序批式反应器处理工业废水的牛奶生物膜系统4321

序批式反应器处理工业废水的牛奶生物膜系统

Sequencing batch reactor biofilm system for treatment of milk industry wastewater

Suntud Sirianuntapiboona,*, Narumon Jeeyachokb, Rarintorn Larplaia

aDivision of Environmental Technology, School of Energy and Materials, King Mongkut’s University of Technology Thonburi (KMUTT),

Thungkru, Bangmod, Bangkok 10140, Thailand

bDivision of Biochemical Technology, School of Bioresources and Technology, King Mongkut’s University of Technology Thonburi,

Thungkru, Bangmod, Bangkok 10140, Thailand

Received 22 October 2003; revised 27 November 2004; accepted 19 January 2005

Available online 21 April 2005

Abstract

A sequencing batch reactor biofilm (MSBR) system was modified from the conventional sequencing batch reactor (SBR) system by

installing 2.7 m2 surface area of plastic media on the bottom of the reactor to increase the system efficiency and bio-sludge quality by

increasing the bio-sludge in the system. The COD, BOD5, total kjeldahl nitrogen (TKN) and oil & grease removal efficiencies of the MSBR

system, under a high organic loading of 1340 g BOD5/m3 d, were 89.3G0.1, 83.0G0.2, 59.4G0.8, and 82.4G0.4%, respectively, while they

were only 87.0G0.2, 79.9G0.3, 48.7G1.7 and 79.3G10%, respectively, in the conventional SBR system. The amount of excess bio-sludge

in the MSBR system was about 3 times lower than that in the conventional SBR system. The sludge volume index (SVI) of the MSBR system

was lower than 100 ml/g under an organic loading of up to 1340 g BOD5/m3 d. However, the MSBR under an organic loading

of 680 g BOD5/m3 d gave the highest COD, BOD5, TKN and oil & grease removal efficiencies of 97.9G0.0, 97.9G0.1, 79.3G1.0 and

94.8G0.5%, respectively, without any excess bio-sludge waste. The SVI of suspended bio-sludge in the MSBR system was only

44G3.4 ml/g under an organic loading of 680 g BOD5/m3 d.

Keywords: Sequencing batch reactor (SBR); Bio-film; Milk industry wastewater; Excess bio-sludge

1. Introduction

The annually increasing milk consumption in Thailand

has demanded an increase in milk production resulting in an

increasing amount of industrial wastewater (Department of

Industrial Works, 2001, Information center). Milk industry

wastewater contains high concentrations of COD, BOD5

and TKN of up to 11,000, 5900 and 720 mg/l, respectively

(Viraraghavan, 1994; Department of Industrial Works,

2001). Several biological treatment systems have been

used such as the activated sludge system, anaerobic pond,

oxidation pond, trickling filter, and the combined trickling

filter and activated sludge system (Department of Industrial

Works, 2001; Garrido et al., 2001; Irvine and Busch, 1979;

Perle et al., 1995). However, each system had disadvantages

(Ince, 1998; Metcalf & Eddy, 1991; Rusten et al., 1993).

The aerated lagoon required a greater area and the effluent

quality fluctuated (Metcalf & Eddy, 1991; Department of

Industrial Works, 2001). The anaerobic pond produced a

bad smell caused by H2S and NH3 (Ince, 1998; Metcalf &

Eddy, 1991). The activated sludge system was also selected

to treat milk industry wastewater due to its high removal

efficiency (Garrido et al., 2001; Zayed and Winter, 1998),

but it consumed a high amount of energy and the biosludge

was often raised and bulked in the clarifier

(Sirianuntapiboon and Tondee, 2000; Cecen and Orak,

1996; Metcalf & Eddy, 1991). The SBR system might be

suitable to treat milk industry wastewater because of its

ability to reduce nitrogen compounds by nitrification and

denitrification (Sirianuntapiboon, 2000; Metcalf & Eddy,

1991; Keller et al., 1997), but the SBR system still has some

disadvantages such as the high excess sludge produced and

the high sludge volume index (Barnett et al., 1994; Bernet et

al., 2000; Kagi and Uygur, 2002; Wilen and Balmer, 1998).

