DSpace at VNU: Application of a partial nitritation and anammox system for the old landfill leachate treatment

International Biodeterioration & Biodegradation xxx (2014) 1e7

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Application of a partial nitritation and anammox system for the old
landfill leachate treatment
Phan The Nhat a, Ha Nhu Biec a, Nguyen Thi Tuyet Mai a, Bui Xuan Thanh b, *,
Nguyen Phuoc Dan a
a

Faculty of Environment and Natural Resources, Ho Chi Minh City University of Technology, Building B9, 268 Ly Thuong Kiet Street, District 10,
Ho Chi Minh City, Viet Nam
Division of Environmental Engineering and Management, Ton Duc Thang University, No. 19 Nguyen Huu Tho Street, Tan Phong Ward, District 7,
Ho Chi Minh City, Viet Nam

b

a r t i c l e i n f o

a b s t r a c t

Article history:
Received 15 January 2014
Received in revised form
29 May 2014
Accepted 30 May 2014
Available online xxx

This study shows high nitrogen removal efficiency of a combination of partial nitritation and Anaerobic
Ammonium Oxidation (anammox) process for old landfill leachate treatment. A lab-scale experiment
including partial nitritation using a sequencing batch reactor (PN-SBR) followed by a anammox hybrid
reactor (HAR), which consists of suspended biomass layer in the bottom part and bio-carrier bed in the
upper part run at the influent total ammonia concentrations (TAN) of 500 mg N/L and 1000 mg N/L. The
result of PN-SBR experiment showed that the NO2eN:NH4eN ratio achieved about 1.22 and 1.02 at HRT
of 12 h (influent TAN of 500 mg N/L) and HRT of 19 h (influent TAN of 1000 mg N/L), respectively.
Simultaneously, the HAR was operated at the nitrogen loading rate (NLR) of 4.2 and 8.3 kg N/m3.d,
corresponding to influent TAN of 500 mg N/L and 1000 mg N/L, respectively. The effluent of the system
containing 9.7 ± 3.5 mg NH4eN/L, 1.7 ± 0.4 mg NO2eN/L and 23 ± 4 mg NO3eN/L (equivalent to
35 ± 4 mg TN/L) at NLR of 1.02 for PN-SBR and NLR of 4.2 kg N/m3.d for HAR. This effluent quality was
good enough to meet Vietnamese treated landfill leachate quality. The system obtained TN removals of
93 ± 1% and 81 ± 1.2% at NLRs of 4.2 kg TN/m3.d (phase I) and 8.3 kg TN/m3.d (phase II), respectively. The
total biomass of HAR including attached biomass and suspended one was maintained up to
20,400 mgVSS/L at the end of the experiment when the removal rate of anamnox biomass obtained
0.4 kg TN/kgVSS.d. While, PN-SBR was kept at 2300 mg MLVSS/L and SRT of 10e12 days at NLR of
4.2 kg TN/m3.d, which the nitrogen conversion rate of AOB was 0.53 kg TAN/kgVSS.d. In terms of COD
removal, it is found that PN-SBR removed only 14% of influent COD, whereas HAR removed 30% of COD.
© 2014 Published by Elsevier Ltd.

Keywords:
Partial nitritation
Old landfill leachate
SBR and hybrid anammox reactor

1. Introduction
Sanitary landfill is the most common municipal solid waste
disposal in Vietnam. Leachate generated from the landfills has
caused serious water pollution due to high concentrations of
ammonia and slowly or non-biodegradable organic matter. High

total ammonia concentration (TAN) results in high toxicity by free
ammonia which inhibits anaerobic degradation of solid wastes and
increases dissolved oxygen depletion in the receiving water. The
ammonia concentration in the leachate varies with the age of the
landfill and it is in the range of 100e5500 mg N/L (Sri Shalini and
Joseph, 2012). In Vietnam, all leachate treatment plants have not
met the leachate quality standards (QCVN 25:2009/BTNMT) in
* Corresponding author.
E-mail addresses: (P.T. Nhat), ,
(B.X. Thanh), (N.P. Dan).

terms of the allowable ammonia (25 mgN/L) and total nitrogen
concentrations (60 mg N/L) (Monre, 2009). In Vietnam, the current
leachate treatment plants use mainly the conventional
nitrification-denitrification process, which is costly due to large
oxygen supply demand for nitrification and carbon source
requirement for denitrification. In recent years, a partial nitritation
coupled with anammox process have proven as a feasible technology for nitrogen removal in comparison to the conventional
nitrificationedenitrification process (Van Dongen, 2001; Fux et al.,
2002; Schmidt et al., 2003). This process consumed less 50% of
oxygen demand, did not use organic carbon sources, produced less
sludge amount and less CO2 emission (Reginatto et al., 2005). The
arrangement of partial nitritation and anammox processes was
done in single reactors or in two separate reactors in series. The
two-step process is recommended to avoid heterotrophic growth in
the anammox reactor as well as to enhance the NH4eN removal in
the case of high influent TKN concentration (Van Hulle et al., 2007).

