ORIGINAL PAPER

Performance evaluation of full-scale upflow anaerobic sludgeblanket reactor treating distillery spentwash

M. Selvamurugan • P. Doraisamy • M. Maheswari •

K. Valliappan

Received: 1 December 2010 / Accepted: 9 June 2011 / Published online: 22 June 2011

� Springer-Verlag 2011

Abstract Performance of full-scale upflow anaerobic

sludge blanket (UASB) reactors treating distillery spent-

wash was evaluated. The plant was designed to handle

650 m3 day-1 of distillery spentwash having an average

chemical oxygen demand (COD) concentration of

112,400 mg l-1 with a HRT of 6 days. In the plant, the pH

level of the influent varied from 3.50 to 4.40 but the pH of

the treated effluent stabilized to a range of 7.36 to 7.68

during the study period. The operation of the reactors

during study period revealed the stable conditions of the

reactors, which is evident from the low COD, biochemical

oxygen demand (BOD) and total solids (TS) contents in

treated effluent. In the plant, the COD, BOD5 and TS

removal efficiencies were stabilized to the range of

62.19–66.59, 72.42–77.11, and 58.47–60.46%, respectively

at an organic loading rate of 2.15–4.60 kg COD m-3

day-1. The biogas production was stabilized to the range of

48,290–135,115 m3 week-1 with 60% methane content.

The total quantity of biogas produced ranged from 0.40 to

0.57, 1.04 to 1.71 and 0.40 to 0.56 m3 kg-1 removals of

COD, BOD and TS, respectively. This study concluded

that the treatment of distillery spentwash using UASB

reactors contributed significantly for pollution load reduc-

tion besides generating renewable in-house bio-energy.

Keywords Distillery spentwash � UASB reactor �Performance

Introduction

Production of ethanol from agricultural materials via fer-

mentation process is very attractive, due to the fast depletion

of fossil fuel and fluctuation of oil and natural gas prices.

Among the raw materials used for ethanol production,

molasses is the most widely used material because of its low

cost, availability and suitability for fermentation process.

Being rich sugarcane yield in India, all the ethanol is pro-

duced by the process of fermentation of molasses and its

subsequent distillation (Saha et al. 2005). At present, there

are 319 distilleries in India with an installed capacity of 3.25

billion liters of alcohol, which are generating 40.4 billion

liters of distillery spentwash annually (Mohana et al. 2009).

The effluent from molasses-based distilleries contains all the

ingredients found in the molasses except fermentable sugar

which will create many environmental pollution problems

(Pazouki et al. 2008). It is considered as a very high strength

wastewater having very high COD and BOD5 with low pH

and dark brown color (Goel and Chandra 2003). This dark

brown colored effluent, when discharged into water bodies

without proper treatment, defiles the natural ecosystem

(FitzGibbon et al. 1998). Problems like adequate treatment

and disposal of distillery spentwash and the development of

new water sources for irrigation can be related and solved

using the proper technologies. Anaerobic treatment is an

accepted technology for the treatment of distillery spentwash

and various high rate reactor designs have been tried at pilot

and full-scale operation. It is an attractive primary treatment

for distillery spentwash due to its reputation as low energy

consumption, less sludge production, high organic loading

rate (OLR) can be applied, environment friendly and socio

economically acceptable technology (Acharya et al. 2008).

The upflow anaerobic sludge blanket (UASB) reactor

technology is considered as the breakthrough in the

M. Selvamurugan (&) � P. Doraisamy � M. Maheswari �K. Valliappan

Department of Environmental Sciences, Tamil Nadu

Agricultural University, Coimbatore, Tamil Nadu, India

e-mail: muruganens@gmail.com

123

Clean Techn Environ Policy (2012) 14:267–271

DOI 10.1007/s10098-011-0396-7

development and application of anaerobic technology for

industrial wastewater. After the initial first trials in the

1970s, the system rapidly became popular, particularly in

the agro-industry sector. The UASB process occupies more

than 50% of anaerobic treatment plants installed around the

world (Van Lier 2008). This reactor, as originally proposed

by Lettinga, was one of the earliest systems in which

development of a granular biomass was observed. As the

result of the excellent settling characteristics of this gran-

ular biomass and the presence of a specially designed

three-phase (biogas, water and biomass) separator device in

the upper part of the UASB reactor, an excellent sludge

retention is assured in this reactor system (Frankin 2001).

