardelli, A., Parrella, A., 2003. Toxicity
identification evaluation of leachates from municipal solid waste
landfills: a multispecies approach. Chemosphere 52 (1), 85–94.
Jensen, D.L., Christensen, T.H., 1999. Colloidal and dissolved metals in
leachates from four Danish landfills. Wat. Res. 33 (9), 2139–2147.
Kennedy, K.J., Lentz, E.M., 2000. Treatment of landfill leachate using
sequencing batch and continuous flow upflow anaerobic sludge
blanket (UASB) reactors. Wat. Res. 34 (14), 3640–3656.
D. Kulikowska et al. / Bioresource Technology 98 (2007) 1426–1432
1431
Lee, Y., Oleszkiewicz, J.A., 2003. Effects of predation and ORP conditions
on the performance of nitrifiers in activated sludge systems. Wat. Res.
37, 4202–4210.
Lee, N.M., Welander, T., 1996. Reducing sludge production in aerobic
wastewater treatment through manipulation of the ecosystem. Wat.
Res. 34 (8), 1781–1790.
Lin, S.H., Chang, Ch.C., 2000. Treatment of landfill leachate by combined
electro-Fenton oxidation and sequencing batch reactor method. Wat.
Res. 34 (17), 4243–4249.
Lishman, L.A., Legge, R.L., Farquhar, G.J., 2000. Temperature effects on
wastewater treatment under aerobic and anoxic conditions. Wat. Res.
34 (8), 2263–2276.
Loosdrecht, M.C.M., Henze, M., 1999. Maintenance, endogenous respi-
ration, lysis, decay and predation. Wat. Sci. Technol. 39 (1), 107–117.
Madoni, P., 1991. Role of protozoans and their indicator value in the
activated sludge process. In: Madoni, P. (Ed.), Biological Approach to
Sewage Treatment Process: Current Status and Perspectives. Centro
Bazzucchi, Perugia, Italy, pp. 21–27.
Marttinen, S.K., Kettunen, R.H., Sormunen, K.M., Soimasou, R.M.,
Rintala, J.A., 2002. Screening of physical–chemical methods for
removal of organic material, nitrogen and toxicity from low strength
landfill leachates. Chemosphere 46 (6), 851–858.
Paxe´us, N., 2000. Organic compounds in municipal landfill leachates.
Wat. Sci. Tech. 42 (7–8), 323–333.
Pitter, P., Chudoba, J., 1990. Biodegradability of organic substances in the
aquatic environment. CRC Press, Boca Raton, Boston, USA.
Pribyl, M., Tucek, F., Wilderer, P.A., Wanner, J., 1997. Amount and
nature of soluble refractory organics produced by activated sludge
microorganisms in sequencing batch and continuous flow reactors.
Wat. Sci. Tech. 35 (1), 27–34.
Rusten, B., Eliassen, H., 1993. Sequencing batch reactors for nutrient
removal at small wastewater treatment plants. Wat. Sci. Technol. 28,
233–242.
Siegrist, H., Brunner, I., Koch, G., Linh Con Phan, Van Chieu Le, 1999.
Reduction of biomass decay rate under anoxic and anaerobic
conditions. Wat. Sci. Tech. 39 (1), 129–137.
Silva, A.C., Dezotti, M., Sant’Anna Jr., G.L., 2004. Treatment and
detoxification of a sanitary landfill leachate. Chemosphere 55 (11),
207–214.
Wanner, J., 1994. Activated sludge bulking and foaming control.
Technomic Publishing Company Inc., Lancaster, Pennsylvania, USA.
Wei, Y., van Houten, R.T., Borger, A.R., Eikelboom, D.H., Fan, Y.,
2003. Minimization of excess sludge production for biological waste-
water treatment. Wat. Res. 37, 4453–4467.
1432
D. Kulikowska et al. / Bioresource Technology 98 (2007) 1426–1432
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