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Vinegar fermentation wastewater with an initial chemical oxygen demand (COD) content of was subjected to electrohydrolysis using aluminium, copper, and stainless-steel electrodes for hydrogen gas production. The applied DC voltage was constant at 4 V. The highest cumulative hydrogen production (2,098 ml), hydrogen yield (), hydrogen formation rate (), percent hydrogen (99.5%) in the gas phase, percent COD removal (12%), and energy efficiency (21.3%) was obtained with the aluminium electrode. Hydrogen gas production by water electrolysis was 260 ml with the Al electrode, and wastewater control resulted in nearly in 96 h. Hydrogen gas was produced by reaction of () ions released from acetic acid and electrons provided by DC current. Aluminium electrode was the most suitable one among the others tested. [ABSTRACT FROM AUTHOR]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Abstract: 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. [Copyright &y& Elsevier]

Cheese whey (CW) was subjected to DC voltages between 0.5 and 5 V for hydrogen gas production with simultaneous COD removal by electrohydrolysis of CW organics. Hydrogen gas formation and COD removal were investigated at different DC voltages using aluminum electrodes. The highest cumulative hydrogen production (5551 mL), hydrogen yield (1709 mL H 2 g −1 COD), hydrogen gas formation rate (913 ml d −1 ), and percent hydrogen (99%) in the gas phase were obtained with 5 V DC voltage within 158 h. Energy conversion efficiency reached the highest level (80.7%) at 3 V DC voltage with cumulative hydrogen production of 4808 mL and hydrogen yield of 1366 mL H 2 g −1 COD. Hydrogen gas was mainly produced by electrohydrolysis of CW organics due to low H 2 gas production in water and CW control experiments. The highest COD removal (22%) was also obtained with 3 V DC voltage. Major COD removal mechanism was anaerobic degradation of carbohydrates producing volatile fatty acids (VFA) and CO 2 . Hydrogen gas was produced by reaction of protons released from VFAs and electrons provided by DC current. Hydrogen gas production by electrohydrolysis of CW solution was proven to be an effective method with simultaneous COD removal. [ABSTRACT FROM AUTHOR]

Abstract: Cheese whey (CW) was subjected to DC voltages between 0.5 and 5 V for hydrogen gas production with simultaneous COD removal by electrohydrolysis of CW organics. Hydrogen gas formation and COD removal were investigated at different DC voltages using aluminum electrodes. The highest cumulative hydrogen production (5551 mL), hydrogen yield (1709 mL H2 g−1 COD), hydrogen gas formation rate (913 ml d−1), and percent hydrogen (99%) in the gas phase were obtained with 5 V DC voltage within 158 h. Energy conversion efficiency reached the highest level (80.7%) at 3 V DC voltage with cumulative hydrogen production of 4808 mL and hydrogen yield of 1366 mL H2 g−1 COD. Hydrogen gas was mainly produced by electrohydrolysis of CW organics due to low H2 gas production in water and CW control experiments. The highest COD removal (22%) was also obtained with 3 V DC voltage. Major COD removal mechanism was anaerobic degradation of carbohydrates producing volatile fatty acids (VFA) and CO2. Hydrogen gas was produced by reaction of protons released from VFAs and electrons provided by DC current. Hydrogen gas production by electrohydrolysis of CW solution was proven to be an effective method with simultaneous COD removal. [Copyright &y& Elsevier]

Abstract: Cheese whey powder (CWP) solution was used as the raw material for hydrogen gas production by mesophilic (35 °C) and thermophilic (55 °C) dark fermentations at constant initial total sugar and bacteria concentrations. Thermophilic fermentation yielded higher cumulative hydrogen formation (CHF = 171 mL), higher hydrogen yield (111 mL H2 g−1 total sugar), and higher hydrogen formation rate (3.46 mL H2 L−1 h−1) as compared to mesophilic fermentation. CHF in both cases were correlated with the Gompertz equation and the constants were determined. Despite the longer lag phase, thermophilic fermentation yielded higher specific H2 formation rate (2.10 mL H2 g−1cells h−1). Favorable results obtained in thermophilic fermentation were probably due to elimination of H2 consuming bacteria at high temperatures and selection of fast hydrogen gas producers. [Copyright &y& Elsevier]