The major disadvantage of the UASB process comprises,

although merely in those cases where proper seed sludge is

not available in sufficient quantities, the relatively long

start-up period. Many factors viz., temperature, wastewater

composition, pH, organic loading rate and toxicity have

been found to affect the efficiency of UASB reactors

(Lettinga and Hulshoff Pol 1991). Therefore, it is necessary

to monitor all process parameters viz., pH of the waste-

water in reactor, reduction of pollution load and biogas

production at regular intervals for treating distillery

spentwash effectively. In this article, the performance of

full-scale UASB reactors were evaluated for treating dis-

tillery spentwash at wastewater treatment plant of Bhavani

Distilleries and Chemicals Ltd., T. Pudhur, Vellore district,

Tamil Nadu, India and the performance of the reactors

under various operating conditions are elucidated.

Materials and methods

Description of the UASB reactors

Flow diagram of the wastewater treatment processes is

given in Fig. 1. The plant is designed to handle

650 m3 day-1 of distillery spentwash having an average

COD concentration of 112,400 mg l-1 with a hydraulic

retention time of 6 days. The raw distillery spentwash is

received in a buffer tank where the pH of spentwash is

raised from 4.0 to 6.5–7.0 through re-circulation of efflu-

ents from two reactors to buffer tank and addition of

Ca(OH)2 and nutrients, such as, urea and di-ammonium

phosphate. From the buffer tank, the wastewater is fed into

two anaerobic reactors through reactor feed pumps. The

treated effluent from the reactors is sent to aerobic storage

lagoon and it is disposed off either into compost yard for

composting the pressmud or directly for crop productivity.

Biogas generated in the reactor is passed through foam

trap, sediment trap, and moisture trap and stored in gas

holder. From the gas holder, the biogas is used in the

blower to produce steam. The gas-handling system is also

provided with flaring system to flare the biogas when it is

not used in the blower. The reactors are operated at an

ambient temperature without any heating and cooling

system.

Pre-commissioning and start up of reactors

Both the reactor I (capacity 6,585 m3) and II (capacity

5,682 m3) were inoculated with sludge having volatile

suspended solids of 50 kg m-3. Thirty tonnes of seed

sludge was used for each reactor. The reactor was started

with 500 m3 day-1 distillery spentwash (Table 1) feeding

by batch process during day time and scaled up to

120 m3 day-1 through continuous feeding within 15 days

and then the feed rate was increased by 10–20% every

week.

Sample collection and analytical methods

The samples of raw spentwash and the effluent in the buffer

tank, reactor I and reactor II outlets were collected once in

a week from January 2010 to March 2010 and analyzed for

pH, EC, TS, COD and BOD as per the Standard Methods

for the Examination of Water and Wastewater (APHA

1992).

The biogas generation and wastewater inlet flow were

measured using magnetic flow meters installed in the

respective place at normal pressure and temperature.

The methane content in biogas was measured by Gas

Fig. 1 Process flow diagram

of UASB biomethanation plant

268 M. Selvamurugan et al.

123

chromatography, with thermal conductivity detector having

‘Porapak Q’ column by setting the oven temperature at

80–100�C, injector temperature at 100–200�C, detector

temperature at 120�C and using nitrogen as carrier gas at a

flow rate of 30 ml min-1. The furnace oil saving was

calculated directly based on the reduction in the specific

consumption per day before and after biogas firing.

Results and discussions

The pH of the raw effluent ranged from 3.50 to 4.40. The

acidic pH of the feed is neutralized by adding Ca(OH)2 in

buffer tank that increases the pH and alkalinity, which are

essential for biomethanation (Lowe et al. 1993). The re-

circulation of the effluent from both reactors to buffer tank

also increases the pH. The pH of treated effluent (Fig. 2)

stabilized to the range of 7.36–7.68 during study period.

Good buffering capacity in the reactor and higher microbial

activity might be the reason for the increase in pH. In

general, the rise in pH is due to ammonia production during

the process of digestion. During the treatment of dairy

wastewater using UASB system, an increase in pH up to

6.61 was reported by Mahadevaswamy et al. (2004). Banu

et al. (2006) achieved a neutral pH during the treatment of

sago wastewater using Hybrid UASB reactor.