Journal of Environmental Management 76 (2005) 177–183

www.elsevier.com/locate/jenvman

doi:10.1016/j.jenvman.2005.01.018

* Corresponding author. Tel.: C66 2 4708602; fax: C66 2

4279062/4708660.

E-mail address: [email protected] (S. Sirianuntapiboon).

In this study, an attached growth system was applied in

the conventional SBR reactor by installing plastic media on

the bottom of the SBR reactor to increase the system

efficiency, bio-sludge quality and to reduce the excess

bio-sludge. The experiments were carried out in both SBR

and MSBR systems to observe the phenomena of

the systems and the removal efficiencies and quality of the

bio-sludge.

2. Materials and methods

2.1. Laboratory wastewater treatment units

Two types of sequencing batch reactor (SBR) systems

were used in this study, the conventional SBR system and

the MSBR system as shown in Fig. 1. For the MSBR system,

plastic media with a total surface area of 2.7 m2 (Fig. 2,

Table 1) was installed on the bottom of the reactor. Both the

MSBR and the SBR reactors (each of 25 l capacity) were

made from acrylic plastic (5 mm thick). The dimensions of

each reactor were 0.29 m (diameter) by 0.35 m (height), the

working volume being 20 l. A low speed gear motor, model

P 630A-387, 100 V, 50/60 Hz, 1.7/1.3 A (Japan Servo Co.

Ltd, Japan), was used for driving the paddle-shaped

impeller. The speed of the impeller was adjusted to

60 rpm. One set of air pumps, model EK-8000, 6.0 W

(President Co. Ltd, Thailand), was used for supplying air for

two sets of reactors.

2.2. Milk industrial wastewater (MIWW)

MIWW collected from a milk factory in Bang-pa-in

industrial estate, Ayuthaya province, Thailand was used in

this study. The factory produced mainly pasteurized milk

and UHT milk products. The wastewater samples were

Fig. 1. MSRB and SBR systems.

Fig. 2. Shape of plastic media in MSBR reactor.

178 S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177–183 collected from the sump tank of the wastewater treatment

plant once/day for 1 week to determine the chemical

properties. The chemical properties of the wastewater are

shown in Table 2.

2.3. Acclimatization of bio-sludge for MSBR

and SBR systems

Bio-sludge from the bio-sludge storage tank of the

central sewage treatment plant of Bangkok city (Sriphaya

plant) was used as the inoculum for both the SBR and

MSBR systems after being acclimatized with milk industrial

wastewater for 1 week.

2.4. Operation of SBR system

The operation program of the SBR system consisted

of five steps: fill, react (aeration), settle (sedimentation/clarification), draw (decant) and idle (Metcalf & Eddy, 1991)

3.5 l of 10 g/l acclimatized bio-sludge was inoculated in

each reactor of both the SBR and MSBR systems, and

MIWW was added (final volume of 20 l) within 2 h

(fill step). During the feeding of MIWW, the system had

to be fully aerated. The aeration was then continued for

another 19 h. (react step: aeration). Aeration was then shut

down for 3 h (settle step: sedimentation/clarification). After

the bio-sludge was fully settled, the supernatant had to be

removed (the removed volume of the supernatant was based

on the operation program as mentioned in Table 3) within

0.5 hr (draw step: decant) and the system had to be kept

under anoxic conditions (idle step) for 0.5 h. After that,

fresh MIWW was filled into the reactor to the final volume

of 20 l and the above operation program was repeated. For

the removal of excess bio-sludge to control the stable

bio-sludge concentration of the reactor, the excess biosludge

was wasted from the bottom of the reactor (Fig. 1)

during the idle step. In each operation condition as shown in

Table 3, the reactor was operated for 30 d.