Abstract: Hydrogen gas production from cheese whey powder (CWP) solution by thermophilic dark fermentation was investigated at 55 °C. Experiments were performed at different initial total sugar concentrations varying between 5.2 and 28.5 g L−1 with a constant initial bacteria concentration of 1 g L−1. The highest cumulative hydrogen evolution (257 mL) was obtained with 20 g L−1 total sugar (substrate) concentration within 360 h while the highest H2 formation rate (2.55 mL h−1) and yield (1.03 mol H2 mol−1 glucose) were obtained at 5.2 and 9.5 g L−1 substrate concentrations, respectively. The specific H2 production rate (SHPR = 4.5 mL h−1 g−1cells) reached the highest level at 20 g L−1 total sugar concentration. Total volatile fatty acid (TVFA) concentration increased with increasing initial total sugar content and reached the highest level (14.15 g L−1) at 28.5 g L−1 initial substrate concentration. The experimental data was correlated with the Gompertz equation and the constants were determined. The optimum initial total sugar concentration was 20 g L−1 above which substrate and product (VFA) inhibitions were observed. [Copyright &y& Elsevier]

Abstract: Waste ground wheat was subjected to acid hydrolysis (pH = 3.0) at 90 °C for 15 min using an autoclave. The sugar solution obtained from acid hydrolysis was subjected to dark fermentation for hydrogen gas production after neutralization. In the first set of experiments, initial total sugar concentration was varied between 3.9 and 27.5 g L−1 at constant biomass (cell) concentration of 1.3 g L−1. Biomass concentration was varied between 0.28 g L−1 and 1.38 g L−1 at initial total sugar concentration of 7.2 ± 0.2 g L−1 in the second set of experiments. The highest hydrogen yield (1.46 mol H2 mol−1 glucose) and the specific formation rate (83.6 ml H2 g−1 cell h−1) were obtained with 10 g L−1 initial total sugar concentration. Biomass (cell) concentration affected the specific hydrogen production rate yielding the highest rate (1221 ml H2 g−1 cell h−1) and the yield at the lowest (0.28 g L−1) initial biomass concentration. The most suitable Xo /So ratio, maximizing the yield and specific rate of hydrogen gas formation was Xo /So  = 0.037. Dark fermentation of acid hydrolyzed ground wheat was found to be more beneficial as compared to simultaneous bacterial hydrolysis and fermentation. [Copyright &y& Elsevier]

Abstract: Hydrogen gas production from acid hydrolyzed waste wheat starch by combined dark and photo-fermentation was investigated in continuous mode with periodic feeding and effluent removal. A mixture of heat treated anaerobic sludge and Rhodobacter sphaeroides (NRRL-B 1727) were used as the seed culture for dark and light fermentations, respectively with biomass ratio of Rhodobacter/sludge=3. Hydraulic residence time (HRT) was changed between 1 and 8 days by adjusting the feeding periods. Ground waste wheat was acid hydrolyzed at pH=3 and 121°C for 30min using an autoclave and the resulting sugar solution was used as the substrate for combined fermentation after pH adjustment and nutrient addition. The highest daily hydrogen gas production (41mld−1), hydrogen yield (470mlg−1 total sugar=3.4mol H2 mol−1glucose), volumetric and specific hydrogen production rates were obtained at the HRT of 8 days. The highest biomass and the lowest total volatile fatty acids (TVFA) concentrations were also realized at HRT=8 days indicating VFA fermentation by Rhodobacter sp. at high HRTs. The lowest total sugar loading rate of 0.625gL−1 d−1 resulted in the highest hydrogen yield and formation rate. Hydrogen gas production by combined fermentation with periodic feeding was proven to be an effective method resulting in high hydrogen yields at long HRTs. [Copyright &y& Elsevier]