/>0964-8305/© 2014 Published by Elsevier Ltd.

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Table 1
Characteristics of old landfill leachate in the study.
Parameter

Unit

Mean value ± std (n ¼ 8)

pH
Alkalinity
TKN
NH4eN (TAN)
NO2eN
NO3eN
COD
BOD5
SS

mg CaCO3/L
mg N/L
mg N/L
mg N/L
mg N/L

mg/L
mg/L
mg/L

8.4
15133
3868
3449
0.21
2.23
3621
425
59

±
±
±
±
±
±
±
±
±

0.30
58
26
233
0.01
0.18

440
72
16

Some studies shown application of partial nitritation and anammox
processes for leachate treatment were potential control for nitrogen removal (Liang and Liu, 2007; Xiao et al., 2009; Xu et al., 2010;
Yapsakli et al., 2011). However, these processes only run at low
nitrogen loading rates in the previous studies and it ranged from
0.17 to 0.96 kg N/m3.d (Liang and Liu, 2008; Xu et al., 2010;
Rucalleda, 2011; Wang et al., 2011). Therefore, this study aimed to
evaluate the feasibility of the partial nitritation followed by
anammox process at high nitrogen loading rates for the old landfill
leachate treatment. A partial nitritation SBR and a hybrid anammox
reactor were used in this study.

is shown in Fig. 1. The PN-SBR is a cylindrical reactor with the
working volume of 66.5 L. Its size is 0.6 m high and 0.42 m in internal diameter. Air was supplied from the bottom of the PN-SBR
through five air diffusors, and the air flow was adjusted by a
manual valve to maintain the DO concentration higher than 3 mg/L.
The diluted feed raw leachate stored in 300 L tank, was pumped to
the PN-SBR. A mechanical stirrer at 30 rpm was used to enhance the
complete mixing with aeration. The supernatant decanted from
PN-SBR was stored in a container with volume of 90 L, and then it
was pumped to the HAR. The HAR was made of acrylic tube with an
internal diameter of 114 mm and the ratio of height to diameter is
5.7. Its working volume was 5 L. The HAR comprised suspended
biomass layer located in the bottom part, a spiral structure column
that was made from stainless steel in the middle part and a fixed
bio-carrier bed in the upper part. The spiral column consisted of 7
pitches to separate the nitrogen air from anammox sludge. The

distance between pitches was 4 cm, the length of whole spiral
column was 28 cm. Slope of each pitch was 300. The biomass carrier
consisted of 8 polyester non-woven porous sheets, which have a
total one-sided area of 1116 cm2, thickness of 0.5 cm and height of
31 cm (Japan Vilene, US patent 5,185,415, 1993). This carrier was
designed to enhance biomass attachment and to prevent the washout of biomass from the reactor. A gas collector was installed at top
of HAR.

2. Materials and methods

2.2. Experimental set-up and operational conditions

2.2.2. Enrichment of sludge
2.2.2.1. AOB sludge. The seed sludge was activated sludge from an
aeration tank of the Go Cat leachate treatment plant. An enrichment of AOB was conducted in PN-SBR. 546 g TSS of the seed sludge
was seeded into the reactor to obtain VSS concentration of
1500 mg/L. The ratio of VSS and TSS was 0.25. AOB sludge was
enriched using the leachate diluted with tap water to achieve
NH4eN concentration of 500 mg N/L. The PN-SBR run at DO higher
than 3 mg/L and HRT of 21 h for 45 days. Enrichment of AOB was
completed until the conversion efficiency of NH4eN to NO2eN
reached more than 90%. The effluent NO2eN and NO3eN concentration after enrichment were 486 mg N/L and 15 mg N/L,
respectively.

