Simultaneous biohydrogen production and wastewater treatment in biofilm configured anaerobic periodic discontinuous batch reactor using distillery wastewater

ARTICLE IN PRESS I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

33 (2008) 550– 558

Available at www.sciencedirect.com

journal homepage: www.elsevier.com/locate/ijhydene

Simultaneous biohydrogen production and wastewater treatment in biofilm configured anaerobic periodic discontinuous batch reactor using distillery wastewater S. Venkata Mohan, G. Mohanakrishna, S.V. Ramanaiah, P.N. Sarma Bioengineering and Environmental Centre, Indian Institute of Chemical Technology, Hyderabad 500007, India

ar t ic l e i n f o

abs tra ct

Article history:

Biohydrogen (H2) production with simultaneous wastewater treatment was studied in

Received 18 May 2007

anaerobic sequencing batch biofilm reactor (AnSBBR) using distillery wastewater as

Received in revised form

substrate at two operating pH values. Selectively enriched anaerobic mixed consortia

8 August 2007

sequentially pretreated with repeated heat-shock (100 1C; 2 h) and acid (pH 3:0; 24 h)

Accepted 5 October 2007

methods, was used as parent inoculum to startup the bioreactor. The reactor was operated

Available online 28 November 2007 Keywords: Biohydrogen Treatment Distillery wastewater Acidophilic Biofilm Periodic discontinuous/sequencing batch process Volatile fatty acids (VFA)

at ambient temperature (28  2  C) with detention time of 24 h in periodic discontinuous batch mode. Experimental data showed the feasibility of hydrogen production along with substrate degradation with distillery wastewater as substrate. The performance of the reactor was found to be dependent on the operating pH. Adopted acidophilic microenvironment (pH 6.0) favored H2 production (H2 production rate—26 mmol H2/day; specific H2 production—6.98 mol H2/kg CODR-day) over neutral microenvironment (H2 production rate—7 mmol H2/day; specific H2 production—1.63 mol H2/kg CODR-day). However, COD removal efficiency was found to be effective in operated neutral microenvironment (pH 7—69.68%; pH 6.0—56.25%). The described process documented the dual benefit of renewable energy generation in the form of H2 with simultaneous wastewater treatment utilizing it as substrate. & 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

1.

Introduction

On the background of global environmental impacts, such as greenhouse effect and resource recovery, search is going on worldwide towards non-polluting alternative fuels from renewable energy source. Due to high-energy yield (122 kJ/g) and non-polluting nature, hydrogen (H2) is considered to be a promising fuel in future [1–12]. Presently H2 is produced mainly from fossil fuels, biomass and water. About 90% of H2 is produced by the reactions of natural gas or light oil fractions with steam at high temperatures. These methods mainly consume fossil fuels as energy source and are

considered to be energy intensive and not always environment friendly. Present utilization of H2 is equivalent to 3% of the energy consumption and is expected to grow significantly in the coming years [6,7]. Biological production of H2 is one of the alternative methods where processes can be operated at ambient temperature and pressures and are less energy intensive and more environment friendly. Broadly, biological H2 production processes can be classified as biophotolysis of water using algae and cyanobacteria, photodecomposition of organic compounds by photosynthetic bacteria and fermentative H2 production from organic compounds [6–9]. Exploitation of wastewater as substrate for H2 production with

Corresponding author.

E-mail address: [email protected] (S. Venkata Mohan). 0360-3199/$ - see front matter & 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2007.10.013

ARTICLE IN PRESS I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

concurrent wastewater treatment is an attractive and effective way of tapping energy from renewable resources in a sustainable way. This provides dual environmental benefits, viz., wastewater treatment with simultaneous energy generation. Using wastewater as substrate for H2 production through anaerobic fermentation has been attracting considerable attention recently [5,7,12–19]. Distillery wastewater generated in the form of spent wash or spillage is one of the most complex and strongest industrial organic effluents. It possesses high concentration of biodegradable organic material, such as sugars, lignin, hemicelluloses, dextrin, resins and organic acids [20,21]. Molasses-based distilleries generate 8–15 l of wastewater having high chemical oxygen demand (COD) (80–160 g/l) for every litre of the alcohol produced [20]. High organic load and persistent color associated with the distillery wastewater pose serious problem to the environment and treatment of such kind of wastewater is challenging. The technologies currently used by distilleries for treatment of wastewater are biomethanation followed by two-stage biological treatment, concentration and incineration [21]. High organic load, absence of toxic chemicals and availability of large quantity of wastewater may be considered as potential sources for biohydrogen production by anaerobic fermentation. In this communication, experimental data pertaining to studies carried out on biological H2 production utilizing distillery wastewater as substrate through anaerobic fermentation in biofilm configured reactor is presented and discussed.

