Optimization of conditions for hydrogen production from complex dairy wastewater by anaerobic sludge using desirability function approach

Present study deals with the multiple-response optimization for biohydrogen production using anaerobic sludge and outstanding approach to overcome the drawbacks of conventional response surface methodology (RSM). Dairy wastewater was used as source in batch fermentation was followed for this study. Response surface methodology (RSM), based on a three level, four variable Box–Behnken design, was employed to obtain the best possible combination of substrate concentration, pH, COD/N ratio and COD/P ratio for maximum H₂ yield (HY) and specific hydrogen production rate (SHPR). Experimental data were evaluated by applying RSM integrating a desirability function approach. The optimum H₂ yield and SHPR conditions were: substrate concentration 15.3 g COD/L, pH 5.5, COD/N ratio 100.5 and COD/P ratio 120 with maximum overall desirability D of 0.94. The confirmation experiment under these optimal condition showed a HY and SHPR of 13.54 mmol H₂/g COD and 29.91 mmol H₂/g-VSS.d, respectively. This was only 0.22% and 0.20%, respectively, different from the predicted values, suggesting that the desirability function approach with RSM was a useful technique to get the maximum H₂ yield and SHPR simultaneously.     

Hydrogen production from alcohol distillery wastewater containing high potassium and sulfate using an anaerobic sequencing batch reactor

In this study, the feasibility of hydrogen production from alcohol distillery wastewater containing high potassium and sulfate was investigated using an anaerobic sequencing batch reactor (ASBR). The seed sludge taken from an anaerobic tank treating the distillery wastewater was boiled for 15 min before being fed to the ASBR. The ASBR system was operated under different feed chemical oxygen demand (COD) values and different COD loading rates at a mesophilic temperature of 37 °C, a controlled pH at 5.5, and a cycle time of 6 cycles per day. When the studied ASBR was operated under the best conditions (providing a maximum hydrogen production efficiency) of a feed COD of 40,000 mg/l, a COD loading rate of 60 kg/m³ d, and a hydraulic retention time of 16 h, the produced gas was found to contain 34.7% H₂ and 65.3% CO_2, without any methane being detected. Under these best conditions, the specific hydrogen production rate (SHPR) of 270 ml H₂/g MLVSS d (or 3310 ml H₂/l d), and hydrogen yield of 172 ml H₂/g COD removed, were obtained. When the feed COD exceeded 40,000 mg/l, the process performance in terms of hydrogen production decreased because of the potassium and sulfate toxicity.     

Hydrogen production from cassava wastewater using an anaerobic sequencing batch reactor: Effects of operational parameters,COD:N ratio,and organic acid composition

In this work, hydrogen production from cassava wastewater using anaerobic sequencing batch reactors (ASBR) was investigated to determine the optimum number of cycles per day, chemical oxygen demand (COD) loading rate, and COD:N ratio. The system operated at a COD loading rate of 30 kg/m³d and 6 cycles per day provided maximum hydrogen production performance in terms of specific hydrogen production rate (SHPR) (388 ml H₂/g VSS d or 3800 ml H₂/l d) and hydrogen yield (186 ml H₂/g COD removed). The effect of nitrogen supplementation was also studied by adding NH₄HCO₃ into the system at the COD:N ratios of 100:2.2, 100:3.3, and 100:4.4 under the COD loading rate of 30 kg/m³d and 6 cycles per day. The maximum SHPR and hydrogen yield of 524 ml H₂/g VSS d (5680 ml H₂/l d) and 438 ml H₂/g COD removed, respectively, were obtained at the stoichiometric COD:N ratio of 100:2.2. An excess nitrogen was found to promote the productions of higher organic acids and ethanol, resulting in lowering hydrogen production efficiency.     

Optimization of key factors affecting hydrogen production from food waste by anaerobic mixed cultures

