Modified Operation in SBR Applied to Decentralized ... · technologies, such as CASS (cyclic...

1 L. J. Yuan et al. / Journal of Water Sustainability 3 (2011) 1-10

* Corresponding to: [email protected]

Modified Operation in SBR Applied to Decentralized Domestic

Sewage Treatment for High Quality Effluent

Lin Jiang Yuan1*

, Jie Zhao1, Kai Yang

1, Zhi Ying Wang

1

1School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, Xi’an,

710055, China

ABSTRACT

SBR can be used as the sole reactor for SS, COD, and nutrient removal and is suitable for decentralized wastewater

treatment, but it is noticed that the SBR is difficult to obtain high quality effluent meeting up to Grade 1A standard

in China in many practical cases. In this study sewage from a university campus was used as decentralized sewage,

and its treatment of SBR was investigated. Two operating modes were adopted to study whether SBR can serve as

sewage treatment with high quality effluent that may meet the standard of water reuse to some extent. The results

show that, after changing anaerobic and aerobic stage, the SBR can remove as more as 90%, 92%, 67% and 89% of

COD, ammonium nitrogen, total nitrogen and phosphate of the sewage, respectively, and effluent meet water

quality for reuse. Proper alternation of anoxic condition (lasting for 30min before feeding), anaerobic condition

followed (lasting 1h after feeding) and aerobic condition (for 2h with low dissolved oxygen less than 2mg/l all the

way) is the foundation for effluent of good quality and stable operation. The results suggest that the SBR performed

very well to treat sewage of low carbon to nitrogen ration and large fluctuation in water quality, and it is suitable for

decentralized wastewater treatment and water reclamation. Operation control of the SBR can not only save energy,

but also can dispense with advanced water treatment of water reclamation to some extent.

Keywords: Decentralized wastewater treatment; SBR; Water reclamation; Biological nutrient removal

1 INTRODUCTION

With increasing attention on water pollution

control in China, treatment of wastewater

discharged from area out of service of urban

centralized drainage system, i.e. decentralized

wastewater, becomes more and more urgent.

Decentralized wastewater has some distin-

guished differences from common municipal

wastewater. For example, it is small in quan-

tity in most cases. The quantity maybe varies

from several cubic meters to hundreds. The

figure may be thousands in some residential

areas and towns and villages. Secondly, there

is large fluctuation in both wastewater quanti-

ty and quality (Bian and Yuan, 2009). Due to

obvious relevancy and high consistent with

work and rest of residual in water used and

discharge, both wastewater quantity and

quality vary greatly with time throughout the

day. Sometimes they are intermittent. There

hardly has sewage discharged by community

in midnight and from university campus in

vacation. Finally, the strength of decentralized

wastewater is usually lower compared with

municipal wastewater, especially in carbon to

nitrogen ratio (Ma et al., 2009).

In many cases of decentralized wastewater

treatment, there are lack of professional

Journal of Water Sustainability, Volume 1, Issue 3, December 2011, 259-268

© University of Technology Sydney & Xi’an University of Architecture and Technology

DELL

打字机文本

DOI: 10.11912/jws.1.3.259-268


operator and manager who are absolutely

necessary in big municipal wastewater treat-

ment plant. Complicated treatment process,

high capital cost and operation cost may not

be acceptable in addition. Under these cir-

cumstances, treatment of low cost and simple

process is welcome (Massoud et al., 2009).

Many designers are apt to adopt SBR (se-

quencing batch reactor) and its derivative

technologies, such as CASS (cyclic activated

sludge system) in decentralized wastewater

treatment (Ng et al., 1993; Bernardes and

Klapwijk, 1996; Kassaba et al., 2011). Based

on investigation of performances of a few

decentralized wastewater treatment facilities

located in Xi’an city, China, it has been found

that most of their performances are not stable

and their effluents cannot meet discharge

standard required (class 1B of GB 18918

-2002). It is considered that proper operating

strategy is the foundation of satisfying effluent.

How to deal the conflicts among COD,

nitrogen and phosphorus removal in the

unique tank of SBR still needs to study.

If advanced treatment is applied after sec-

ondary treatment of decentralized wastewater

to reclaim water, this process will lose ad-

vantage. In another scenario, if the effluent

from common secondary treatment in the SBR

is of high quality that can be served as recla-

mation water after filtration (if necessary) and

disinfection for landscape water supply and

green sprinkle, it will be appealing in practice.