2.

Experimental

2.1.

Distillery wastewater

Designed synthetic wastewater (g/l; glucose—3.0, NH4Cl—0.5, KH2PO4—0.25, K2HPO4—0.25, MgCl2  6H2 O F0:3, FeCl3—0.025, NiSO4—0.016, CoCl2—0.025, ZnCl2—0.0115, CuCl2—0.0105, CaCl2—0.005 and MnCl2—0.015) and distillery wastewater were used as substrates for H2 production. The characteristics of distillery wastewaters used in the experiments are depicted in Table 1.

Table 1 – Characteristics of distillery wastewater S. No.

Characteristics

Value

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

pH Oxidation–reduction potential (ORP), mV Volatile fatty acids (VFA), mg/l Volatile suspended solids (VSS), mg/l Suspended solids (SS), mg/l Total dissolved inorganic solids (TDIS), mg/l Alkalinity, mg/l Chlorides, mg/l Sulfates, mg/l COD, mg/l BOD5 , mg/l

8.2 101 256 7600 13,500 11,600 4000 30 92 54,000 18,600

2.2.

33 (2008) 550 – 558

551

Enrichment of mixed microflora

Anaerobic sludge acquired from an operating laboratory scale upflow anaerobic sludge blanket (UASB) reactor was used as inoculum to start the reactor. Prior to inoculation, sludge was dewatered and subjected to repetitive treatment sequences (four times) altering between heat-shock treatment (100 1C; 2 h) and acid treatment (adjusted to pH 3 with orthophosphoric acid; 24 h) to inhibit the growth of methanogenic bacteria and to selectively enrich the H2-producing microflora. The resulting enriched microflora was used as inoculum for the startup of the biofilm reactor.

2.3.

Reactor configuration and operation

Bench scale anaerobic sequencing batch biofilm reactor (AnSBBR was fabricated in the laboratory using ‘perplex’ material) to operate in periodic discontinuous/sequencing batch mode. Schematic details of the experimental setup material along with AnSBBR are depicted in Fig. 1. The designed reactor consists of gas holding capacity of 0.20 l, liquid volume of 0.8 l and a working volume of 1.0 l (Table 2). The bioreactor was operated in the upflow mode (L=D ratio6) with inert stone chips (0:02 cm  0:05 cm; void ratio0:49) as fixed bed packing material for supporting the growth of mixed microflora. The reactor was fabricated using leak proof sealing material along with proper inlet and outlet arrangements. Feed was introduced from bottom of the reactor using peristaltic pump. The reactor was operated in batch mode (similar to periodic discontinuous batch mode operation) with a total cycle period of 24 h (single cycle period/hydraulic retention time, HRT) consisting of 15 min of FILL, 23 h of REACT (anaerobic), 30 min of SETTLE and 15 min of DECANT phases. At the beginning of each cycle, immediately after DECANT phase (earlier cycle), a pre-defined volume (0.8 l) was fed to the reactor during FILL phase. The reactor volume was continuously circulated with reactor outlet in closed loop at a recirculation rate (recirculation volume to feed volume ratio) of 3 during the REACT phase. The reactor was initially operated with synthetic wastewater to support biofilm formation on the supporting medium at an organic loading rate (OLR) of 2.42 kg COD/m3day by adjusting feed pH to 7. To minimize the loss of biomass during the adaptation period the reactor was initially operated at pH 7 with synthetic wastewater as substrate. Constant COD removal and biogas production (5% variation) were considered as indicators for successful formation of biofilm and subsequently the reactor was fed with distillery wastewater and operated at constant OLR of 9.6 kg COD/m3day throughout the study. Peristaltic pumps controlled by preprogrammed electronic timer (ETTS, Germany) were used to regulate the FEED, recirculation and DECANT operations. The controller was programmed to operate on a repeating 24 h cycle with a sub-program and output dedicated to the operation of each controllable element. Throughout the study, recirculation rate of 3 was maintained to achieve a homogeneous distribution of the substrate and uniform distribution of requisite consortia along the reactor depth. Feed pH was adjusted using orthophosphoric acid. Bioreactor was operated at ambient temperature of 28  2  C.