Key factors (inoculums concentration, substrate concentration and citrate buffer concentration) affecting hydrogen yield (HY) and specific hydrogen production rate (SHPR) from food waste in batch fermentation by anaerobic mixed cultures were optimized using Response Surface Methodology with Central Composite Design. The experiments were conducted in 120 ml serum bottles with a working volume of 70 mL. Under the optimal condition of 2.30 g-VSS/L of inoculums concentration, 2.54 g-VS/L of substrate concentration, and 0.11 M of citrate buffer concentration, the predicted maximum HY and SHPR of 104.79 mL H₂/g-VS_added and 16.90 mL H₂/g-VSS.h, respectively, were obtained. Concentrations of inoculums, substrate and citrate buffer all had an individual effect on HY and SHPR (P < 0.05). The substrate concentration and citrate buffer concentration had the greatest interactive effect on SHPR (P = 0.0075) while their effects on HY (P = 0.0131) were profound. These results were reproduced in confirmation experiments under optimal conditions and generated an HY of 104.58 mL H₂/g-VS_added and an SHPR of 16.86 mL H₂/g-VSS.h. This was only 0.20% and 0.24%, respectively, different from the predicted values. Microbial community analysis by PCR-DGGE indicated that Clostridium was the pre-dominant hydrogen producer at the optimum and worst conditions. The presence of Lactobacillus sp. and Enterococcus sp. might be responsible for the low HY and SHPR at the worst condition.     

Fermentative production of hydrogen from cassava processing wastewater by Clostridium acetobutylicum

This work reports on the effect of initial substrate concentration on COD consumption, pH, and H₂ production during cassava processing wastewater fermentation by Clostridium acetobutylicum ATCC 824. Five initial COD wastewater concentrations, namely 5.0, 7.5, 10.7, 15.0, and 30.0 g/L, were used. The results showed that higher substrate concentrations (30.0 and 15.0 COD/L) led to lower H₂ yield as well as less efficient substrate conversion into H₂. On the other hand, initial COD concentrations of 10.7, 7.5 and 5 g/L furnished 1.34, 1.2 and 2.41 mol H₂/mol glucose, with efficiency of glucose conversion into H₂ of 34, 30, and 60% (mol/mol), respectively. These results demonstrate that cassava processing wastewater, a highly polluting effluent, can be successfully employed as substrate for H₂ production by C. acetobutylicum at lower COD concentrations.     

Lactate wastewater dark fermentation: The effect of temperature and initial pH on biohydrogen production and microbial community

Biohydrogen production using dark fermentation (hydrolysis and acidogenesis) is one of the ways to recover energy from lactate wastewater from the food-processing industry, which has high organic matter. Dark fermentation can be affected by the temperature, pH and the microbial community structure. This study investigated the effects of temperature and initial pH on the biohydrogen production and the microbial community from a lactate wastewater using dark fermentation. Biohydrogen production was successful only at lower temperature levels (35 and 45 °C) and initial pH 6.5, 7.5 and 8.5. The highest hydrogen yield (0.85 mol H₂/mol lactate consumed) was achieved at 45 °C and initial pH 8.5. The COD reduction achieved by fermenting the lactate wastewater at 35 °C ranged between 21 and 30% with the maximum COD reduction at pH 8.5, and at 45 °C, the COD reduction ranged between 12 and 21%, with the maximum at pH 7.5. At 35 °C, the lactate degradation ranged between 54 and 95%, while at 45 °C, it ranged between 77 and 99.8%. 16S rRNA sequencing revealed that at 35 °C, bacteria from the Clostridium genera were the most abundant at the end of the fermentation in the reactors that produced hydrogen, while at 45 °C Sporanaerobacter, Clostridium and Pseudomonas were the most abundant.     

Effects of biomass,COD and bicarbonate concentrations on fermentative hydrogen production from POME by granulated sludge in a batch culture

Effects of three selected variables viz. biomass concentration, initial chemical oxygen demand (COD) concentration and initial bicarbonate alkalinity (BA) on biological hydrogen production from palm oil mill effluent (POME) using the granulated sludge in batch culture were investigated. The experimental results were analyzed and modeled using a central composite design (CCD) of response surface methodology (RSM). In order to carry out a comprehensive analysis of the biohydrogen production process, indicative parameters namely hydrogen yield (Y_H), specific hydrogen production rate (SHPR), and COD removal efficiency were studied as the process responses. Maximum hydrogen yield (124.5 mmol H₂/g COD_removed) and specific hydrogen production rate (55.42 mmol H₂/g VSS.d) were achieved at COD_in 3000 and 6500 mg/l, MLVSS 4000 and 2000 mg/l, and initial BA 1100 mg CaCO₃/l, respectively.     