2.5. Chemical analysis

The biochemical oxygen demand (BOD5), chemical

oxygen demand (COD), suspended solids (SS) total kjeldahl

nitrogen (TKN), oil & grease, total phosphorus (TP) and pH

of influents and effluents, mixed-liquor suspended solids

(MLSS), excess sludge, and sludge volume index (SVI)

were determined by using standard methods for the

examination of water and wastewater (APHA, AWWA

and WPCF, 1995). The bio-film on the media was removed

by washing with an acetate buffer (pH 7.0). The washed

bio-film in the solution was then determined as the bio-film

mass (APHA, AWWA and WPCF, 1995). Solid retention

time (SRT), or sludge age, was determined by measuring the

average residence time of the suspended microorganisms

(suspended bio-sludge) in the system. F/M was presented as

a ratio of BOD5 loading and the total bio-sludge of the

system.

Table 1

Properties of the media

Properties Value

Size of each media, cylindrical shape 5 cm in diameter and

1.25 cm in high

Volume of each media 2.50 cm3

Surface area of each media 0.03 m2

Weight of each media 2.40 g

Density of each media 0.96 g/cm3

Number of media in each MSBR reactor 90 pieces

Total surface area of media in each MSBR

reactor

2.7 m2

Total volume of media in each MSBR reactor 225 cm3

Total weight of media in each MSBR reactor 220.5 g

Table 2

Chemical compositions of milk industrial wastewater

Chemical

compositions

Range AverageGSD

COD (mg/l) 5000–10,000 7500G324

BOD5 (mg/l) 3000–5000 4000G59

TS (mg/l) 3000–7000 5000G46

Oil & grease (mg/l) 70–500 200G7.3

TKN (mg/l) 50–150 120G2.8

TP (mg/l) 50–70 60G0.41

pH 4.0–7.0 6.0G0.62

Temperature (8C) 34–35 34.5G0.47

Table 3

Operation parameters of SBR and MSBR systems

Parameters HRT (d)

3 4 6 8

Working volume of

reactor (l)

20 20 20 20

Flow rate (l/d) 6.7 5.0 3.4 2.5

Replacement

volume (l/d)

6.7G0.3 5.0G0.3 3.4G0.2 2.5G0.1

Operating cycle

(times/d)

1 1 1 1

Operating step (h) 24 24 24 24

Fill up (h) 2.0 2.0 2.0 2.0

Aeration (h) 19.0 19.0 19.0 19.0

Settling (h) 1.5 1.5 1.5 1.5

Draw & Idle (h) 1.5 1.5 1.5 1.5

Hydraulic loading

(m3/m3 d)

0.34 0.25 0.17 0.13

Hydraulic loading

(m3/m2 d)a

0.0025 0.0019 0.0012 0.0009

Volumetric organic

(g BOD5/m3 d)

1340 1000 680 500

Surface area-organic

(g BOD5/m2 d)a

993 741 504 370

a They were used for the MSBR system.

S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177–183 179

2.6. Statistical analyze method

Each experiment was repeated at least 3 times. All the

data were subjected to two-way analysis of variance

(ANOVA) using SAS Windows Version 6.12 (SAS

Institute, 1996). Statistical significance was tested using

least significant difference (LSD) at the p!0.05 level and

the results shown are the meanGstandard deviation.

3. Results

3.1. Effects of organic loading on the SBR system

The SBR system was operated with milk industrial

wastewater (Table 2) under HRTs of 3, 4, 6 and 8 d as

shown in Table 3. The results are shown in Fig. 3, Tables 4

and 5. The system under the organic loading of up to

1000 g BOD5/m3 d reached steady state within 9–10 d of

acclimatization while it was delayed to about 12 d under the

organic loading of 1340 g BOD5/m3 d as shown in Fig. 3.

Also, the effluent qualities of the system were almost stable

when the organic loading was decreased. The standard

deviation of effluent BOD5 under the organic loading of

1340 g BOD5/m3 d was 12 while it was only 5 under the

organic loading of 500 g BOD5/m3 d as shown in Table 4.

The removal efficiencies of the system increased with

decreased organic loading or increased HRT, as shown in

Table 4. The BOD5 removal efficiency of the system under

the lowest organic loading of 500 g BOD5/m3 d was 10%

higher than that under the highest organic loading of

1340 g BOD5/m3 d as shown in Table 4. The amount of

excess bio-sludge was also increased with the increase in

organic loading as shown in Table 5. An amount of 13.5G

1.72 g/d of bio-sludge was wasted in the system with

organic loading of 1340 g BOD5/m3 d while it was only

3.4G0.47 g/d at an organic loading of 500 g BOD5/m3 d.

