RESEARCH ARTICLE

Treatment of Sugar Industry Wastewater in Anaerobic DownflowStationary Fixed Film (DSFF) Reactor

N. V. Pradeep • S. Anupama • J. M. Arun Kumar •

K. G. Vidyashree • P. Lakshmi • K. Ankitha •

J. Pooja

Received: 19 February 2013 / Accepted: 7 June 2013

� Society for Sugar Research & Promotion 2013

Abstract The consumption of large volumes of water and

the generation of organic compounds as liquid effluents are

major environmental problems in sugar cane processing

industry. The aim of this work is to study the treatment of

synthetic sugar wastewater by a downflow stationary fixed

film (DSFF) reactor. The reactor was fabricated and packed

with polyvinyl chloride pipe pieces and it was air tight

sealed to maintain anaerobic conditions. The ambient room

temperature during the study period was between 29 and

33 �C. Start-up period required by the reactor was 3 weeks.

Initially a hydraulic retention time (HRT) of 48 h was set,

HRT was decreased when the reactor reached steady state.

BOD and COD removal increased as the HRT decreased

from 48 to 12 h. BOD and COD removal was 79 and 81.8 %

respectively at 12 h HRT. A decline in removal was noticed

when the HRT was set to 6 h. Biogas production was

445 ml/day at 12 h HRT. Differential staining was carried

out, it revealed that the micro-organisms belong to gram

negative class. Thus DSFF reactor can be used for treating

sugar wastewater and for producing biogas.

Keywords Anaerobic treatment �Downflow stationary fixed film reactor �Sugar wastewater � COD � HRT

Introduction

Benjamin Franklin said that ‘‘we know the worth of water

when the well is dry’’ (Zaidi 2007). Water is extensively

used by process industries, but its consumption is not

always formulated in a rational way. Due to the growing

demand of water by population and industries, it is nec-

essary to take into account the emerging problem of water

supply (Ingaramo et al. 2009). The industrialization and

modification of manufacturing processes have resulted in

an increase in the volume of wastewater discharge into the

environment which causes water pollution (Asaithambi and

Matheswaran 2011). It is estimated that over 80 % of the

wastewater generated across the world are not presently

collected or treated (Tauseef et al. 2013). Water pollution

by organic and inorganic compounds is of great public

concern (Gupta et al. 2002). Wastewater organic matter is

highly heterogeneous, containing molecules of various

molecular weights, ranging from the simple compounds

like acetic acid, to very complex polymers (Dignac et al.

2000).

There are more than 550 sugar industries in India

(Hampannavar and Shivayogimath 2010). Effluents from

sugar industries induce environmental pollution. India,

being one of the major producers of sugar in the world

is prone to large volume of wastes the sugar industry

(Parande et al. 2009). The sugar industry generate about

1,000 l of wastewater for every ton of sugar cane crushed

(Hampannavar and Shivayogimath 2010). The wastewater

effluents from the sugar industry are highly variable in both

quantity and quality depending on the product produced

(Hamoda and AI-Sharekh 1999). Sugar refineries generate

a highly coloured effluent resulting from the regeneration

of anion-exchange resins (used to decolourize sugar

liquor). This effluent represents an environmental problem

due to its high organic load, intense colouration and pres-

ence of phenolic compounds (Guimaraes et al. 2005). The

byproducts namely bagasse, molasses, distillery wastes and

pressmud are some of the major objectionable wastes

N. V. Pradeep (&) � S. Anupama � J. M. Arun Kumar �K. G. Vidyashree � P. Lakshmi � K. Ankitha � J. Pooja

Department of Biotechnology, Ballari Institute of Technology

and Management, Bellary, India

e-mail: nagamallivpradeep@gmail.com

123

Sugar Tech

DOI 10.1007/s12355-013-0227-8

generated by the sugar industries (Parande et al. 2009).

Because of high BOD content, sugar industry wastewater

will deplete dissolved oxygen content of water bodies

rendering them unfit for both aquatic life and human uses

(Hampannavar and Shivayogimath 2010).

Various physico-chemical and biological treatment

options are available for the treatment of wastewaters

(Anupama et al. 2013). Biological treatment methods are

gaining more importance over physico-chemical methods.

Biological methods produce simple and harmless end

products due to microbial action. Decomposition of bio-

degradable organic waste can occur both aerobically and

anaerobically (Tauseef et al. 2013).

Anaerobic digestion is a biological process in which a

group of microorganisms biodegrade the organic matter

(substrate) in the absence of free molecular oxygen (O2).

As a result of this complex biological process, organic

matter is mainly converted into a mixture of methane

(CH4) and carbon dioxide (CO2) as well as new bacterial

cells (Alkaya and Demirer 2011b). In anaerobic processes,

the methanogenic bacteria are pH sensitive and have a

narrower optimum range of pH: 6.5–7.5 (Clark and Speece

1971). Anaerobic treatment of concentrated wastewater is

widely accepted practice in industries (Farhadian et al.