As expected, COD reduction was observed in each

stage, starting from the buffer tank. The reduction in COD

content and further increase in pH and alkalinity across

reactor are good indications for the conversion of most of

the organic compounds into methane and CO2. The oper-

ation of the reactors during study period revealed the stable

operations, which is evident from the low COD values of

treated effluent. Weekly average COD reduction in spent-

wash is presented in Fig. 3. In this study, better perfor-

mance of reactors was achieved with 62.19–66.59% of

COD removal, which might be due to better granulation in

the reactor. High COD reduction can be attributed to the

development of an active microflora in the UASB reactor

and the biodegradability of the substrate. Fang and Chui

(1993) reported that the COD removal efficiency of the

UASB reactor was mainly dependent on the COD loading

rate and HRT of the reactor operation. In this study, the

average values of OLR during study period ranged from

2.15 to 4.60 kg COD m-3 day-1. Similar trend of results

were obtained by Goodwin et al. (2001) who found that

when malt whisky distillery wastewater was fed into an

UASB reactor, COD reductions of more than 80% occurred

at an OLR of 5.46 kg COD m-3 day-1. Kalyuzhnyi et al.

(2001) also achieved a COD reduction of 60% in one-stage

UASB reactor in treating distillery waste with an organic

loading rate varied from 4.7 to 1.3 g COD at a HRT of

6–7 days. Wolmarans and de Villiers (2002) also achieved

a COD reduction of 90% during anaerobic treatment of

distillery effluent.

Weekly average values of BOD5 in the raw spentwash,

buffer tank, UASB I, and II outlets are presented in Fig. 4.

During the study period, the BOD5 reduction of the reactor

ranged from 21,305 to 28,105 mg l-1. The BOD5 removal

efficiency was stabilized to a range of 72.42–77.11%. As

the stabilization of microbial consortium takes place the

bioconversion rate is also improved with enhanced sub-

strate utilization. Hence the BOD5 removal efficiency was

stabilized to a level of 72.42–77.11%. Wolmarans and de

Villiers (2002) achieved a BOD5 reduction of 80–90% for

the anaerobic treatment of distillery effluent.

Table 1 Characteristics of distillery spentwash

Parameters Concentration

pH 3.50–4.40

EC (dS m-1) 40.50–44.60

Total solids (mg l-1) 118,955–121,480

Biochemical oxygen demand (mg l-1) 39,420–46,870

Chemical oxygen demand (mg l-1) 108,950–116,800

3

4

5

6

7

8

9

pH

1 2 3 4 5 6 7 8 9 10 11 12 13

pH

Period (weeks)Raw effluent Buffer tank UASB-I outlet UASB-II outlet

Fig. 2 Weekly average values of pH during study period

Period (weeks)

55

60

65

70

1 2 3 4 5 6 7 8 9 10 11 12 13

CO

D r

edu

ctio

n (

%)

Fig. 3 COD reduction in reactor during study period

Performance evaluation of full-scale UASB reactor 269

123

The average TS removal efficiency of the reactor during

the study period of operation was stabilized to a range of

58.47–60.46%. Hickey et al. (1991) have reported that the

change in pH from slight acidic to near neutral facilitates

the proper growth of the bacterial population which in turn

results in the increased TS reduction. Similar trend of

results were obtained by Banu et al. (2006) who achieved

the TS removal efficiency of 57–61% during the treatment

of sago wastewater using hybrid UASB reactor.

The biogas production was stabilized to a range of

48,290–135,115 m3 week-1 during the study period. The

high and stabilized biogas production was attributed to the

development of an active microflora in UAHR and com-

plete conversion of organic matter into biogas as observed

by the reduction in BOD5, COD and TS. Lettinga (1995)

also reported that the reduction of BOD5 and COD con-

tributes to the gas production. The gas production was less

during 9th and 10th weeks when compared to other periods

due to low receipt of spentwash during the off-season

resulting in less COD in the spentwash. Weeklywise total

spentwash feed, COD feed, COD out, COD reduced in

reactor, and biogas produced are presented in the Table 2.

The maximum gas production was achieved at 12th week

which coincides with high wastewater feed and COD

content in the feed (Fig. 5) as reported in pilot plant study

with pulp and paper industry wastewater (Chinnaraj et al.