2.2.1. Experimental set-up
A lab-scale partial nitritation-anammox system including a PNSBR followed by HAR was used in this study. The schematic diagram

2.2.2.2. Anammox sludge. The HAR was inoculated with 9 g MLVSS
of anammox sludge, which was taken from the current polyester
non-woven carrier reactor (PNBCR) (Nhat et al., 2012). The

2.1. Feed leachate
Landfill leachate used in the study was collected from Go Cat
municipal solid waste landfill in Ho Chi Minh city, Vietnam, which
was closed in 2007. Its characteristics are shown in Table 1. Table 1
indicates that the typical characteristics of old landfill leachate
contained high NH4eN concentration and low BOD5:COD ratio
(Kjeldsen et al., 2002).
Feed leachate was diluted with tap water to obtain the influent
ammonia concentration ranging from 500 to 1000 mg N/L.

HAR (b)
Effluent

5

3
Influent

6

4

28 cm
20 cm

1

9 cm

Supernatant
tank ( 90 L)

28 cm

12 cm

7

8
2

31 cm

PN-SBR (a)

1

Sludge

(1)Influent pump; (2) feed raw leachate tank; (3) stirrer; (4) air pump; (5) gas collector;
(6) polyester non-wovenbiomasscarrier; (7)spiral column and (8) suspended anammox blanket.
Fig. 1. Schematic diagram of the lab-scale PN-SBR and HAR system.

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into PN-SBR effluent tank to reduce DO less than 0.5 mg/L. Amount

of 20 mg Na2SO3 was used to reduce about 1 mg DO. Influent pH
was adjusted in the range of 6.8e7.1 by HCl 20% solution. Operational conditions of the experiment show in Table 2.

Table 2
Operational conditions of PN-SBR and HAR system.
Time (days)

I

1ste45th

II

45the90th

HRT (h)

The influent TAN
concentration
(mg N/L)
500

1000

TAN loading rate
(kg/m3.d)

PN-SBR

HAR

PN-SBR

HAR

19
15
12
19
21

3

0.7
0.8
1.0
1.3
1.2

4.2

3

2.3. Analytical methods

8.3

dominant bacterial species in the consortium was identified as the
anammox Candidatus Kuenenia stuttgartiensis and uncultured anoxic
sludge bacterium KU2 (Nhat et al., 2012). The enriched anammox

biomass was adapted with synthetic wastewater (NH4Cl 215 mg N/
L, NaNO2 248 mg N/L, KHCO3 125 mg/L, KH2PO4 54 mg/L). Trace
element solutions were added based on the previous studies (Van
de Graff et al., 1996). The HAR run at the nitrogen loading rate of
8 kg N/m3/d during the enrichment of 60 days. The enrichment was
completed when the nitrogen the TN removal efficiency was above
90%, corresponding to the obtained removal rate (NRR) of 7.2 kg N/
m3/d. Then, the influent of HAR was switched to the effluent of PNSBR fed with the real leachate.
2.2.3. Operational conditions
2.2.3.1. Partial nitritation-Sequencing batch reactor (PN-SBR).
PN-SBR was operated with 10 min of feed, 45 min of settle and
5 min of decant. The adjustment of the aerobic reaction time of
reactor depended on the effluent NO-2eN to NHþ
4 -N ratio. HRT was
determined by the aerobic reaction time, total cycle time and volume exchange ratio. pH of the influent was controlled at 7.5 ± 0.2
by adding HCl 20% solution. DO in the reactor was maintained
higher than 3 mg/L. The study was operated at the influent total
ammonia concentration (influent TAN) of 500 and 1000 mg N/L.
The study aimed to determine a proper HRT of reactor at every
influent TAN concentration in order to obtain the suitable NO-2eN
to NHþ
4 eN ratio for anammox process. Operational conditions were
presented in Table 2.
2.2.3.2. Hybrid anammox reactor (HAR). The experiment was run
under dark condition by using a black plastic sheet enclosing fully
the reactor body to prevent algal growth. Na2SO3 salt was added

pH and DO were measured by using pH meter (HI 8314, Hanna)
and DO meter (InoLab 740 with terminal 740 WTW, Germany),
respectively. Total suspended solids (TSS), volatile suspended solids