Optimization of biohydrogen production of palm oil mill effluent by ozone pretreatment

The biohydrogen (H₂) production in batch experiments under varying concentrations of raw and ozonated palm oil mill effluent (POME) of 5000–30,000 mg COD.L⁻¹, at initial pH 6, under mesophilic (37 °C), thermophilic (55 °C) and extreme-thermophilic (70 °C) conditions. Effects of ozone pretreatment, substrate concentration and fermentation temperature on H₂ production using mesophilic seed sludge was undertaken. The results demonstrated that H₂ can be produced from both raw and ozonated POME, and the amounts of H₂ production were directly increased as the POME concentrations were increased. H₂ was successfully produced under the mesophilic fermentation of ozonated POME, with maximum H₂ yield, and specific H₂ production rate of 182 mL.g⁻¹ COD_removed (30,000 mg COD.L⁻¹) and 6.2 mL.h⁻¹.g⁻¹ TVS (25,000 mg COD.L⁻¹), respectively. Thus, indicating that the ozone pretreatment could elevate on the biodegradability of major constituents of the POME, which significantly enhanced yields and rates of the H₂ production. H₂ production was not achieved under the thermophilic and extreme-thermophilic fermentation. In both fermentation temperatures with ozonated POME, the maximum H₂ yield was 62 mL.g⁻¹ COD_removed (30,000 mg COD.L⁻¹) and 63 mL.g⁻¹ COD_removed (30,000 mg COD.L⁻¹), respectively. The highest efficiency of total and soluble COD removal was obtained at 44 and 37%, respectively following the mesophilic fermentation, of 24 and 25%, respectively under the thermophilic fermentation, of 32 and 20%, respectively under the extreme-thermophilic fermentation. The production of volatile fatty acids increased with an increased fermentation time and temperature in both raw and ozonated POME under all three fermentation temperatures. The accumulation of volatile fatty acids in the reactor content were mostly acetic and butyric acids. H₂ fermentation under the mesophilic condition of 37 °C was the better selection than that of the thermophilic and extreme-thermophilic fermentation.     

Enhancement effect of zero-valent iron nanoparticle and iron oxide nanoparticles on dark fermentative hydrogen production from molasses-based distillery wastewater

This study investigates the effect of two different iron compounds (zero-valent iron nanoparticle: nZVI and iron oxide nanoparticles: nIO) and pH on fermentative biohydrogen production from molasses-based distillery wastewater. The nZVI and nIO of optimum particle sizes of 50 nm and 55 nm respectively were synthesized and applied for fermentative hydrogen (H₂) production. The addition of nIO & nZVI at (0.7 g/L, pH: 6) resulted in the highest H₂ yield, H₂ production rate, H₂ content and COD reduction. Moreover, the kinetic parameters of H₂ production potential (P) and H₂ production rate (R_m) increased to 387 mL, and 22.2 mL/h, respectively for nZVI, these values were 363 mL and 21.8 mL/h for nIO. The results obtained indicated the positive effect of nZVI and nIO addition on enhanced fermentative H₂ production. The addition of nZVI & nIO resulted in 71% and 69.4% enhancement in biohydrogen production respectively.     

Hydrogen gas production from vinegar fermentation wastewater by electro-hydrolysis: Effects of initial COD content

Vinegar fermentation wastewater with different initial COD contents (9.66–48.6 g L⁻¹) were used for hydrogen gas production with simultaneous COD removal by electro-hydrolysis. The applied DC voltage was constant at 4 V. The highest cumulative hydrogen production (3197 ml), hydrogen yield (2766 ml H₂ g⁻¹ COD), hydrogen formation rate (799 ml d⁻¹), and percent hydrogen (99.5%) in the gas phase were obtained with the highest initial COD of 48.6 g COD L⁻¹. The highest energy efficiency (48%) was obtained with the lowest COD content of 9.66 g L⁻¹. Hydrogen gas production by water electrolysis was less than 250 ml and wastewater control resulted in less than 25 ml H₂ in 96 h. The highest (12%) percent COD removal was obtained with the lowest COD content. Hydrogen gas was produced by reaction of (H⁺) ions present in raw WW ( pH = 3.0) and protons released from acetic acid with electrons provided by electrical current. Electro-hydrolysis of vinegar wastewater was proven to be an effective method of H₂ gas production with some COD removal.     