ARTICLE IN PRESS 552

I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

33 (2008) 550 – 558

HMS HS

ESP

PS PMS

D L

R L T

AnSBBR F L

PP

DWST TWST T PP Fig. 1 – (a) Schematic details of experimental setup along with anaerobic biofilm reactor (AnSBBR). AnSBBR—anaerobic sequencing batch biofilm reactor; HMS—hydrogen monitoring system; PMS—pH monitoring system; PS—pH sensor; ESP—emergency sampling point; HS—hydrogen sensor; DL—decanting loop; RL—recirculation loop; T—preprogrammed timer; PP—peristaltic pump; TWST—treated wastewater storing tank; FL—feeding loop; DWST—distillery wastewater storing tank. (b) Photograph of AnSBBR. Table 2 – Design criteria and dimensions of reactor Design flow (l/day)

0.8

Reactor volume (l), total/ working Gas holding capacity (l) Fixed film depth of reactor (cm) Void ratio of fixed bed Diameter of reactor (cm) Recirculation rate Upflow velocity at R/F 3 (cm/ day) Hydraulic loading rate (HLR) at R/F 3 [m3(liq)/m3 day] Organic load rate (OLR; kg COD/ m3-day) Single cycle period/hydraulic retention time (HRT) (h)

1/0.8

Mode of operation Reactor microenvironment/ configuration Operating temperature (1C) Feeding pH (influent)

2.4.

0.2 68 0.49 7.0 1:3 62.4 0.8 8.8 24 (single cycle period: FILL—15 min; REACT—23 h; SETTLE—30 min) Sequencing/periodic discontinuous batch mode Anaerobic/biofilm 28  2 6:0=7:0  0:1

Analysis

H2 gas generated in the bioreactor was estimated using a microprocessor based pre-calibrated H2 sensor (electrochemical 3 electrode H2 sensor, FMK satellite 4–20 mA version, ATMI GmbH Inc., Germany). The output signal displayed the % volume of H2 in the head space of the bioreactor. The

system was calibrated once in 2 days using calibration cap provided with the instrument and the sensor had a measuring range of 0.01–10% H2 with 5 s response time in a temperature range of 20–80 1C. COD (closed refluxing dichromate method), pH (LI612, ELICO, India), total alkalinity, total volatile suspended solids (VSS), volatile fatty acids (VFA), sulfates, chlorides and biochemical oxygen demand (BOD; 5 days) were determined following the standard methods [22]. The separation and quantitative determination of VFA was carried out by high performance liquid chromatography (HPLC; Shimadzu LC10A) using optimized conditions [UVVIS detector; C18 reverse phase column (250  4:6 mm; 5 m particle size), flow rate—0.5 ml/h; wavelength—210 nm; mobile phase—40% acetonitrile in 1 mN H2SO4 (pH 2.5–3.0); sample injection—20 ml]. The biofilm (pH 6.0; 144 days) formed on the stones was subjected to scanning electron microscopy (SEM). Prior to SEM imaging, samples were transferred to vials and fixed in glutaraldehyde (2.5%) in 0.05 M phosphate buffer (pH 7.2) for 24 h at 4 1C and post fixed in aqueous osmium tetroxide (2%) in the same buffer for 2 h. After the post fixation, samples were dehydrated in series of graded alcohol and scanned by SEM (JOEL-JSM 5600) after drying.

3.

Results and discussion

3.1.

Biohydrogen production

After inoculation with selectively enriched mixed consortia, the bioreactor was operated with synthetic wastewater at OLR of 2.42 kg COD/m3-day and operating pH 7. The reactor