Abstract: Hydrogen gas production with simultaneous COD removal was realized by application of DC voltages (0.5–5.0V) to landfill leachate. The rate and the yield of hydrogen gas production were investigated at different DC voltages by using aluminum electrodes and DC power supply. The highest cumulative hydrogen production (5000mL), hydrogen yield (2400mLH2 g−1 COD), daily hydrogen gas formation (1277mLd−1), and percent hydrogen (99%) in the gas phase were obtained with 4V DC voltage. Energy conversion efficiency (H2 energy/electrical energy) reached the highest level (80.6%) with 1V DC voltage. Hydrogen gas production was mainly realized by electrohydrolysis of leachate organics due to negligible H2 gas production in water and leachate control experiments. The highest COD removal (77%) was also obtained with 4V DC voltage. Electrohydrolysis of landfill leachate was proven to be an effective method for hydrogen gas production with simultaneous COD removal. [Copyright &y& Elsevier]

Abstract: This article overviews reported studies on bio-hydrogen production from different raw materials by dark and photo-fermentations operated with different modes. Sequential and combined dark and photo-fermentations operated in batch, continuous and fed-batch modes were compared. Operating conditions and modes resulting in the highest hydrogen yield and formation rate were revealed. Relative advantages of sequential and combined dark and photo-fermentations were discussed. Sequential fermentation was found to be preferable due to high H2 yields and productivities. High cell density fed-batch culture with controlled feeding and simultaneous product removal was concluded to be the most suitable operation mode at the optimum environmental conditions. [Copyright &y& Elsevier]

Abstract: Dark fermentation experiments were performed for bio-hydrogen production from ground wheat starch solution (10 ± 1 g l−1) using periodic feeding and effluent removal. A mixed culture of Clostridium butyricum-NRRL 1024 and Clostridium pasteurianum-NRRL B-598 were used with an initial biomass ratio of 1/1.Effects of wheat starch loading rate on the rate and yield of bio-hydrogen formation were investigated. Substrate loading rate was varied between 0.54 and 5.52 g d−1 (HRT = 6–60 h). The highest hydrogen formation rate (280 ml d−1), volumetric hydrogen formation rate (1857 ml H2 l−1 d−1) and volatile fatty acids (VFAs) concentration were obtained with a substrate loading rate of 5.52 g d−1 (HRT = 6 h). The highest hydrogen yield (109 ml H2 g TS −1) was obtained with a substrate loading rate of 1.38 g d−1. [Copyright &y& Elsevier]

The degradation and mineralization of amoxicillin in an aqueous solution was accomplished by using a photo-Fenton treatment. An ultraviolet light source with a 254-nm wavelength was used with hydrogen peroxide (H2O2) and iron(II). The effects of reagent concentrations on amoxicillin degradation and mineralization were investigated systematically by using the Box-Behnken statistical experiment design. Amoxicillin (10-200 mgL-1), H2O2 (10-500 mgL-1), and iron(II) (0-50 mgL-1) concentrations were considered independent variables; the percent amoxicillin degradation and the total organic carbon (TOC) removal (mineralization) were the objective functions to be maximized. Both H2O2 and iron(II) concentrations affected the extent of the amoxicillin degradation and mineralization. The amoxicillin degradation was completed within 2.5 min, and 53% mineralization took place within 60 min. The optimum H2O2∶Fe∶amoxicillin ratio that resulted in complete amoxicillin degradation and 53% mineralization was 100∶40∶105 mgL-1. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen gas production by photo-fermentation of dark fermentation effluent of acid hydrolyzed wheat starch was investigated at different hydraulic residence times (HRT = 1–10 days). Pure Rhodobacter sphaeroides (NRRL B-1727) culture was used in continuous photo-fermentation by periodic feeding and effluent removal. The highest daily hydrogen gas production (85 ml d−1) was obtained at HRT = 4 days (96 h) while the highest hydrogen yield (1200 ml H2 g−1 TVFA) was realized at HRT = 196 h. Specific and volumetric hydrogen formation rates were also the highest at HRT = 96 h. Steady-state biomass concentrations and biomass yields increased with increasing HRT. TVFA loading rates of 0.32 g L−1 d−1 and 0.51 g L−1 d−1 resulted in the highest hydrogen yield and formation rate, respectively. Hydrogen gas yield obtained in this study compares favorably with the relevant literature reports probably due to operation by periodic feeding and effluent removal. [Copyright &y& Elsevier]