2007). It is one of the several biological processing strat-

egies which produce bioenergy and/or biochemicals while

treating industrial and agricultural wastes (Alkaya and

Demirer 2011a). The process of anaerobic digestion has

been greatly developed during the last two decades for the

treatment of wastewater from food industries (Hu et al.

2002). In recent years, considerable attention has been paid

towards the development of reactors for anaerobic treat-

ment of wastes leading to the conversion of organic mol-

ecules into biogas (Rajeshwari et al. 2000). Biogas

produced could be economically reused to substitute most

or all fossil fuels used for process thermal energy genera-

tion (Malaspina et al. 1995).

The successful application of anaerobic technology to

the treatment of industrial wastewaters is critically depen-

dent on the development and use of high rate anaerobic

bioreactors (Barber and Stuckey 1999). The anaerobic filter

is a treatment system that meets these specifications for the

treatment of sewage and industrial waste. Its operating

principle is based on immobilizing microorganisms on a

support (Colin et al. 2007) which increases the microbial

residential time, thus reducing wash-out (Lomas et al.

2000). The downflow stationary fixed film (DSFF) reactor

contains solid packing similar to anaerobic filters but is

operated in the downflow mode, the wastewater enters from

the top and flows downwards (Tauseef et al. 2013). The

downflow mode of operation was found to be more trouble-

free than the upflow mode as described by Samson and

Kennedy (1985).

High-rate anaerobic reactors are becoming increasingly

popular for the treatment of various types of wastewater

because of their low initial and operational costs, smaller

space requirements, high organic removal efficiency and

low sludge production, combined with a net energy benefit

through the production of biogas (Jawed and Tare 2000).

The anaerobic treatment of food industry effluents con-

taining high concentrations of soluble organic matter is

attractive because of the high methane yields and the

potential for net energy production (Borja and Banks

1995). The sugar industry was one of the first industries in

Germany to carry out anaerobic wastewater treatment. The

first methane reactor for a sugar factory started to work in

1979. Today, over 50 % of the sugar factories in Germany

clean their wastewater aerobic and/or anaerobically (Haun

et al. 1997).

In the present investigation an anaerobic downflow

stationary fixed film (DSFF) reactor was fabricated and was

used for the treatment of synthetic sugar industry waste-

water and to generate biogas as by-product.

Materials and Methods

Reactor Fabrication

A laboratory scale anaerobic downflow stationary fixed

film (DSFF) reactor was fabricated. Polyvinyl chloride

(PVC) pipe was used for the fabrication of the reactor.

Overall height, diameter and other design specifications are

given in Table 1. Inlet and outlet for the wastewater were

provided at a distance of 15 cm from top and bottom of the

reactor column respectively. Biogas evolved was collected

by water displacement method. Ball valve was fixed at the

bottom of the reactor to withdraw sludge. The reactor was

supported by iron frame; the schematic representation of

this experimental setup is shown in Figs. 1 and 2. PVC

pipe pieces were used as packing material in the reactor

and are as shown in Fig. 3 (Rajeshwari et al. 2000). Pipe

fittings were completely sealed to avoid air entry and to

ensure anaerobic conditions in the reactor.

Start-Up Period

Cow dung was mixed with water and was sieved to remove

large debris; the filtrate was used as seed for the reactor.

Minimal nutrients and carbon source was provided for

micro-organisms. Reactor during the start-up period was in

batch mode. Two weeks after the inoculation, carbon

dioxide gas was released and after third week methane gas

(biogas) was released. Biogas produced was burnt; the

flame was blue indicating the gas to be methane. Gradually

the wastewater was allowed in the reactor in a continuous

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mode from an initial hydraulic retention time (HRT) of

42 h.

Composition and Analysis of Wastewater

Sugar industry wastewater was prepared synthetically

using the components as prescribed by Guiot and Berg

(1984) and was used for the study. Composition of syn-

thetic sugar wastewater is given in Table 2. The samples

were collected from the feed tank and from the outlet

provided in the reactor. These were analysed periodically

as per the methods described in Standard methods by

American Public Health Association, American Water

Works Association (Standard Methods for Examination of

Water and Wastewater 1985).

Fig. 1 Ray diagram of reactor

Fig. 2 Reactor set-up

Fig. 3 Packing material

Table 1 Reactor design specification

Specifications Value

Height (cm) 68.5

Diameter (cm) 10

Working volume (l) 6

Packing material filled (cm) 53

Diameter of packing material (cm) 0.63

Diameter of inlet and outlet ports (cm) 1.27

Diameter of sludge collection valve (cm) 2.54

Table 2 Composition of syn-

thetic sugar wastewater (Guiot

and Berg 1984)

Component Concentration

(g/l)

Sucrose 2.50

(NH4)2SO4 0.125

K2HPO4 0.065

KH2PO4 0.050

(NH4)HCO3 0.50

NaHCO3 4.00

KHCO3 4.00

Yeast extract 0.025

COD 2.5–3

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Experimental Conditions

The ambient room temperature during the study period was

between 29 and 37 �C. The flow rate, pH of the influent

and effluent; and quantity of the biogas generated were

recorded daily. Initially flow rate was set to obtain a HRT

of 42 h and was allowed to stabilize. HRT was varied when

there was no considerable difference in two consecutive

COD readings (i.e. after attaining steady state).