Dark fermentative hydrogen production from simple sugars and various wastewaters by a newly isolated Thermoanaerobacterium thermosaccharolyticum SP-H2

The hydrogen-producing bacterium SP-H2 was isolated from a thermophilic acidogenic reactor inoculated with municipal sewage sludge and processing a carbohydrate-rich simulated food waste. Based on the 16S rRNA gene sequence, the bacterium was identified as Thermoanaerobacterium thermosaccharolyticum. The maximum growth rate was observed at 55–60 °C and pH 7.5. The H₂-producing activity of the bacterium was studied using mono-, di- and tri-saccharides related to both hexoses (maltose, glucose, mannose, fructose, lactose, galactose, sucrose, raffinose, cellobiose) and pentoses (xylose and arabinose), as well as using real wastewaters (cheese whey, confectionery wastewater, sugar-beet processing wastewater). The highest H₂ yield was observed during dark fermentation (DF) of maltose (1.91 mol H₂/mol hexose or 77.8 mmol H₂/L). The maximum H₂ production rate was observed during DF of xylose (13.3 ml H₂/g COD/h) and cellobiose (2.47 mmol H₂/L/h). The main soluble metabolite products were acetate, ethanol and butyrate. The acetate concentration had a statistically significant positive correlation with the H₂ content in biogas and the specific H₂ yield. Based on the results of the correlation analysis, it was tentatively assumed that in the formic acid (mixed-acid) type fermentation, the rate of H₂ production was higher than in the butyric acid type fermentation. With regard to real wastewater, cheese whey and confectionery wastewater were distinguished by a higher H₂ yield (152 ml H₂/g COD) and H₂ production rate (0.57 mmol H₂/L/h), respectively. The highest concentrations of confectionery wastewater and cheese whey, at which the DF process took place, were 5915 and 7311 mg COD/L, respectively. At the same time, SP-H2 dominated in the microbial community, despite the presence of indigenous microorganisms in wastewater. Thus, T. thermosaccharolyticum SP-H2 is a promising strain for DF of carbohydrate-rich unsterile wastewater under thermophilic conditions.     

Characteristics of biohydrogen fermentation from various substrates

The characteristics of biohydrogen production from sucrose, slurry-type piggery waste and food waste under the effects of the reactor configurations and operational pHs (6 and 9) were examined by using heat-treated anaerobic sludge as a seed biomass. When sucrose was used in the batch test, the maximum hydrogen yield was 0.12–0.13 g COD (as H₂)/g COD (1.41–1.43 mol/mol hexose) at pH 6. In contrast, 0.10–0.11 g COD (as H₂)/g COD (1.12–1.21 mol/mol hexose) hydrogen yield was achieved from the reactor at pH 9. On the other hand, hydrogen production was not observed in the continuous sequencing batch mode fermenters fed with sucrose. Profile analysis at each cycle revealed hydrogen production at the initial operation periods but eventually only methane at 36 days. When slurry-type piggery waste was used as the substrate, the upflow elutriation-type fermenters produced methane but not hydrogen after 30 days operation. The fermentation intermediate profile showed that the hydrogen produced might have been consumed by homoacetogenic or propionate producing reactions, and eventually converted into methane by acetoclastic methanogens. The downflow leaching bed fermenters using food waste produced 0.013 L H₂/g volatile solids (VS) (0.0061 g COD (as H₂)/g COD) at pH 6 with 54% VS reduction whereas 0.0041 L H₂/g VS (0.0020 g COD (as H₂)/g COD) was produced at pH 9 with 86% VS reduction. The results show that the hydrogen produced should be released rapidly from the reactor before it can be consumed in other biochemical reactions, and substrates with high pH level (>9.0) can be used directly to produce hydrogen without needing to adjust the pH.     

Optimization of conditions for hydrogen production from brewery wastewater by anaerobic sludge using desirability function approach

Brewery wastewater was converted H₂ by anaerobic sludge in batch experiments. A three-factor three-level experimental design of Box-Behnken method was adopted to find the optimum H₂ production conditions. The effects of three major influence factors, temperature, pH and brewery wastewater concentration (BWC), on H₂ yield and H₂ maximum production rate (R_max) were evaluated by applying response surface methodology (RSM) integrating a desirability function approach. Desirable H₂ yield and R_max simultaneously were achieved under temperature 35.9 °C, pH 5.95 and BWC 6.05 g/l by a desirability function approach which produced the maximum overall desirability 0.894. Correspondingly, the H₂ yield and R_max were 149.6 ml H₂/g COD and 53.6 ml/h, respectively. The verification test confirms that the optimum H₂ yield and R_max measured were in good agreement with the predicted values, suggesting that the desirability function approach with RSM was a useful technique to get the maximum H₂ yield and R_max simultaneously.     