(VSS), COD, NH4eN, NO2eN and NO3eN and alkalinity were
measured according to Standard Methods for examination of Water
and Wastewater (APHA, 1998). Sample filtration was done using
Whatman filter papers with pore size of 0.45 mm.
3. Results and discussion
3.1. Partial nitritation SBR (PN-SBR)
After 45 days of enrichment, NH4eN was converted to NO2eN
over 90% at the influent NH4eN concentration of 500 mg N/L and
HRT of 21 h. To get suitable influent for anammox process, the
partial nitritation should be run to reach to the stoichiometric
NO2eN:NH4eN ratio of 1.32. HRT of SBR was adjusted at values less
than 21 h (19 h, 15 h and 12 h). At HRT of 19 h, NO2eN: NH4eN ratio
was still high (2.75 ± 0.87, n ¼ 4) under steady-state condition. At
the loading rate of 0.7 kg TAN/m3.d, the mean effluent TAN and
NO2eN concentrations were 142 ± 35 mg N/L and 370 ± 28 mg N/L,
respectively. The ratio decreased to 1.53 ± 0.05 (n ¼ 6) at HRT of
15 h (NLR of 0.8 kg TAN/m3.d). The steady state condition reached
after 03 days of running at HRT of 12 h. The obtained NO2eN:
NH4eN ratio was 1.22 ± 0.1 (n ¼ 5) that was close to the stoichiometric ratio for anammox process. The mean effluent TAN and
NO2eN concentrations were 224 ± 9 and 274 ± 14 mg N/L,
respectively. In this phase, the effluent NO3eN concentration was
low (15 ± 2 mg N/L), equivalent to 3% of influent TAN. It means that
the partial nitritation which run at long HRT (15 h) and at NLR of
1.0 kg TAN/m3.d did not exist nitrate accumulation.
In phase II, the influent TAN concentration was increased to
1000 mg N/L. From 45th to 54th day, the NO2eN: NH4eN ratio was
low 0.67 ± 0.02 (n ¼ 4) at HRT 19 h (Fig. 2). It may be due to the
short HRT (19 h) coupled with high NLR (1.3 kg TAN/m3.d) that AOB
were not able to convert 50% of TAN to nitrite. As HRT increased up

4.0

Nitrogen Concentration (mg N/L)

1200
Phase II

Phase I

1000

3.0

2.75

800
600

1.53

400

2.0
1.22
1.02

1.0

NO2-N:NH4-N ratio

Phase

3

0.67

200

0.0

0
19
Inf N-NH4
Eff N-NO3

15
12
19
Nitrogen Loading Rate (kgN/m3.day)
Eff N-NH4
Eff NH4:NO2 ratio

21
Eff N-NO2
Stoichiometrical ratio

Fig. 2. Conversion of TAN and the effluent NO2eN to NH4eN ratio at the various HRTs in the PN-SBR experiment.

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Table 3 shows the biomass concentration and sludge retention
time in both phases. At NLR of 1.22 kg TAN/m3.d, the nitrogen
conversion rate of AOB was 0.53 kg TAN/kg MLVSS.d. It is found that
scum happened in Phase I (SRT of 20 days), whereas it insignificantly occurred in Phase II. The average effluent SS after 45 min of
settling was 19 ± 5 mg/L that shown a good settling ability of AOB at
SRT of 12 days.

Table 3
Biomass concentration and sludge retention time in the experiment.
Phase

SRT, days

SS, mg/L

MLSS, mg/L

MLVSS, mg/L

SVI, mL/g VSS

I

20 days

II

10e12 days

23 ± 3
(n ¼ 6)
19 ± 5
(n ¼ 13)

7712 ± 750
(n ¼ 6)
5583 ± 570
(n ¼ 7)

3479 ± 244
(n ¼ 6)
2298 ± 133
(n ¼ 7)

34 ± 2
(n ¼ 6)
43 ± 4
(n ¼ 7)

NLR, NRR kgN/m3.day)

to 21 h at NLR of 1.2 kg TAN/m3.d, NO2eN: NH4eN ratio of
1.02 ± 0.18 (n ¼ 12) was obtained. The effluent TAN and NO2eN
concentrations were 469 ± 58 mg N/L and 516 ± 40 mg N/L,
respectively. The effluent NO3eN concentration was low (20 ± 7)

mg N/L. The result of this study was similar to that of Taichi
Yamamoto et al. (2008), who used successfully partial nitritation
reactor for swine wastewater digester liquor at TAN loading rate of
1.0 kg N/m3.d.
With the above result, it is expected that PN-SBR may run
effectively at higher influent TAN concentration at longer HRT and
at NLR which should be kept by 1.2 kg TAN/m3.d. However, increase
of influent TAN concentration may result in rise of free ammonia
(FA) in SBR as well as rise of alkalinity demand as carbon sources for
AOB. Some previous studies claimed that nitritation process
running at the NLRs over 1 kg TAN/m3.d was inhibited AOB growth
at FA concentration of about 150 mg N/L (Anthonisen et al., 1976;
 et al., 2012). In this study, the
Kurniawan et al., 2006; Ganigue
average FA concentration in the PN-SBR was less than 20 mg N/L
that did not inhibited AOB.