2001). The total quantity of biogas produced ranged from

0.40 to 0.57; 1.04 to 1.71; and 0.40 to 0.56 m3 kg-1 of

COD, BOD5 and TS removed, respectively. Similarly

biogas production of 0.52 m3 kg-1 of COD removal was

achieved in the treatment of bagasse-based pulp and paper

industry wastewater using UASB reactor under pilot plant

study (Chinnaraj and Venkoba Rao 2006). Shaji James and

Kamaraj (2003) also achieved the biogas production of

0.55 m3 kg-1 of TS removed in the treatment of cassava

starch factory effluent using UAHR. Diamantis et al.

(2005) also achieved a biogas production of 0.24 m3 kg-1

of COD removed in biomethanation of fruit canning

wastewater through hybrid reactor.

During study period, the methane rich biogas produced

in the biomethanation process was utilized in the power

boiler as in-house fuel to reduce furnace oil utilization. The

overall furnace oil saving from January 2010 to March

2010 was found to be 1.57 lakh liters which is good rev-

enue. During the month of March 2010, cost of 1 l furnace

oil was around Rs. 28.50 (1US $ = Rs. 44) and average

saving for 3 months works out to be around Rs.

44.74 lakhs.

Biogas use in power boiler resulted in significant

amount of furnace oil saving leading to cut down of CO2

Raw effluent Buffer tank UASB-I outlet

5000

10000

15000

20000

25000

30000

35000

40000

45000

50000

1 2 3 4 5 6 7 8 9 10 11 12 13

BO

D (

mg

L-1

)

Period (weeks)

UASB-II outlet

Fig. 4 Weekly average values of BOD during study period

Table 2 Weekly spentwash feed, COD feed, COD out and biogas production performances during study period

Period

(weeks)

Spentwash

feed

(m3 week-1)

COD feed to

reactor

(kg week-1)

COD out

from reactor

(kg week-1)

Total biogas

production

(m3 week-1)

Biogas

production

(m3 kg-1 of COD

reduction)

Biogas

production

(m3 kg-1 of BOD

reduction)

Biogas

production

(m3 kg-1 of TS

reduction)

Methane

content

(%)

1 2396.96 269,850 100,984 92,650 0.55 1.12 0.55 60

2 2576.82 284,945 107,750 100,528 0.57 1.02 0.55 61

3 2960.24 334,181 121,977 114,526 0.54 1.13 0.55 59

4 2500.59 283,067 104,000 95,596 0.53 1.12 0.54 59

5 2769.41 308,512 113,864 106,238 0.55 1.18 0.55 62

6 3482.02 384,415 141,718 131,186 0.54 1.07 0.52 61

7 3453.3 394,988 138,512 131,798 0.51 1.03 0.53 61

8 3241.76 371,376 129,670 125,773 0.52 1.18 0.55 59

9 1901.23 208,546 70,431 70,877 0.51 1.03 0.52 58

10 1657.33 184,958 63,418 48,290 0.4 0.77 0.4 60

11 2969.86 323,566 113,256 115,340 0.55 1.24 0.54 60

12 3357.83 392,195 131,023 135,115 0.52 1.18 0.56 61

13 3090.95 352,832 119,450 133,727 0.49 0.99 0.53 60

270 M. Selvamurugan et al.

123

emission to atmosphere from fossil fuel. Therefore,

anaerobic treatment of spentwash using UASB reactors

contributes significantly reduction of pollution load and, to

reduce green-house gas emissions, and generate renewable

in-house bio-energy which can be used in the plant and

generate revenue to industry.

Acknowledgments The authors wish to express their gratitude to

the Bhavani Distilleries and Chemicals Ltd., T.Pudhur, Vellore dis-

trict, Tamil Nadu, India for providing financial support through a

Project on ‘‘High rate biomethanation and eco-friendly utilization of

spentwash for sustainable agriculture.’’

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0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

1 2 3 4 5 6 7 8 9 10 11 12 13

m3

day

-1

Period (weeks)

Spentwash feed Total biogas production

Fig. 5 Weekly average values of spentwash feed and total biogas

production during study period

Performance evaluation of full-scale UASB reactor 271

123