Abstract: Diluted olive mill wastewater (OMW) was subjected to direct current (DC) voltages (0.5–4.0V) for hydrogen gas production with simultaneous chemical oxygen demand (COD) removal by electrohydrolysis. The highest cumulative hydrogen production (3020ml) and hydrogen yield (2500mlH2 g−1 COD) were obtained with 3V DC voltage while the highest current intensity (80mA), percent hydrogen (95%) in the gas phase, hydrogen gas formation rate (614mld−1), percent COD removal (44%) and energy conversion efficiency (95%) were realized with 2V. Hydrogen gas production by electrolysis of water was negligible for all voltages. COD removal from OMW with no DC voltage application was usually lower than that obtained with DC power application. Hydrogen gas production by electrohydrolysis of OMW was proven to be a fast and effective method with simultaneous COD removal. [Copyright &y& Elsevier]

Abstract: Electrical power generated by a photovoltaic cell (PVC) was supplied to diluted industrial wastewater in a mechanically mixed and sealed stainless-steel reactor for hydrogen gas production. Three different electrodes, graphite, stainless steel and aluminum rods were used for comparison. Protons released from decomposition of organic compounds and electrons provided by the DC current reacted to form hydrogen gas. The highest cumulative hydrogen gas formation (CHF) was obtained with the aluminum electrode (120 L in 8 days) and the lowest was with the graphite electrode (4 L). Hydrogen gas production from wastewater was 2.4 times higher than that produced from water when aluminum electrodes were used. TOC content of wastewater was reduced from 2400 to 1700 mg L−1 with nearly 29% TOC removal within 6 days. CHF from wastewater was 76 L within 18 days with the stainless-steel electrodes while CHF from water was only 9.5 L. Fermentative hydrogen gas production from wastewater was negligible in the absence PVC. Energy conversion efficiency for hydrogen gas production (hydrogen energy/electric energy) was found to be 74% with the aluminum electrodes. [Copyright &y& Elsevier]

Abstract: Batch dark fermentation experiments were performed to investigate the effects of biomass and substrate concentration on bio-hydrogen production from acid hydrolyzed ground wheat at 55 °C. In the first set of experiments, the substrate concentration was constant at 20 g total sugar L−1 and biomass concentration was varied between 0.52 and 2.58 g L−1. Total sugar concentration was varied between 4.2 and 23.7 g L−1 in the second set of experiments with a 1.5 g L−1 constant biomass concentration. The highest cumulative hydrogen formation (582 mL, 30 °C, 1 atm), formation rate (5.43 mL h−1) and final total volatile fatty acid (TVFA) concentration (6.54 g L−1) were obtained with 1.32 g L−1 biomass concentration. In variable substrate concentration experiments, the highest cumulative hydrogen (365 mL) and TVFA concentration (4.8 g L−1) were obtained with 19.25 g L−1 initial total sugar concentration while hydrogen gas formation rate (12.95 mL h−1) and the yield (200 mL H2 g−1 total sugar) were the highest with 4.2 g L−1 total sugar concentration. [Copyright &y& Elsevier]