A SBR was applied in this study to treat the

sewage discharged from a university campus

as decentralized wastewater. Key operation

parameters and mode for secondary treatment

for high quality effluent was studied in order

to find out a solution for decentralized

wastewater treatment and reuse.

2 MATERIALS AND METHODS

2.1 Experiment Setup

The experiment setup is illustrated in Figure 1.

Reactor was a plexiglas tank with 250-liter

effective working volume. Size of the tank is

92 ×60 ×55 cm (L×B×H) and water depth is

less than 50 cm. 4 perforated tubes fixed on

the bottom of the tank were applied as oxygen

diffuser. Air supply rate was controlled via air

flow meter. 2 stirrers were applied to mix liq-

uid in the tank when there was no aeration.

2.2 Wastewater and Inoculation Sludge

Raw sewage from drainage of campus of a

university in Xi’an city was applied. Water

quality of the sewage is shown in Table 1.

Activated sludge from A2O system of Deng

Jia Cun municipal wastewater treatment plant

was inoculated, and its concentration in the

reactor was about 2200 mg/L (MLVSS) with

SVI of 180 L/g.

2.3 Operating Procedures of the System

Reactor was operated 4 cycles (6 h per cycle)

per day. Two operating modes were adopted,

namely Run 1 and Run 2. The system was

operated under Run 1 for 60 days and Run 2

for 120 days. Operating procedure of Run 1

was as follows: feeding with stirring for 0.5 h-

anaerobic mixing for 1h- aeration for 2 h-

anoxic mixing for 1h- aeration for 0.5 h-

precipitation for 55 min- drawing for 5 min

(i.e. Ana-O-Ano-O mode).

Table 1 Quality of the sewage

item CODcr SS PO43-

-P NH4-N TP TN

Conc. (mg/L) 132~320 122~455 1.2~6.9 15~35 1.5~7.8 35~60

L. J. Yuan et al. / Journal of Water Sustainability 3 (2011) 259-268 261

1

2

3

4

5

6 8

4 4

7

5

7 7

9

Figure 1 Schematic diagram of the experiment system (1. drainage pipeline; 2.feeding pump;

3. processor; 4. air pump; 5. mixer; 6. SBR reactor; 7. perforated tube; 8. drawing

pump; 9. DO meter)

In Run 2, operating procedure was mixing for

0.5 h before feeding, and then feeding with

stirring for 0.5 h. Anaerobic mixing for 1h-

aeration for 2h- precipitation for 1h- drawing

for 5 min- idle for 55min (i.e. pre-Ano–Ana-

O mode) (Table 2). Temperature in the reactor

was at 27~33˚C during the experiment. SRT

maintained at 15 d. Volume changing ratio

was 50% in one cycle. DO was maintained at

2-4 mg/L in the aerobic phase in Run 1 and

0-1.5 mg/L in Run 2.

2.4 Analysis Methods

The concentrations of COD, ammonium, ni-

trate, total nitrogen, phosphate, and total phos-

phorus were determined following the me-

thods set out in the standard methods (China

EPA, 2002). COD was determined by dichro-

mate method, ammonia by Nessler’s reagent

colorimetric method, nitrates by ultraviolet

spectrophotometric method, total nitrogen by

potassium persulfate digestion- UV Spectro-

photometric method, phosphate by ammonium

molybdate spectrophotometric method, and

total phosphorus by potassium persulfate

digestion- ammonium molybdate spectropho-

tometric method.

3 RESULTS AND DISCUSSION

3.1 Performance of the System Operated

in Run 1

Performance of the system operated in Run 1

is shown in Figure 2. As shown in Figure 2a to

2e, average removal rates of the system for

COD, ammonium nitrogen, phosphate, total

nitrogen and suspended solids are about 90%,

97%, 93%, 67% and 95%, respectively. The

average concentrations of COD, ammonium

nitrogen, phosphate, total nitrogen and sus-

pended solids in effluent are about 32, 0.71,

0.21, 14.63 and 12.45 mg/L, respectively.

Table 2 Operating modes in a cycle of Run 1 and Run 2

Period 0.5h 0.5h 0.5h 0.5h 0.5h 0.5h 0.5h 0.5h 0.5h 0.5h 0.5h 0.5h

Run 1 F & S Ana Oxic Anoxic Oxic P & D

Run 2 S F & S Ana Oxic P D & Idle

Note: F-feed, S-stirring, P-precipitation, D-drawing, Ana-anaerobic.