Ozonation aided mesophilic biohydrogen production from palm oil mill effluent

Ozone pretreatment of palm oil mill effluent (POME) was employed to improve sustrate biodegradability prior to biological H₂ production. The H₂ production was conducted at varing pHs from 4.0 to 6.0 to examine the impact of pH on the H₂ mesophilic production (37 °C). The optimal pH for H₂ production was 6.0 for both raw and ozonated POME. The POME concentrations were greatly influenced the yields and rates of H₂ production. At the optimal pH, the maximum H₂ production yield of 182 ± 7.2 mL.g⁻¹ COD (7.96 mmoL.g⁻¹ COD) was achieved at the ozonated POME concentration of 30,000 mg COD.L⁻¹. The maximum H₂ production rate (R_max) of 43.1 ± 2.5 mL.h⁻¹ was obtained at the ozonated POME concentration of 25,000 mg COD.L⁻¹. The highest total COD removal was 44% at of 15,000 mg COD.L⁻¹ ozonated POME. Acetic and butyric acids were dominant products during H₂ fermentation and tended to increase with the increased POME concentrations. Ozonation as a pretreatment process showed significant enhancement of the POME biodegradability , and subsequently improved the H₂ production H₂.     

Dark fermentative biohydrogen production by Acinetobacter junii-AH4 utilizing various industry wastewaters

Hydrogen (H₂) is one of the most promising renewable energy sources, anaerobic bacterial H₂ fermentation is considered as one of the most environmentally sustainable alternatives to meet the potential fossil fuel demand. Bio-H₂ is the cleanest and most effective source of energy provided by the dark fermentation utilizing organic substrates and different wastewaters. In this study, the bio-H₂ production was achieved by using the bacteria Acinetobacter junii-AH4. Further, optimization was carried out at different pH (5.0–8.0) in the presence of wastewaters as substrates (Rice mill wastewater (RMWW), Food wastewater (FWW) and Sugar wastewater (SWW). In this way, the optimized experiments excelled with the maximum cumulative H₂ production of 566.44 ± 3.5 mL/L (100% FWW at pH 7.5) in the presence of Acinetobacter junii-AH4. To achieve this, a bioreactor (3 L) was employed for the effective production of H₂ and Acinetobacter junii-AH4 has shown the highest cumulative H₂ of 613.2 ± 3.0 mL/L, HPR of 8.5 ± 0.4 mL/L/h, HY of 1.8 ± 0.09 mol H₂/mol glucose. Altogether, the present study showed a COD removal efficiency of 79.9 ± 3.5% by utilizing 100% food wastewater at pH 7.5. The modeled data established a batch fermentation system for sustainable H₂ production. This study has aided to achieve an ecofriendly approach using specific wastewaters for the production of bio-H₂.     

Effect of iron and molybdenum addition on photofermentative hydrogen production from olive mill wastewater

Photofermentative hydrogen production from olive mill wastewater (OMW) by Rhodobacter sphaeroides O.U.001 was assessed under iron and molybdenum supplementation. Control cultures were only grown with 2% OMW containing media. The analysis included measurements of biomass accumulation, hydrogen production, pH variations of the medium, and changes in the chemical oxygen demand (COD) of the wastewater. Growth under control and Mo-supplemented experiments yielded about the same amount of biomass (∼0.4 g dry cell weight per L culture). On the other hand, Mo addition slightly enhanced the total volume of H₂ gas production (62 mL H₂), in comparison with the control reactor (40 mL H₂). Fe-supplemented cultures showed a significant increase on H₂ production (125 mL H₂), tough having a longer lag time for the observation of the first H₂ bubbles (24 h), compared to the control (15 h) and Mo-supplemented ones (15 h). Fe-added cultures also yielded better wastewater treatment by achieving 48.1% degradation of the initial chemical oxygen demand (COD) value compared to the control reactor having 30.2% COD removal efficiency. Advances described in this work have the potential to find applications in hydrogen industry while attempting an effective management of cheap feedstock utilization.     

Improved hydrogen gas production in electrohydrolysis of vinegar fermentation wastewater by scrap aluminum and salt addition