Abstract: Waste anaerobic sludge was subjected to different DC voltages (0.5–5 V) for hydrogen gas production by using aluminum electrodes and a DC power supply. Effects of applied DC voltage on the rate and extent of hydrogen gas production were investigated. The highest cumulative hydrogen production (2775 ml), daily hydrogen gas formation (686.7 ml d−1), hydrogen yield (96 ml H2 g−1 COD) and percent hydrogen (94.3%) in the gas phase were obtained with 2 V DC voltage. Energy conversion efficiency (H2 energy/electrical energy) also reached the highest level (74%) with 2 V DC voltage application. Control experiments with no voltage application to the sludge yielded almost the same level of COD removal, but no hydrogen gas production. Voltage application to water resulted in much lower hydrogen gas production as compared to sludge indicating negligible electrolysis of water. The results indicated that the sludge was naturally decomposed by the active cells removing COD and releasing hydrogen ions to the medium which reacted with the electrons provided by DC current to produce hydrogen gas. Hydrogen gas production from electrohydrolysis of waste sludge was found to be a fast and effective method with high energy efficiency. [Copyright &y& Elsevier]

Abstract: Electrical current generated by a photovoltaic cell (PVC) was supplied to wastewater in a mechanically mixed and sealed reactor using stainless steel electrodes. Hydrogen gas was generated by reaction of protons released from decomposition of organic compounds and electrons provided by electrical current. Gas phase was composed of 75–99% H2 gas. Hydrogen gas produced from electrolysis of water (9.5 L) was only 12.5% of that produced from wastewater (75 L) within 432 h. TOC content of wastewater was reduced from 4800 to 4200 mg L−1 with nearly 12.5% TOC removal. Fermentative hydrogen gas production from wastewater was negligible in the absence PVC power. Wastewater inoculated with anaerobic sludge generated higher hydrogen gas volumes as compared to wastewater with the application of solar power. Energy conversion efficiency for hydrogen production by electrohydrolysis of waste compounds (hydrogen energy/electric energy) was found to be 92% for the wastewater containing anaerobic sludge. [ABSTRACT FROM AUTHOR]

Abstract: Para-chlorophenol (4-chlorophenol, 4-CP) containing synthetic wastewater was treated using a rotating perforated tubes biofilm reactor (RTBR). Box–Wilson statistical experiment design and response surface methodology (RSM) were used to investigate the effects of the feed COD, 4-CP contents and the A/Q (biofilm surface/flow rate) ratio on percent COD, 4-CP and toxicity removals. Increases in A/Q ratio and the feed COD contents improved COD, 4-CP and toxicity removals. High feed 4-CP contents adversely affected the system performance due to toxic effects of 4-CP on microorganisms. High A/Q ratio and feed COD contents were required for effective 4-CP and toxicity removals at high feed 4-CP contents. More than 95% 4-CP and toxicity removals were obtained with an A/Q ratio of 186m2 d m−3, and feed COD of 6000mg L−1 with the feed 4-CP content of 1000mg L−1. The RTBR was proven to be more efficient than the RBBR used for the same purpose in our previous studies. [ABSTRACT FROM AUTHOR]

Abstract: Pure culture of Rhodobacter sphaeroides (NRRL- B1727) was used for continuous photo-fermentation of volatile fatty acids (VFA) present in the dark fermentation effluent of ground wheat starch. The feed contained 1950±50mgL−1 total VFA with some nutrient supplementation. Hydraulic residence time (HRT) was varied between 24 and 120hours. The highest steady-state daily hydrogen production (55mld−1) and hydrogen yield (185ml H2 g−1 VFA) were obtained at HRT=72hours (3 days). Biomass concentration increased with increasing HRT. Volumetric and specific hydrogen formation rates were also maximum at HRT=72h. High extent of TVFA fermentation at HRT=72h resulted in high hydrogen gas production. [Copyright &y& Elsevier]