ARTICLE IN PRESS I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

demonstrated stable performance with respect to biogas production and substrate degradation after 33 days of operation. Subsequently, the reactor was fed with distillery wastewater and operated at OLR of 9.6 kg COD/m3-day. Initially, after feeding distillery wastewater, the reactor was operated at pH 7 for a period of 34 days and subsequently changed to acidophilic pH (6.0). Experimental data documented the feasibility of molecular H2 generation along with substrate degradation from distillery wastewater during the bioreactor operation (Fig. 2). Figs. 2a and b elicit the pattern of H2 production with the function of reactor operation and cycle period, respectively. It is evident from the experimental data that the operating pH had shown considerable influence on the H2 generation efficiency and substrate degradation rate (SDR). At operating pH 7.0, the system showed cumulative H2 production of 7 mmol H2/day at the end of the cycle period of 20 days of feeding the wastewater (Fig. 2a). During this phase of stable operation, the reactor also showed a maximum specific H2 production of 1.63 mol H2/kg CODR-day. At operating pH 6.0, the reactor responded positively with significant enhancement in H2 production. A gradual rise in cumulative H2 production was observed and approached a maximum of 26 mmol H2/day after 91 days of changing the operating pH to 6. The variation of volumetric H2 production and specific H2 production during sequence phase operation with the function of time is depicted in Fig. 2b. The system registered a maximum specific H2 production of 6.985 mol H2/ kg CODR-day. H2 production with respect to single cycle period showed a distinct trend (Fig. 2b). A consistent increase in volumetric H2 production was observed with time. Maximum volumetric production (210.02 mol H2/m3-day) was registered after 14th hour of cycle operation and a gradual drop in production was observed, thereafter, prior to stabilizing at 165.81 mol H2/m3-day at the end of cycle period. Specific H2 production also followed more or less similar pattern with volumetric production of H2 registering maximum yield after 14 h of cycle operation (18.69 mol H2/kg CODR-day) during stabilized phase of operation. Experimental data evidenced the positive influence of acidophilic conditions (pH 6) on the H2 production. One of the effective ways to enhance H2 production from the anaerobic culture is to restrict or terminate the methanogenesis process by allowing H2 to become an end product in the metabolic flow. A pH range of 5.5–6 was reported to be ideal to avoid both methanogenesis and solventogenesis [25,26] and could be considered the optimum pH range for effective H2 generation. Anaerobic cultures could generate H2 as metabolic intermediate at operating acidic pH where acidogenic bacteria are active. Conversion efficiency of H2 was reported to increase by maintaining the operating pH around 6 (optimum being pH 5.5–6.0) compared to a near neutral pH [23,24,27–31]. Optimum pH for methanogenic bacteria was between 6.0 and 7.5 [32,33], while acidogenic bacteria functioned well below 6 pH. Lower operating pH inhibits methanogenic bacteria and maintains acidogenic bacteria activity [23,27–29,34–37]. Adopted acidophilic operating conditions can be considered to be favorable microenvironment for the effective specific H2 production by inhibiting the methanogenic group of bacteria and providing congenial conditions for the acidogenic bacteria to function. Ren et al.

33 (2008) 550 – 558

553

[36] evaluated biohydrogen production in a continuous flow anaerobic fermentation pilot scale reactor from molasses and reported a maximum volumetric production rate of 5.57 m3 H2/m3-day with a specific production rate of 0.75 m3 H2/kg MLVSS-day.

3.2.

Wastewater treatment

The performance of bioreactor was also evaluated for substrate removal efficiency (as SDR) during H2 production with the function of reactor operation (Fig. 2c). The substrate pattern was evaluated by estimating the substrate (COD) removal efficiency (xCOD ) using Eq. (1), where CSO represents the initial COD concentration (mg/l) in the feed and CS denotes COD concentration (mg/l) in the reactor outlet. xCOD ¼ ½ðCSO  CS Þ=CSO .

(1)

OLR (kg COD/m3-day) was calculated using Eq. (2), where FR represents feed rate (m3/day) and Rv denotes reactor volume (m3). OLR ¼ f½COD0  FR =Rv g.

(2)

3

SDR (kg COD/m -day) was calculated to study the rate and pattern of COD removal with time according to Eq. (3), where COD0 and CODT represent COD (mg/l) at ‘0’ and ‘T’ times, respectively. SDR ¼ f½ðCOD0  CODT Þ  FR =Rv g.