Scrap aluminum particles and salt (NaCl) were added to the vinegar fermentation wastewater to improve hydrogen gas formation by electrohydrolysis of the wastewater organics. The applied DC voltage and initial COD of the wastewater were constant at 4 V and 33.16 g L⁻¹, respectively. The highest cumulative hydrogen gas formation (2877 mL) was obtained with scrap Al (1 g L⁻¹) and NaCl (1 g L⁻¹) additions within 72 h as compared to 1925 mL H₂ gas formation from raw wastewater. Hydrogen gas formation from Al and NaCl added water was 302 ml as compared to 260 ml from raw water. The highest H₂ gas formation rate (952 mL d⁻¹), the yield (1660 mL H₂ g⁻¹ COD) and the highest current intensity (163 mA) were also obtained with combined effects of scrap Al and NaCl additions. Almost pure hydrogen gas (99%) was produced using the raw wastewater. Initial conductivity of the raw wastewater increased from 1.80 mS cm⁻¹ to 5.01 mS cm⁻¹ with the addition of scrap Al and salt for which the final conductivities were 4.0 mS cm⁻¹ and 6.91 mS cm⁻¹, respectively. The highest energy conversion efficiency was obtained with only scrap Al addition (37.8%) as compared to 30.5% efficiency obtained with Al and salt additions. Additions of NaCl and scrap Al particles was found to be very beneficial for H₂ gas formation by electrohydrolysis of vinegar fermentation wastewater.     

Electro-hydrolysis of cheese whey solution for hydrogen gas production and chemical oxygen demand (COD) removal using photo-voltaic cells (PVC)

Diluted cheese whey (CW) solution was used for hydrogen gas production by electro-hydrolysis using photo-voltaic cells (PVC) as source of electricity. Effects of initial chemical oxygen demand (COD) concentration on the rate and yield of hydrogen gas production were investigated using a completely mixed and sealed reactor with aluminum electrodes. Cumulative hydrogen gas formation (CHF) increased with increasing initial COD concentration. The highest cumulative hydrogen gas volume (26472 mL), hydrogen gas production rate (4553 mL d⁻¹), hydrogen yield (7004 mL H₂ g⁻¹ COD), and percent COD removal (21.5%) were obtained with initial COD of 35172 mg L⁻¹. H₂ gas formation from water control was only 5365 mL. pH of the CW solution increased with decreasing conductivities during the course of experiments. Gas phase contained more than 99% H₂ at the end of experiments. The highest energy efficiency (20.4%) was also obtained with the highest COD content. Nearly pure hydrogen gas formation by electro-hydrolysis of cheese whey using PVC panels was proven to be an effective method.     

Effects of substrate concentration and hydraulic retention time on hydrogen production from common reed by enriched mixed culture in continuous anaerobic bioreactor

This study aims to investigate the effect of substrate concentration and hydraulic retention time (HRT) on hydrogen production in a continuous anaerobic bioreactor from unhydrolyzed common reed (Phragmites australis) an invasive wetland and perennial grass. The bioreactor has capacity of 1 L and working volume of 600 mL. It was operated at pH 5.5, temperature at 37 °C, hydraulic retention time (HRT) 12 h, and variation of substrate concentration from 40, 50, and 60 g COD/L, respectively. Afterward, the HRT was then varied from 12, 8, to 4 h for checking the optimal biohydrogen production. Each condition was run until reach steady state on hydrogen production rate (HPR) which based on hydrogen percentage and daily volume. The results were obtained the peak of substrate concentration was at the 50 g COD/L with HRT 12 h, average HPR and H₂ concentration were 28.71 mL/L/h and 36.29%, respectively. The hydrogen yield was achieved at 106.23 mL H₂/g CODre. The substrate concentration was controlled at 50 g COD/L for the optimal HRT experiments. It was found that the maximum of average HPR and H₂ concentration were 43.28 mL/L/h and 36.96%, respectively peak at HRT 8 h with the corresponding hydrogen yield of 144.35 mL H₂/g CODre. Finally, this study successful produce hydrogen from unhydrolyzed common reed by enriched mixed culture in continuous anaerobic bioreactor.     

Effect of system optimizing conditions on biohydrogen production from herbal wastewater by slaughterhouse sludge

The study evaluates the biohydrogen production from herbal wastewater as the substrate by the enriched mixed slaughterhouse sludge as the seed source. In the following experiments, batch-fermentations are carried out with the optimum substrate concentrations, fermentation pH and fermentation temperature to observe the effects of H₂ production, hydrogen yield and other fermentation end products at different conditions. The hydrogen production is increased as substrate concentration increased up to 8 g COD/L WW, but drastically decreased at 10 g COD/L WW. When the pH of fermentation is controlled to 6.5, a maximum amount of hydrogen yield could be obtained. The hydrogen production is maximum at 50 °C (930 ± 30 mL/L WW) compared to 30 °C (436 ± 16 mL/L WW). Acid-forming pathway with butyric acid as a major metabolite dominated the metabolic flow during the hydrogen production. The experimental results indicated that effective hydrogen production from the herbal wastewater could be obtained by thermophilic acidogenesis at proper operational conditions.