Abstract: Advanced oxidation of amoxicillin was realized in aqueous solution by using Fenton''s reagent treatment. Box–Behnken statistical experiment design was used to determine the effects of reagent concentrations on amoxicillin degradation and mineralization. Amoxicillin (10–200mgL−1), hydrogen peroxide (10–500mgL−1) and Fe(II) (0–50mgL−1) concentrations were considered as independent variables in batch oxidation experiments. Percent amoxicillin and total organic carbon (TOC) removals (mineralization) were considered as the objective functions to be maximized. Required reaction times were 2.5min and 15min, respectively for degradation and mineralization of amoxicillin. Both peroxide and amoxicillin concentrations affected the extent of amoxicillin degradation and mineralization. Complete amoxicillin degradation was obtained within 2.5min while 37% mineralization took place within 15min. The optimum peroxide/Fe/amoxicillin ratio resulting in complete amoxicillin degradation and 37% mineralization was 255/25/105mgL−1. [Copyright &y& Elsevier]

Abstract: Continuous combined fermentation of ground wheat starch was realized in an annular-hybrid bioreactor (AHB) for hydrogen gas production. A mixture of pure cultures of Clostridium beijerinkii (DSMZ-791) and Rhodobacter sphaeroides-RV were used as seed cultures in combined fermentation. The feed contained 5 g L−1 ground wheat with some nutrient supplementation. Effects of hydraulic residence time (HRT) on the rate and yield of hydrogen gas formation were investigated. Steady-state daily hydrogen production decreased but, hydrogen yield increased with increasing HRT. The highest hydrogen yield was 90 ml g−1 starch at HRT of 6 days. Hydrolysis of starch and fermentation of glucose to volatile fatty acids (VFA) were readily realized at all HRTs. However, slow conversion of VFAs to H2 and CO2 by photo-fermentation caused accumulation of VFAs in the medium. Specific and volumetric rates of hydrogen formation also decreased with increasing HRT. High hydrogen yields obtained at high HRTs are due to partial fermentation of VFAs by Rhodobacter sp. The system should be operated at HRTs longer than 5 days for effective hydrogen gas formation by the dark and photo-fermentation bacteria. [Copyright &y& Elsevier]

Abstract: Bio-hydrogen production by combined dark and light fermentation of ground wheat starch was investigated using fed-batch operation. Serum bottles containing heat-treated anaerobic sludge and a mixture of Rhodobacter sp. was fed with a medium containing 20gdm−3 wheat powder (WP) at a constant flow rate. The system was operated at different initial dark/light biomass ratios (D/L). The optimum D/L ratio was 1/2 yielding the highest cumulative hydrogen (1548cm3), yield (65.2cm3 g−1 starch), and specific hydrogen production rate (5.18cm3 g−1 h−1). Light fermentation alone yielded higher hydrogen production than dark fermentation due to fermentation of volatile fatty acids (VFAs) to H2 and CO2. The lowest hydrogen formation was obtained with D/L ratio of 1/1 due to accumulation of VFAs in the medium. [Copyright &y& Elsevier]

Composition of the mixed culture was varied in combined dark-light fermentation of wheat powder starch in order to improve hydrogen gas formation rate and yield. Heat-treated anaerobic sludge and pure culture of Clostridium beijerinckii ( DSMZ 791 T) were combined with two different light fermentation bacteria of Rhodobacter sphaeroides (RS-NRRL and RS-RV) in order to select a more suitable mixture resulting in high hydrogen yield and formation rate. A combination of the anaerobic sludge and RS-NRRL yielded the highest cumulative hydrogen (CHF = 140 ml), the highest yield (0.36 mol H2 mol−1 glucose) and specific hydrogen formation rate (2.5 ml H2 g−1 biomass h−1). During dark fermentation (70 h) hydrogen was produced simultaneously by the dark and light fermentation bacteria using glucose from hydrolyzed starch. However, only light fermentation bacteria produced hydrogen from VFA’s derived from dark fermentation after a long adaptation period. [ABSTRACT FROM AUTHOR]