(3)

The bioreactor documented potential for substrate removal in concurrence with H2 production. It is evident from the substrate degradation pattern observed that the distillery wastewater was consumed in the metabolic reactions as primary carbon source involving molecular H2 generation. However, substrate degradation efficiency was found to be dependent on the operating pH. This may be attributed to the consequence of methanogenic activity inhibition generally occurred at acidophilic conditions. At operating pH of 7.0, the system documented COD removal efficiency between 19.8% and 69.68% accounting for SDR of 1.92–6.69 kg COD/m3-day. Initially, after feeding the distillery wastewater, the reactor yielded relatively lower SDR (1.92 kg COD/m3-day; 36 days after startup), which rapidly approached a maximum on 41 day (6.4 kg COD/m3-day) after startup prior to stabilization. After shifting the reactor operating pH to 6 a significant reduction in the COD removal efficiency was observed. During this phase of operation, the COD removal efficiency varied between 29.06% and 56.25% accounting for SDR of 2.79–5.4 kg COD/m3-day. The reactor stabilized with respect to substrate removal after 148 days after startup at SDR of 4.6 kg COD/m3-day. A marked reduction in COD removal efficiency was observed at acidophilic conditions compared to neutral operating conditions. Higher substrate degradation efficiency observed at 7 pH may be attributed to the prevalence of associated methanogenic bacterial activity. A relatively good correlation was observed at pH 6.0 (R2 F0:383) than pH 7.0 (R2 F0:0483) when substrate degradation was correlated with H2 production. This is indicative of the importance of operating pH with respect to H2 production process.

ARTICLE IN PRESS I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

33 (2008) 550 – 558

30

8 pH 6

pH 7 Specific H2 production (mol H2/kg CODR-day)

7

25

6 20

5

15

4 3

10

2 5

1

Cumulative H2 Production (mmol H2 /day)

554

0

0 34

40

47

59

69

84

93

115

126

144

161

181

Time (days)

250

20

16

150

12

100

8

50

4

0

Specific H2 production (mol H2/Kg CODR-day)

Volumetric H2 production (mol H2/m3-day)

pH 6 200

0 0

0.5

1

2

4

6 8 Time (h)

10

14

16

20

24

SDR (Kg COD/m3-day)

6

4

2

pH 7

pH 6

0 30

50

70

90

110 130 Time (days)

150

170

190

Fig. 2 – (a) Performance of AnSBBR with respect to H2 production during operation (operating pH—7.0/6.0; total operation time of reactor including adaptation phase—181 days). (b) Volumetric H2 production and specific H2 production during sequence phase operation [operating pH—6.0; retention time of cycle (single)—24 h]. (c) Substrate degradation rate (SDR) during reactor operation (operating pH—7.0/6.0; total operation time of reactor including adaptation phase—181 days).

3.3.

Bioprocess monitoring

VFA, pH and alkalinity were also monitored during the bioreactor operation to assess the bioprocess mechanism

during H2 production (Fig. 3). H2 production is generally accompanied by acid and solvent production due to acidogenic metabolism. Acidic intermediates formed during the process generally reflect changes in the metabolic pathway of

ARTICLE IN PRESS I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

555

33 (2008) 550 – 558

10000

5000 pH 6

8000

4000

6000

3000

4000

2000

2000

1000

0

Alkalinity (Outlet) (mg/l)

VFA (Outlet) (mg/l)

pH 7

0 34

39

43

56

59

67

74

86

93 112 119 131 144 158 176

Time (days)

8 pH 7

pH 6

pH (outlet)

7

6

5

4 30

50

70

90

110

130

150

170

190

Time (days) 5000

6.6 pH 6

4000

3000 5.8 2000

Reactor VFA (mg/l)

Reactor pH

6.2

5.4 1000

5

0 0

0.5

1

2

4

6

8

10

14

16

20

24

Time (h) Fig. 3 – (a) Variation of volatile fatty acids (VFA) (outlet) and alkalinity (outlet) during AnSBBR operation (operating pH—7.0/6.0; total operation time of reactor including adaptation phase—181 days). (b) Variation in outlet pH during AnSBBR operation (operating pH—7.0/6.0; total operation time of reactor including adaptation phase—181 days). (c) Variation in VFA and pH during sequence phase operation [operating pH—6.0; retention time of cycle (single)—24 h].