Examination of Microorganism in DSFF Reactor

Microbial analysis was carried out, the microorganisms

were isolated and were subjected to Differential Staining.

The Gram stain, developed in 1884 by the Danish physi-

cian Christian Gram, is the most widely employed staining

method in bacteriology. It is a differential staining proce-

dure because it divides bacteria into two classes—gram

negative and gram positive (Hogg 2005; Prescott et al.

2002). Gram staining was carried out as prescribed in

Harley and Prescott (2002).

Results and Discussion

Treatment of Wastewater at Varied HRT’s

HRT (hydraulic retention time) is a measure of average

length of time that a soluble compound remains in a con-

structed bioreactor. It is a measure of volume of the reactor

by flowrate of the wastewater. The BOD and COD of the

effluent were analyzed to know the removal efficiencies

during the study period. The initial COD of synthetic sugar

wastewater was 2,200 mg/l. HRT was initially set for 48 h

and was allowed to reach steady state. HRT was changed

when then was no was no considerable difference in two

consecutive COD readings. BOD and COD removal are

shown in Figs. 4 and 5 respectively.

BOD removal at 48, 24, 12 and 6 h of HRT was found to

be 38.90, 47.95, 79 and 60.22 % respectively. COD

removal at 48, 24, 12 and 6 h of HRT was found to be 41,

50, 81.8 and 61.8 % respectively.

BOD and COD removal efficiency gradually increased

from 48 to 12 h and a decline was observed at 6 h HRT.

Thus the optimum HRT required for maximum BOD and

COD was 12 h. COD removal efficiency at varied HRT’s is

shown in Fig. 6. Anupama et al. (2013) conducted similar

studies for BOD removal efficiency which reduced from

61.2 to 38.6 % for the varying feed concentrations of dis-

tillery spentwash.

Biogas Generation

One important factor for the selection of anaerobic treatment is

the possibility of energy recovery through biogas combustion

(Monroy et al. 2000). Biogas was generated as a by-product

during the anaerobic treatment of synthetic sugar industry

wastewater. The biogas generated was burnt, this produced blue

flame indicating the presence of methane. Biogas produced was

measured by water displacement technique.

Gopala Krishna et al. (2008) used water displacement

method for the collection and estimation of biogas produced

during the treatment of low strength wastewater in anaerobic

baffled reactor (ABF) (Gopala Krishna et al. 2008).

Figure 7 represents the biogas generated during the

operating period. The amount of biogas generated in ml/day

for 48, 24, 12, and 6 h of HRT is shown in Fig. 8. The biogas

0

200

400

600

800

0 2 4 6 8 10

BO

D in

mg/

L

Time in days

48Hrs

24Hrs

12Hrs

6 Hrs

Fig. 4 Removal of BOD at varied HRT’s

0

500

1000

1500

2000

2500

0 2 4 6 8 10

CO

D in

mg/

L

Time in Days

48Hrs

24Hrs

12Hrs

6 Hrs

Fig. 5 Removal of COD at varied HRT’s

0

20

40

60

80

100

612182430

HRT in h

364248

CO

D r

emov

al e

ffic

ienc

y in

%

Fig. 6 COD removal efficiency

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generated for 48, 24, 12, and 6 h of HRT was found to be 128,

300, 445 and 310 ml/day respectively, indicating maximum

amount of biogas generated at 12 h of HRT. At least 54 % of

the plants installed in Mexico do not even flare up the biogas

produced and rather vent it directly to the atmosphere, con-

tributing to the greenhouse effect (Monroy et al. 2000).

Microbial Examination

Microbial examination was carried out to know the class of

bacteria. Gram stating was carried out and the microor-

ganisms were observed under microscope. A thin microbial

layer was formed on the packing material as shown in

Fig. 9. It was observed that the microorganisms were gram

negative.

Conclusions

Conclusions drawn from the present study are as follows:

1. A lab scale anaerobic downflow stationary fixed film

(DSFF) reactor was fabricated and was used for

treating sugar wastewater.

2. Start-up period for the reactor to turn anaerobic was

3 weeks.

3. An increase in BOD and COD removal could be

observed as the HRT decreased from 48 to 12 h.

4. BOD and COD removal efficiencies were maximum at

12 h HRT when compared with various HRT’s during

the study period.

5. A BOD removal of 79 % and COD removal of 81.8 %

was observed at 12 h HRT.

6. Maximum biogas was generated as a by-product at

12 h HRT (445 ml/day).

7. A decrease in the COD and BOD removal efficiencies

were observed at 6 h HRT.

8. Microbial analysis revealed that the microorganisms

belonged to gram negative class.

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