Abstract: Dark fermentation effluent of wheat powder solution was subjected to light fermentation for bio-hydrogen production using different light sources and intensities. Tungsten, fluorescent, infrared (IR), halogen lamps were used as light sources with a light intensity of 270Wm−2 along with sunlight. Pure culture of Rhodobacter sphaeroides-RV was used in batch light fermentation experiments. Halogen lamp was found to be the most suitable light source yielding the highest cumulative hydrogen formation (CHF, 252ml) and yield (781ml H2 g−1 TVFA). In the second set of experiments, light fermentations were performed at different light intensities (1–10klux) using halogen lamp. The optimum light intensity was found to be 5klux (approx. 176Wm−2) resulting in the highest CHF (88ml) and hydrogen yield (1037ml H2 g−1TVFA). Hydrogen formation was limited by the availability of light at low light intensities below 5klux and was inhibited by the excess light above 5klux. [Copyright &y& Elsevier]

Abstract: Combined dark and photo-fermentation of ground wheat starch was carried out by using different light sources, intensities and lighting regime. A mixture of heat treated anaerobic sludge and Rhodobacter sphaeroides-RV with a certain light/dark bacteria ratio was used in batch experiments. Tungsten, fluorescent, infrared (IR), tungsten + infrared, halogen lamps were used as light sources with a light intensity of 270 Wm−2 along with sunlight. Halogen lamp was found to be the most suitable light source yielding the highest cumulative hydrogen formation (178 ml) and yield (218 ml g−1 starch). Combined fermentations were performed at different light intensities (1–10 klux) using the halogen lamp in the second set of experiments. The optimum light intensity was found to be 10 klux (approx. 352 Wm−2) resulting in the highest cumulative hydrogen (111 ml) and hydrogen yield (139 ml H2 g−1 starch). Hydrogen formation was limited by the availability of light at low light intensities below 10 klux. Durations of dark/light cycles were changed to determine the most suitable lighting regime. Hydrogen gas formation increased with increasing cycle time and continuous lighting resulted in the highest cumulative hydrogen formation and hydrogen yield. [Copyright &y& Elsevier]

Abstract: Ground wheat powder solution (10 g L−1) was subjected to combined dark and light fermentations for bio-hydrogen production by fed-batch operation. A mixture of heat treated anaerobic sludge (AN) and Rhodobacter sphaeroides-NRRL (RS-NRRL) were used as the mixed culture of dark and light fermentation bacteria with an initial dark/light biomass ratio of 1/2. Effects of wheat starch loading rate on the rate and yield of bio-hydrogen formation were investigated. The highest cumulative hydrogen formation (CHF = 3460 ml), hydrogen yield (201 ml H2 g−1 starch) and formation rate (18.1 ml h−1) were obtained with a starch loading rate of 80.4 mg S h−1. Complete starch hydrolysis and glucose fermentation were achieved within 96 h of fed-batch operation producing volatile fatty acids (VFA) and H2. Fermentation of VFAs by photo-fermentation for bio-hydrogen production was most effective at starch loading rate of 80.4 mg S h−1. Hydrogen formation by combined fermentation took place by a fast dark fermentation followed by a rather slow light fermentation after a lag period. [Copyright &y& Elsevier]

Advanced oxidation of simazine in aqueous solution by the peroxone (hydrogen peroxide/ozone) treatment was investigated using Box-Behnken statistical experiment design and response surface methodology. Effects of pH, simazine and H2O2 concentrations on percent simazine and total organic carbon (TOC) removals were investigated. Ozone concentration was kept constant at 45 mg L-1. The optimum conditions yielding the highest simazine and TOC removals were also determined. Both simazine and peroxide doses affected simazine removal while pH and pesticide dose had more pronounced effect on mineralization (TOC removal) of simazine. Nearly 95% removal of simazine was achieved within 5 min for simazine and peroxide concentrations of 2.0 and 75 mg L-1, respectively at pH=7. However, mineralization of simazine was not completed even after 60 min at simazine doses above 2 mg L-1 indicating formation of some intermediate compounds. The optimum H2O2/pH/Simazine ratio resulting in maximum pesticide (94%) and TOC removal (82%) was found to be 75/11/0.5(mg L-1). [ABSTRACT FROM AUTHOR]