The SRT of the system under the lowest organic loading of

500 g BOD5/m3 d was 15 d longer than under the highest

organic loading of 1340 g BOD5/m3 d. Also, the SVI

increased with increased organic loading, as shown in

Table 5. The SVI of the system under the highest organic

loading of 1340 g BOD5/m3 d was 3 times higher than under

the lowest organic loading of 500 g BOD5/m3 d.

3.2. Effects of organic loading on MSBR system

The MSBR system was operated with milk industrial

wastewater under various HRT similar to the experiment

with the SBR system above (Table 3). The results are shown

in Fig. 4, Tables 6 and 7. The system under the organic

loading of up to 1000 g BOD5/m3 d reached steady state

Fig. 3. Effluent BOD5, COD, TKN, and oil & grease profiles of SBR system %, 1340 g BOD/m3 d; &, 1000 g BOD/m3 d; :, 680 g BOD/m3 d; !,

500 g BOD/m3 d.

180 S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177–183 within 5–6 d of acclimatization and maintained an almost

stable removal efficiency as shown in Table 6. The standard

deviation of the BOD5 removal efficiency was only 0.1. But

it was delayed to about 7–8 d under the highest organic

loading of 1340 g BOD5/m3 d as shown in Fig. 4. The

excess bio-sludge of the system under the organic loading of

1340 g BOD5/m3 d was about 6.7G0.93 g/d while there

was almost no excess sludge under the organic loading of up

to 680 g BOD5/m3 d. The bio-film mass on the media also

increased with increased organic loading, as shown in

Table 7. The total bio-film mass under the highest organic

loading of 1340 g BOD5/m3 d was 52.3G0.47 g while it

was only 35.5G0.21 g under the lowest organic loading

of 500 g BOD5/m3 d. The total bio-sludge mass values

Table 5

Properties of bio-sludge of SBR system under various HRTs of 3, 4, 6, 8 days

HRT (d) Organic loading

(g BOD/m3 d)

Suspended bio-sludge:

MLSS (mg/l)

F/M (dK1) Excess sludge

(g/d)

Sludge age

(SRT) (d)

SVI (ml/g)

3 1340 3500G320 0.38G0.03 13.5G1.72 5.2G0.41 142G13.1

4 1000 3500G193 0.29G0.02 10.3G1.14 6.8G0.57 97G8.9

6 680 3500G107 0.19G0.02 5.6G0.96 12.5G0.92 70G6.6

8 500 3500G96 0.14G0.01 3.4G0.47 20.6G1.77 55G4.8

Table 4

Effluent qualities and removal efficiencies of SBR system under various HRTs of 3, 4, 6, 8 days HRT (d) Organic loading

(g BOD/m3 d)

COD BOD TKN Oil & grease Effluent

SS (mg/l)

Effluent

(mg/l)

% Removal Effluent

(mg/l)

% Removal Effluent

(mg/l)

% Removal Effluent

(mg/l)

% Removal

3 1340 912G16 87.0G0.2 805G12 79.9G0.3 51G2 48.7G1.7 41G3 79.3G1 100G12

4 1000 456G11 93.5G0.2 423G10 89.4G0.3 44G1 56.4G0.8 26G1 87.1G0.6 80G10

6 680 190G8 97.3G0.1 176G8 95.6G0.2 38G1 62.3G1.0 16G1 92.1G0.6 25G6

8 500 122G4 98.3G0.1 106G6 97.4G0.2 21G1 79.4G1.1 11G1 94.6G0.5 15G5

Fig. 4. Effluent BOD5, COD, TKN, and oil & grease profiles of MSBR system %, 1340 g BOD/m3 d; &, 1000 g BOD/m3 d; :, 680 g BOD/m3 d; !,

500 g BOD/m3 d.