10.0

3.2. Hybrid anammox reactor (HAR)
In enrichment, the HAR was run with the synthetic wastewater
at 8.0 kg TN/m3.d. After two months, the obtained TN removal rate
was 7.9 kg TN/m3/d. The HAR was then run with the effluent from
PN-SBR. High nitrogen removal rate (3.6 kg TN/m3/d) was obtained
at NLR of 4.0 kg TN/m3.d after 45 days of run. This presented that
the components of the leachate with TN of 500 mg N/L from PNSBR did not cause negative impact on anammox bacteria. Fig. 3a,b
shows the time courses of TN (TAN þ NO2eN) removal efficiency
and TN removal rate of the HAR during 90 days of experiment. The
obtained TN removals were 93 ± 1% and 81 ± 1.2% at NLRs of
4.3 kg TN/m3.d (phase I) and 8.3 kg TN/m3.d (phase II), respectively.

At NLR of 4.0 kg N/m3.d, the effluent TAN, NO2eN, and NO3eN of
HAR were 9.7 ± 3.5 mg N/L, 1.7 ± 0.4 mg N/L and 23 ± 4 mg N/L,
respectively. This effluent quality was good enough to meet QCVN
25:2009/BTNMT.
At NLR of 8.3 kg N/m3.d (HRT of 3 h and influent TN concentration of 1000 mg N/L), the effluent TAN, NO2eN, NO3eN and TN

Phase II

Phase I

8.0

6.0
4.0
NLR

2.0

NRR

0.0

(a)
Nitrogen concentration (mg N/L)

1200
1000

Phase II

Phase I
800
600
400
200
0

1

6

12

18

24

30

36

42

48

54

60

66

81

90

Operating time (day)
Inf TAN (PNSBR)
Eff NO3 (PNSBR)
Eff NO3 (HAR)

Eff NH4 (PNSBR)
Eff NH4 (PNSBR)

Eff NO2 (PNSBR)
Eff NO2 (HAR)

(b)
Fig. 3. Time courses of the whole system: (a) Nitrogen loading rate (NLR) and nitrogen removal rate (NRR); (b) Nitrogen concentration.

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Ammonia removal (%)

concentrations were 76 ± 11 mg N/L, 80 ± 9 mg N/L, 39 ± 5 mg N/L
and 196 ± 12 mg N/L, respectively. This effluent quality was not met
threshold values of the leachate quality standards. It is expected
that the effluent nitrogen concentration may reach the QCVN

25:2009/BTNMT as the HAR is run at lower NLR, corresponding to
longer HRT.
The produced NO3eN was about 10% of influent TN in anammox
process (Furukawa et al., 2009). In the anammox process, the
stoichiometric ratio of NH4eN and NO2eN consumption and the
NO3eN production (molar NH4:NO2:NO3 ratio) is 1:1.32:0.26
(Strous et al., 1998). The obtained molar NH4:NO2:NO3 ratios in this
study were 1:1.27:0.03 at phase 1and 1:1.13:0.05 at phase 2. The
different ratios were reported by some previous researches on
leachate treatment. The study of Ruscalleda (2011) and Liang and
Liu (2008) presented the ratio of 1: 1:42: 0:15 and 1:1.09: 0.007,
respectively. The significant difference between the obtained ratios
in this study and the stoichiometric value is nitrate production. This
may be due to the presence of heterotrophic denitrifying bacteria in
the HAR. Indeed, nitrate reduction coupled with COD removal was
found during all the operational periods.
Liang and Liu (2008) who used an up-flow fixed bed annamox
biofilm reactor for old landfill leachate treatment shown that the
obtained NRR was 0.2 kg N/m3.d at TN concentrations of
1000e1500 mg N/L. The research of Furukawa et al. (2009) got NRR
of 4.2 kg N/m3.d for a PEG gel carrier anammox reactor used to treat
anaerobic swine wastewater digester liquor at NLR of 5.3 kg N/m3.d.
In comparison with the above researches, an extremely high NRR
(7.3 kg N/m3.d) at NLR of 8.3 kg N/m3.d was achieved in this study.