ARTICLE IN PRESS 556

I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

the microorganisms and provide a better insight which could be used to improve the conditions favorable for H2 production. Fig. 3a illustrates variation in VFA and alkalinity during the bioreactor operation. VFA production was always associated with conversion of organic fraction to acid intermediates in the anaerobic microenvironment with the help of specific group of bacteria and represents total of all acids generated during the acidogenic fermentation step. VFA production showed a consistent variation with the function of operating pH. Maximum VFA production (7851 mg/l) was observed at operating pH 6.0 compared to operating pH 7.0 (5639 mg/l). High VFA yield observed at operating pH 6.0 might be attributed to the prevailing acidophilic conditions, which inhibited the methanogenic activity required for VFA breakdown. Alkalinity in anaerobic microenvironment was considered as an index of volatile acid generation in alliance with the existing buffering capacity (alkalinity) of the system. Inconsistent variation in the concentration of alkalinity was observed at operating pH 7.0. However, at operating pH 6.0, relatively stabilized values were observed throughout the operation between 500 and 1000 mg/l. The distribution of metabolites formed during H2 fermentation was crucial in assessing the H2-producing cultures efficiency [17,18,37–39] and provide better understanding of the change in the metabolic pathway. Reactor samples during the course of experiments were collected and analyzed for the composition of VFA. Chromatographic analysis of samples, showed presence of higher concentration of acetic acid and relatively lower concentration of butyric acid. This suggests that the acid-forming pathway dominated the metabolic flow during H2 generation with the occurrence of acidogenesis instead of solventogenesis. It is reported that high specific H2 production was associated with a mixture of acetate and butyrate fermentation products, and low specific H2 production was observed with propionate and reduced end products (alcohols, lactic acid) [9]. This phenomena observed in the reactor under acidophilic conditions could be considered as the optimum environment for effective H2 generation. The variation in outlet pH was documented in Fig. 3b and variation of pH during sequence phase operation is depicted in Fig. 3c. A relatively basic value of pH (near 7) was observed at operating pH 7. While at operating pH 6.0, the system registered outlet pH between 5 and 7. Production of acids and its accumulation showed a gradual reduction in buffering capacity (total alkalinity) that resulted in a concomitant decline in the system pH. However, at operating pH 7 due to the persistence of methanogenic bacteria, VFA consumption takes place resulting in basic pH. VFA showed almost similar correlation with outlet pH with both the operating pH studied [R2 F0:342 (pH 6.0); R2 F0:331 (pH 7.0)]. SEM (5:0 K; Fig. 4) of biofilm (pH 6.0; 144 days) acquired from the stone chips showed an image of morphologically similar bacterial groups (predominant short rod; 10220 mm in length). Images of mixed consortia visualized morphological similarities indicating related group of bacteria proliferating in the biofilm reactor producing H2. The selective enrichment procedure adopted in this study might result in enrichment of specific group of rod shaped bacteria which is capable of producing H2. Use of mixed microbial cultures is considered

33 (2008) 550 – 558

Fig. 4 – Scanning electron micrograph (SEM; 5:0 K) of biofilm (operating pH 6.0; biofilm sampled on 148 days of operation).

to be a practical, cost-effective and promising approach to achieve H2 production in large scale. The reactor configuration in addition to operating pH used may also have considerable influence on the H2 evolution. Bacteria capable of decomposing xenobiotic compounds generally had a comparatively low growth rate and are especially observed where slowly growing organisms with special metabolic capacities are to be protected from washout. Biofilm reactor configuration coupled with batch mode operation, maintained high biomass concentration, resulting in the enrichment of slow growing organisms; this phenomenon lead to homogeneous biomass distribution throughout the reactor [40,41]. The biofilm configured systems are less energy intensive and more resistant to change in the process parameters [41,42].

4.

Conclusions

This study demonstrated the feasibility of biological hydrogen generation from distillery wastewater treatment in biofilm reactor using selective enriched anaerobic mixed inoculum. Adopted operation conditions such as acidophilic condition (operating pH 6.0), selective enrichment of parent inoculum, biofilm configuration and periodic discontinuous batch mode operation documented a positive influence on the overall H2 production and substrate degradation. Integration of biofilm configuration with batch mode operation is considered to be highly flexible and has potential to provide the possibility of influencing the microbial system by selectively enriching specific group of microflora.

Acknowledgments The authors gratefully acknowledge the financial support from Department of Biotechnology (DBT), Government of India in the form of project (BT/PR/4405/BCE/08/312/2003) for carrying out this research work.