S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177–183 181 of the system under organic loadings of 1340 and

500 g BOD5/m3d were 112.3G13.1 and 91.5G8.6 g,

respectively. Then, the F/M ratios of the system under

the above organic loadings were 0.22G0.02 and 0.11G

0.01 dK1, respectively. The removal efficiencies of the

system increased with increased HRT or decreased organic

loading, as shown in Table 6. The BOD5 removal efficiency

of the system under organic loading of 1340 g BOD5/m3 d

was about 15% lower than under organic loading of

500 g BOD5/m3 d. The SVI of the bio-sludge was less

than 100 ml/g, even when the system was operated under

the highest organic loading of 1340 g BOD5/m3 d, as shown

in Table 7. However, the system under an organic loading of

up to 680 g BOD5/m3 d showed the optimal COD, BOD5,

TKN and oil & grease removal efficiencies of 97.9G0.0,

97.9G0.1, 79.3G1.0 and 94.8G0.5%, respectively, with

good settling of bio-sludge (SVI of 44G3.4 ml/g) and

without wasting any bio-sludge.

3.3. Comparison of the efficiencies of SBR

and MSBR systems

The results are shown in Tables 4–7 and Figs. 3 and 4.

The MSBR system was 2–3 d faster than the SBR system in

reaching steady state and maintained almost stable removal

efficiencies due to the low standard derivation values as

shown in Tables 4 and 6. The COD, BOD5, TKN and oil &

grease removal efficiencies of the SBR and MSBR systems

under the highest organic loading of 1340 g BOD5/m3 d

were 87.0G0.2, 79.9G0.3, 48.7G1.7 and 79.3G1%, and

89.3G0.1, 83.0G0.2, 59.4G0.8, and 82.4G0.4%, respectively,

as shown in Tables 4 and 6. The total bio-sludge of the

MSBR system was higher than the total bio-sludge of

the SBR system in all cases of operation. The F/M of the

MSBR system was lower than that of the SBR system

under the same organic loading, as shown in Tables 5 and 7.

The F/M of the MSBR and SBR systems under organic

loading of 680 g BOD5/m3 d were 0.13G0.01 and 0.19G

0.02 dK1, respectively. Also, the amount of excess biosludge

of the MSBR system was lower than that of the SBR

system under the same organic loading as shown in Tables 5

and 7. The excess bio-sludge of the MSBR and SBR systems

under the highest organic loading of 1340 g BOD5/m3 d

were 6.7G0.93 and 13.5G1.72 g/d, respectively, and the

amount of excess bio-sludge waste of the MSBR system

under an organic loading of up to 680 became zero. The

quality of bio-sludge of the MSBR system was better than

that of the SBR system due to the SVI value. The SVI of the

MSBR system under organic loading of 1340 g BOD5/m3 d,

or HRT of 3 d was only 97G8.3 ml/g while it was 142G

13.1 ml/g in the SBR system as shown in Tables 5 and 7.

4. Discussion and conclusions

It can be suggested that the application of an attached

growth system, by installing plastic media (2.7 m2 surface

area) on the bottom of the SBR system to obtain a MSBR

system, could increase the removal efficiencies, improve

sludge quality, reduce the amount of excess bio-sludge, and

also reduce the acclimatization period of the system. The

acclimatization time of the MSBR system was 2–3 d shorter

than that of the SBR system. The COD and BOD5 removal

efficiencies of the MSBR system were about 5–7% higher

than those of the SBR system under the same organic

loading condition. This can be explained by the fact that the

total bio-sludge mass of the MSBR system was higher than

that of the SBR system due to the increased amount of

biofilm mass on the media of the MSBR system (Wanner

et al., 1998; Watanabe et al., 1994), and as a result

the MSBR showed a higher removal efficiency than the SBR

system (Gebara, 1999). Another advantage of the MSBR

Table 6

Effluent qualities and removal efficiencies of MSBR system under various HRTs of 3, 4, 6, 8 days HRT (d) Organic loading

(g BOD/m3 d)

COD BOD TKN Oil & grease Effluent

SS (mg/l)

Effluent

(mg/l)

% Removal Effluent

(mg/l)