0

100

200

300

400

500

600

0 5 10 15 20 25 30 35 40 45 50 55 60

Time (d)

CO

D (

mg/L

)

0

20

40

60

80

100

Rem

oval

rat

e (%

)

inf eff Removal rate

0

1

2

3

4

0 5 10 15 20 25 30 35 40 45 50 55 60

Time (d)

P (

mg

/L)

0

20

40

60

80

100

Rem

ov

al r

ate

(%)


0

10

20

30

40

0 5 10 15 20 25 30 35 40 45 50 55 60

Time (d)

NH

4-N

(m

g/L

)

0

20

40

60

80

100

Rem

oval

rat

e (%

)

eff inf Removal rate

As a whole, the system performed well on

removing of ammonium, but not very well on

its removal of total nitrogen and phosphate.

Figure 2a

Figure 2b

Figure 2c


0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45 50 55 60

Time (d)

TN

(m

g/L

)

0

20

40

60

80

100

Rem

oval

rat

e (%

)

inf inf Removal rate

0

100

200

300

400

500

0 5 10 15 20 25 30 35 40 45 50 55 60

Time (d)

SS

(m

g/L

)

0

20

40

60

80

100

Rem

oval

rat

e (%

)


Figure 2d

Figure 2e

Figure 2 Performance of the system operated in Run 1

CC

OD

0

10

20

30

40

50

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 6

0

100

200

300

400

500

P NH4-N NO3-N TN COD

fill Ana Oxic Anox Draw Oxic

CO

D (

mg

/L)

NH

4-N

, N

O3-N

, T

N,

P (

mg

/L)

Time (h)

Figure 3 The profiles of ammonium phosphorus, nitrate, total nitrogen and COD in a typical

cycle in Run 1


0

100

200

300

400

500

600

0 20 40 60 80 100 120Time (d)

CO

D (

mg/L

)

0

20

40

60

80

100

Rem

oval

rat

e (

%)


0

1

2

3

4

0 20 40 60 80 100 120

Time (d)

P (

mg

/L)

0

20

40

60

80

100

Rem

oval

rat

e (

%)


Figure 3 shows the profiles of ammonium,

phosphorus, nitrate, total nitrogen and COD

in a typical cycle in Run 1. As shown in the

figure, the lower removal for nitrite and total

nitrogen is considered to be due to scarce of

carbon source in anoxic stage where denitri-

fication occurred.

3.2 Performance of the System Operated

in Run 2

To improve the removal ability of the total

nitrogen and phosphate, operating mode of

the system was changed into mode 2, i.e.,

Run 2. The performance of the system in Run

2 is shown in Figure 4.

As shown in Figure 4a to 4e, average re-

moval rates of the system for COD, ammo-

nium nitrogen, phosphate, total nitrogen and

suspended solids are about 93%, 93%, 96%,

75% and 95%, respectively. The average

concentrations of COD, ammonium nitrogen,

phosphate, total nitrogen and suspended

solids in effluent are about 27.4, 2.1, 0.07,

11.7 and 10.6 mg/L, respectively. The system

performed better on removing of total nitro-

gen and phosphate ammonium compared with

that of Run 1. What is more attractive, Run 2

has a lower energy cost in aeration due to

control lower concentration in aerobic stage

and shorter aeration period. But That it

resulted in a little higher concentration of

ammonium in effluent of Run 2 of about 2.1

mg/L (average) should be noticed.

Figure 4a

Figure 4b


0

10

20

30

40

0 20 40 60 80 100 120

Time (d)

NH

4-N

(m

g/L

)

0

20

40

60

80

100

Rem

oval

rat

e (%

)

eff inf Removal rate

0

10

20

30

40

50

60

0 20 40 60 80 100 120

Time (d)

TN

(m

g/L

)

0

20

40

60

80

100

Rem

oval

rat

e (%

)

inf inf Removal rate

0

100

200

300

400

500

0 20 40 60 80 100 120

Time (d)

SS

(m

g/L

)

0

20

40

60

80

100

Rem

ov

al r

ate

(%)


Figure 4c

Figure 4d

Figure 4e

Figure 4 Performance of the system operated in Run 2


0

5

10

15

20

25

0 0.5 1 1.5 2 2.5 3 3.5 4 5

Time（h）

NH

4-N、

NO

3-N、

TN、

P(m

g/L

)

0

10

20

30

40

50

CO

D（

mg

/L）

P NH4-N TN NO3-N COD

Feed AnaOxic Drawn

Pre-

anoxic

Figure 5 The profiles of ammonium, phosphorus, nitrate, total nitrogen and COD in a typical

cycle in Run 2

Figure 5 shows the profiles of ammonium,

phosphorus, nitrate, total nitrogen and COD in

a typical cycle in Run 2. As shown in the

figure, because of 30 min of pre-anoxic

stirring before feeding the system, total

nitrogen and nitrate were removed thoroughly

that improved the anaerobic phosphorus

release in anaerobic stage followed.