ARTICLE IN PRESS I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

R E F E R E N C E S

[20] [1] Hart DD. Hydrogen power: the commercial future of the ‘‘ultimate fuel’’. London: Financial Times Energy Publishing; 1997. [2] Lay JJ, Li YY, Noike T. A mathematical model for methane production from landfill bioreactor. J Environ Eng ASCE 1998;124:730–6. [3] Pinto FAL, Troshina O, Lindblad P. A brief look at three decades of research on cyanobacterial hydrogen evolution. Int J Hydrogen Energy 2002;27:1209–15. [4] Fan YT, Li CL, Lay JJ, Hou HH, Zhang GSh. Optimization of initial substrate and pH levels for germination of sporing hydrogen producing anaerobes in cow dung compost. Bioresource Technol 2004;91:189–93. [5] Lin CY, Lay CH. Carbon/nitrogen-ratio effect on fermentative hydrogen production by mixed microflora. Int J Hydrogen Energy 2004;29:41–5. [6] Das D, Veziroglu TN. Hydrogen production by biological process: a survey of literature. Int J Hydrogen Energy 2001;26:13–28. [7] Logan BE. Biologically extracting energy from wastewater: biohydrogen production and microbial fuel cells. Environ Sci Technol 2004;38:160A–7A. [8] Levin DB, Pitt L, Love M. Biohydrogen production: prospects and limitations to practical application. Int J Hydrogen Energy 2004;29:173–85. [9] Hawkes FR, Dinsdale R, Hawkes DL, Hussy I. Sustainable fermentative hydrogen production: challenges for process optimisation. Int J Hydrogen Energy 2002;27:1339–47. [10] Yu H, Zhu Z, Hu W, Zhang H. Hydrogen production from rice winery wastewater in an upflow anaerobic reactor by using mixed anaerobic cultures. Int J Hydrogen Energy 2002;27:1359–65. [11] Atif AAY, Razia AF, Ngan MA, Morimoto M, Iyukec SE, Veziroglu NT. Fed batch production of hydrogen from palm oil mill effluent using anaerobic microflora. Water Sci Technol 2005;53:271–9. [12] Ginkel SWV, Oh SE, Logan BE. Biohydrogen gas production from food processing and domestic wastewaters. Int J Hydrogen Energy 2005;30:1535–42. [13] Fan YT, Zhang YH, Zhang SF, Hou HW, Ren BZ. Efficient conversion of wheat straw wastes into biohydrogen gas by cow dung compost. Bioresource Technol 2006;97:500–5. [14] Vijayaraghavan K, Ahmad D, Ibrahim MKB. Biohydrogen generation from jackfruit peel using anaerobic contact filter. Int J Hydrogen Energy 2006;31:569–79. [15] Yang H, Shao P, Lub T, Shena J, Wang D, Xub Z, et al. Continuous bio-hydrogen production from citric acid wastewater via facultative anaerobic bacteria. Int J Hydrogen Energy 2006;31:1306–13. [16] Venkata Mohan S, Lalit Babu V, Sarma PN. Effect of various pretreatment methods on anaerobic mixed microflora to enhance biohydrogen production utilizing dairy wastewater as substrate. Bioresource Technol 2008;99(1):59–67. [17] Venkata Mohan S, Vijaya Bhaskar Y, Sarma PN. Biohydrogen production from chemical wastewater treatment by selectively enriched anaerobic mixed consortia in biofilm configured reactor operated in periodic discontinuous batch mode. Water Res 2007;41:2652–64. [18] Venkata Mohan S, Lalit Babu V, Sarma PN. Anaerobic biohydrogen production from dairy wastewater treatment in sequencing batch reactor (AnSBR): effect of organic loading rate. Enzyme Microbial Technol 2007;41(4):506–15. [19] Venkata Mohan S, Veer Raghuvulu S, Srikanth S, Sarma PN. Bioelectricity production by meditorless microbial fuel cell (MFC) under acidophilic condition using wastewater as

[21]

[22]

[23]

[24]

[25]

[26] [27]

[28]

[29]

[30]

[31]

[32]

[33]

[34]

[35]

[36]

[37]