% Removal Effluent

(mg/l)

% Removal Effluent

(mg/l)

% Removal

3 1340 750G7 89.3G0.1 681G10 83.0G0.2 41G1 59.4G0.8 35G1 82.4G0.4 75G11 4 1000 403G6 94.2G0.1 323G6 91.9G0.1 31G1 69.4G1.0 22G3 89.1G1.7 62G8 6 680 150G3 97.9G0.0 120G3 97.0G0.1 21G1 79.3G1.0 11G1 94.8G0.5 15G6 8 500 102G2 98.6G0.0 91G4 97.7G0.1 13G1 87.0G1.3 6G1 97.1G0.5 10G7

Table 7

Properties of bio-sludge of MSBR system under various HRTs of 3, 4, 6, 8 days HRT (d) Organic loading

(g BOD/m3 d)

SVI (ml/g) Suspended bio-sludge (MLSS) Sludge age

(SRT) (d)

Bio-film mass

(g)

Total biosludge

(g)

F/M (dK1)

MLSS in the

reactor (mg/l)

Excess biosludge

(g/d)

3 1340 97G8.3 3500G174 6.7G0.93 10.5G1.02 52.3G0.47 122.3G13.1 0.22G0.02 4 1000 50G5.2 3500G113 3.9G0.61 18.2G1.68 45.2G0.34 115.2G15.2 0.17G0.02 6 680 44G3.4 3250G84 – – 38.4G0.36 103.4G9.4 0.13G0.01

8 500 44G2.8 2800G56 – – 35.5G0.21 91.5G8.6 0.11G0.01

182 S. Sirianuntapiboon et al. / Journal of Environmental Management 76 (2005) 177–183 system was the low excess sludge generation due to the high

total bio-sludge mass in the reactor (Metcalf & Eddy, 1991;

Gebara, 1999). The increasing total bio-sludge mass of the

system resulted in the reduction of the F/M of the system

(Metcalf & Eddy, 1991; Gebara, 1999) and the reduction of

the amount of excess bio-sludge production (Metcalf &

Eddy, 1991; Gebara, 1999; Chudoba et al., 1998). The

amount of excess bio-sludge produced by the SBR system

under an organic loading of 1340 g BOD5/m3 d was about 2

times higher than that of the MSBR system, as shown in Tables 4 and 6. The amount of excess bio-sludge of the MSBR system became zero when the organic loading was down to 680 g BOD5/m3 d due to the low growth rate of bio-sludge under low F/M conditions and endogenous respiration (Metcalf & Eddy, 1991). The TKN removal efficiency of both the SBR and MSBR systems was

increased with an increase in HRT or decrease in organic loading because the increase in HRT or decrease in organic loading resulted in increasing the population of nitrification bacteria due to the increase in the sludge age or SRT (Metcalf & Eddy, 1991; Gebara, 1999; Irvine and Busch, 1979; Shin et al., 1998; Helmer and Kunst, 1998). The TKN was removed by both assimilation and nitrification mechanisms in the MSBR reactor (Sirianuntapiboon and Tondee,

2000; Shin et al., 1998; Keller et al., 1997; Kagi and Uygur, 2002). However, the MSBR system showed a higher TKN removal efficiency than the SBR system because the total bio-sludge mass of the MSBR was higher than that of the SBR system. Also, the bio-sludge of the MSBR system was more settled, because the SRT of the MSBR system was higher than the SRT of the SBR system (Metcalf & Eddy, 1991; Gebara, 1999; Irvine and Busch, 1979; Keller et al., 1997).

In application, the MSBR system could be suitable for use in the treatment of milk industry wastewater due to the high organic carbon and nitrogen removal efficiencies, good quality of bio-sludge, and low amount of excess bio-sludge waste. The optimal removal efficiency of the MSBR system with milk industrial wastewater was observed under an organic loading of up to 680 g BOD5/m3 d.

Acknowledgements

The author wishes to express deep thanks to the

Department of Environmental Technology, King Mongkut’s University of Technology Thonburi and the Chin

Sophonpanith Foundation for providing the research materials, equipment and funds.

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