3.3 Discussion

It is commonly accepted that biological

nitrogen removal conflicts with biological

enhanced phosphorus removal due to compe-

tition for carbon source and different condi-

tion needed (Kuba et al., 1996; Third et al.,

2003; Yuan et al., 2007). High effective

biological nutrient removal in SBR will be

more difficult due to unique tank. In order to

remove nitrogen and phosphate in decentral-

ized domestic sewage, alternating operation

condition is indispensable (Pochana and

Keller, 1999; Zhao et al., 1999).

From the results of this study, it is indicated

that the system could achieve good perfor-

mance on both nitrogen and phosphate re-

moval operated in the two modes. There is

hardly difference between the operations in

Run 1 and Run 2 in removals of COD, SS,

ammonium, total nitrogen and phosphate. It is

suggested that the operating strategies of the

system were proper. In Run 1, the removal of

ammonium is more effective than that of

Run2, but it is reverse for total nitrogen and

phosphate removal. The reason for high

efficient removal of total nitrogen and phos-

phate achieved in Run 2 is considered as that

pre-anoxic stage before feeding greatly

benefited phosphate release of PAOs in

anaerobic stage followed and simultaneously

organic substance oxidization, nitrification,

denitrification with excessive phosphate

uptake in oxic stage whit DO of less than 1.5

mg/L (DO was almost null within the first 30

min, and in the 30 min followed, DO was less

than 1 mg/L, finally it increased to not more

than 1.5 mg/L).

Concentrations of COD, TN, ammonium

nitrogen and phosphate in the effluents in the

two operation modes are less than 50, 15, 5,

and 5 mg/L, respectively. Qualities of the

effluents of the reactor operated under both

modes even met the Standard for Pollutants

Discharged from Municipal Wastewater

Treatment Plant (GB18919-2002) of 1A class,

only SS of 12.45 and 10.63 mg/L in average

in mode1 and 2, respectively, is slightly

higher than the standard limitation of 10 mg/L.

The effluents basically meet reclaimed water

quality applied for miscellaneous usage in


case of less requirements of SS. Otherwise,

simple coagulation/ filtration applied can

make SS in the effluents meet usage of more

stringent requirements for reclaimed water. It

is suggested that the treatment achieved

wastewater treatment and water reclamation

simultaneously.

From Figures 2 and 4, it can be seen that

the influent of the system fluctuated very

obviously in quality, but the effluent was very

stable. It implies that the treatment of the SBR

has a good capacity for water quality fluctua-

tion, which suitable for decentralized

wastewater treatment. It is found that after

feeding, COD to TN ratio in the reactor is 4:1

to 2:1, that means organic substance in the

influent is not enough for nitrogen and phos-

phate removal (Narkisa, 1979; Chiu and

Chung, 2003). As discussed above, by appli-

cation of DO control strategy in aerobic stage,

simultaneous nitrification and denitrification

as well as denitrifying phosphorus accumula-

tion of PAOs occurred (Figure 5), and as a

result organic substance needed for nitrogen

and phosphate removal was saved. It is

demonstrated proper operation strategy set is

basic for good effluent of the SBR.

CONCLUSIONS

Both Ana-O-Ano-O mode and pre-Ano-Ana

-O mode can achieve effluents of good quality

that may satisfy reuse purpose to some extent.

Mode 2 with lower operation cost and simpler

operation is more appealing for application.

The SBR is adequate to decentralized domes-

tic wastewater treatment with high quality

effluent. Proper operation strategy is basic for

good effluent.

ACKNOWLEDGEMENT

This research was supported by National Key

Science and Technology Projects on Water

Pollution Control and Management (Grant NO.

2009ZX07212-002-004-002, 2009ZX07212-0

02-004-003), National Natural Science Foun-

dation of China (Grant NO. 50878180,

51078304), and EU-China River Basin Man-

agement Program.

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