33 (2008) 550 – 558

557

substrate: influence of substrate loading rate. Curr Res 2007;92(12):1720–6. Ali S. Move towards a zero liquid discharge distillery. In: Proceedings of the second FICCI-TERI global conference: Green–2002 Agenda for Industry, 7–8 February, New Delhi, India, 2002. Tapas N, Sunita S, Kaul SN. Wastewater management in a cane molasses distillery involving bioresource recovery. J Environ Manage 2002;65:25–38. APHA. Standard methods for the examination of water and wastewater. In: 20th, American Public Health Association, American Water Works Association, Water Pollution Control Federation, Washington, DC, 1998. Fang HHP, Liu H. Effect of pH on hydrogen production from glucose by a mixed culture. Bioresource Technol 2002;82:87–93. Rogers O. Genetics and biochemistry of clostridium relevant to development of fermentation process. Appl Microbiol 1984;31:1–60. Ginkel SV, Lay JJ, Sung S. Biohydrogen production as a function of pH and substrate concentration. Environ Sci Technol 2001;35:4726–30. Ginkel SV, Logan B. Increased biological hydrogen production with reduced organic loading. Water Res 2005;39:3819–26. Venkata Mohan S, Bhaskar YV, Krishna TM, Chandrasekhara Rao N, Lalit Babu V, Sarma PN. Biohydrogen production from chemical wastewater as substrate by selectively enriched anaerobic mixed consortia: influence of fermentation pH and substrate composition. Int J Hydrogen Energy 2007;32(13):2286–95. Venkata Mohan S, Mohanakrishna G, Purushotam Reddy B, Sarvanan R, Sarma PN. Bioelectricity generation from chemical wastewater treatment in mediatorless (anode) microbial fuel cell (MFC) using selectively enriched hydrogen producing mixed culture under acidophilic microenvironment. Biochemical Engineering Journal, doi:10.1016/ j.bej.2007.08.023. Venkata Mohan S, Mohanakrishna G, Veer Raghuvulu S, Sarma PN. Enhancing biohydrogen production from chemical wastewater treatment in anaerobic sequencing batch biofilm reactor (AnSBBR) by bioaugmenting with selectively enriched kanamycin resistant anaerobic mixed consortia. Int J Hydrogen Energy 2007;32(15):3284–92. Liu Y, Boone DR, Sleat R, Mah RA. Methanosarcina mazei LYC—a new methanogenic isolate which produces a disaggregating enzyme. Appl Environ Microbiol 1985;57: 2104–8. Boopathy R, Daniels L. Effect of pH on anaerobic mild steel corrosion by methanogenic bacteria. Appl Environ Microbiol 1991;57:2104–8. Oh SE, Van Ginkel S, Logan BE. The relative effectiveness of pH control and heat treatment for enhancing biohydrogen gas production. Environ Sci Technol 2003;37:5186–90. Lin CY, Chen CC, Lin MC. Hydrogen production in anaerobic acidogenesis process—influences of thermal isolation and acclimation environment. J Chin Inst Environ Eng 2000;10:163–8. Logan BE, Oh SE, Ginkel SV, Kim IS. Biological hydrogen production measured in batch anaerobic respirometers. Environ Sci Technol 2002;36:2530–5. Ferchichi M, Crabbe E, Gil G, Hintz W, Almadidy A. Influence of initial pH on hydrogen production from cheese whey. J Biotechnol 2005;20:402–9. Ren N, Li J, Li B, Wang Y, Liu S. Biohydrogen production from molasses by anaerobic fermentation with a pilot-scale bioreactor system. Int J Hydrogen Energy 2006;31:2147–57. Cha GC, Noike T. Effect of rapid temperature and HRT on anaerobic acidogenesis. Water Sci Technol 1997;36:247–53.

ARTICLE IN PRESS 558

I N T E R N AT I O N A L J O U R N A L O F H Y D R O G E N E N E R G Y

[38] Dinopoulou G, Rudd T, Lester JN. Anaerobic acidogenesis of complex wastewater. The influence of operational parameters on reactor performance. Biotechnol Bioeng 1998;31:958–68. [39] Lee YJ, Miyahara T, Noike T. Effect of pH on the microbial hydrogen fermentation. In: Proceedings of 6th IAWQ AsianPacific conference, Taipei; 1999. p. 215–20. [40] Kaballo HP, Zahao Y, Wilderer PA. Elimination of p-chlorophenol in biofilm reactor—a comparative study of continu-

33 (2008) 550 – 558

ous flow and sequenced batch operation. Water Sci Technol 1995;33:51–60. [41] Venkata Mohan S, Chandrasekhar Rao N, Sarma PN. Composite chemical wastewater treatment by biofilm configured periodic discontinuous batch reactor operated in anaerobic metabolic function. Enzyme Microbial Technol 40(5), 1398–406. [42] Chaudhry MRS, Beg SA. A review on the mathematical modeling of biofilm processes: advances in fundamentals of biofilm modeling. Chem Eng Technol 1998;21:701–10.