100
90
80
70
60

50
40
30
20
10
0

Biomass concentration increased from 9000 mg/L at the
beginning of enrichment to 28,960 ± 980 mg MLSS/L and
20,400 ± 1000 mg MLVSS/L at the end of the experiment. The
maximum total nitrogen removal rate of anamnox biomass was
0.4 kg TN/kgVSS.d. The average effluent SS during the phase II was
10 ± 6 mg/L. This presents the sludge wash-out was not remarkably
during the experiment. It is explained that the combination between suspended growth using a spiral column and the bio-carrier
enhanced the sludge wash-out.
Figs. 4a and b presents the TAN conversion of PN-SBR, HAR and
TN removal of the whole system. The ammonia removal of the
overall system depended much on ammonia conversion of PN-SBR.
In phase I, the ammonia removal of 99 ± 1% in the overall system
was achieved when conversion of NH4eN of PN-SBR was 61 ± 8%.
Whereas, in phase II, the ammonia removal (91 ± 3%) and conversion to nitrite (49 ± 6%) of the whole system were little bit lower.
Fig. 4b shows that the TN removal efficiency was 85 ± 7% and
81 ± 1% in Phase I and Phase II, respectively. The highest TN removal
of the whole system was reached at the end of the phase I when the
molar NH4:NO2 ratio of PN-SBR was 1.22. Thus, control of molar
NH4:NO2 ratio of PN-SBR is very important to aim to high TN
removal efficiency of the overall system.
3.2.1. COD Removal
Fig. 5 shows the removal of COD of overall system during 100
days of experiment. The COD removal efficiency of overall system in

phase I and II were 50 ± 3% and 46 ± 12%, respectively. The COD
removal by PN-SBR was low, it was only 18 ± 4% in phase I and

Phase I

1

6

12

18

5

Phase II

24 30
HAR

36

42

48 54 60
PN-SBR

66

81

90

Operation time (day)

TN removal (%)

(a)
100
95
90
85
80
75
70
65
60
55
50

Phase II

Phase I

1

6

12

18

24

30

36

42

48

54

60

66

81

90

Operating time (day)

(b)
Fig. 4. Time course of nitrogen removal of PN-SBR and HAR system experiment: (a) Ammonia; (b) TN (TAN þ NO-2eN þ NO-3eN).

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Inf COD (PNSBR)

Eff COD (PNSBR)

Eff COD (HAR)

COD Concen. (mg/L)

1200
Phase I

1000

Phase II

800
600
400
200
0
1

6 12 18 24 30 36 39 42 48 54 60 63 66 69 72 75 78 81 84 87 90
Time course (day)
Fig. 5. Removal of COD in the PN-SBR and HAR system.

12 ± 5% in phase II. It is due to low ratio of BOD5 to COD in the raw
leachate (around 0.1). The average BOD5 of leachate (425 ± 72 mg
BOD5/L) was 12% of total COD. BOD5 content was completely
removed in the PN-SBR. The result is similar to that of the study of
Wang et al. (2014) which presented the low COD removal (30%) and
high BOD5 removal (80%) in the PN-SBR.
The COD removal of the HAR ranged from 14 to 46%, whereas
biodegradable COD were fully removed in the PN-SBR. Similarly,
Liang and Liu (2008) reported that old landfill leachate treatment
using anammox reactor obtained COD removal of 23e41%. Bacterial
community of the HAR may remove refractory organics such as
fulvic-like compounds from the PN-SBR effluent. Denitrifying bacteria could not directly use aquatic humic substance (AHS) in the
leachate. Liang and Liu (2008) indicated that some kinds of heterotrophs living in community of annamox biomass were able to
degrade AHS into readily biodegradable organic matters which
were then utilized by denitrifier living in the community.
4. Conclusions
The system including a PN-SBR followed by a HAR was able to
remove efficiently total nitrogen from the old landfill leachate. The
effluent quality was met the Vietnamese leachate quality standards at NLR of 1.0 kg TAN/m3/d for PN-SBR and 4.0 kg TN/m3.d for
HAR. The HAR obtained the extremely high NRR of 7.3 kg TN/m3/
day at NLR of 8.3 kg TN/m3/day. The achievement of molar
NH4:NO2 ratio of 1.2e1.4 for PN-SBR helped to enhance TN rem
oval efficiency of the overall system. Bacterial community of HAR
was able to degrade slowly biodegradable or non-biodegradable
COD.
Acknowledgments
The Authors gratefully thank to Vietnam Brewery Ltd. Company
for financial support of this study.
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