Abstract: Three different pre-treatment methods were applied on two different anaerobic sludge cultures and their mixtures in order to investigate the effects of pre-treatment methods on bio-hydrogen production from dark fermentation of waste ground wheat solution. Repeated heat, chloroform and combinations of heat and chloroform pre-treatment methods were applied to anaerobic sludges from different sources. Repeated heat treatment (2×5h) was found to be more effective in selecting hydrogen producing bacteria compared to the other treatment methods tested on the basis of cumulative hydrogen production. The highest hydrogen formation (652ml) and specific hydrogen production rate (SHPR=25.7mlH2 g−1 cellsh−1) were obtained with the anaerobic sludge pre-treated by repeated boiling. Both the type of anaerobic sludge and the pre-treatment method had considerable effects on bio-hydrogen production from wheat powder solution (WPS) by dark fermentation. [Copyright &y& Elsevier]

Abstract: Removal of simazine from aqueous solution by Fenton''s reagent oxidation was investigated. Box–Behnken statistical experiment design and the response surface methods were used to investigate the effects of simazine, H2O2 and Fe (II) concentrations on simazine degradation and mineralization. Total organic carbon (TOC) and simazine removals were investigated at different reagent doses to determine the experimental conditions yielding the highest removal of simazine and TOC. Fe (II) concentration had more profound effect than H2O2 for simazine removal while all parameters affected mineralization (TOC removal). Complete disappearance of simazine was achieved within 6min reaction period. However, only 32% of simazine was mineralized after 15min indicating formation of some intermediate products. The optimal H2O2/Fe (II)/simazine ratio resulting in the maximum pesticide (100%) and TOC removal (32%) was found to be 55/15/3 (mgL−1). The initial rate of simazine degradation was found to be first-order with respect to the initial simazine concentration. [Copyright &y& Elsevier]

Abstract: Effects of the substrate and cell concentration on bio-hydrogen production from ground wheat solution were investigated in combined dark-light fermentations. The ratio of the dark to light bacteria concentration (D/L) was kept constant at 1/10 while the wheat powder (WP) concentration was changed between 2.5 and 20gL−1 with a total cell concentration of 0.41gL−1 in the first set of experiments. Cell concentration was changed between 0.5 and 5gL−1 in the second set of experiments while the wheat powder concentration was constant at 5gL−1 with a D/L ratio of 1/7. The highest cumulative hydrogen (135ml) and formation rate (3.44mlH2 h−1) were obtained with the 20gL−1 wheat powder concentration. However, the highest yield (63.9mlg−1 starch) was obtained with the 2.5gL−1 wheat powder. In variable cell concentration experiments, the highest cumulative hydrogen (118ml) and yield (156.8mlH2 g−1 starch) were obtained with 1.1gL−1 cell concentration yielding an optimal biomass/substrate ratio of 0.22gcells/gWP. [Copyright &y& Elsevier]

Removal of simazine from aqueous solution by photo-Fenton oxidation was investigated using Box-Behnken statistical experiment design and the response surface analysis. The effects of simazine, hydrogen peroxide (H202), and iron(II) concentrations on the extent of simazine and total organic carbon (TOC) removals were investigated. Optimum reagent doses yielding the highest simazine and TOC removals were determined. The iron(II) Concentration had a more pronounced effect than hydrogen peroxide on the percent simazine removal, while all parameters affected the mineralization (TOC removal) of simazine. Nearly complete removal of simazine was achieved within 6 minutes. However, complete mineralization of simazine was not achieved, even within 60 minutes at high simazine doses, indicating the formation of some intermediate products. The optimal H202/Fe(II)/simazine ratio, resulting in the maximum pesticide (100%) and TOC removal (100%), was found to be 50/30/0.5 (mg/L). Water Environ. Res., 81, 735 (2009). [ABSTRACT FROM AUTHOR]

Abstract: Ground waste wheat was subjected to combined dark and light batch fermentation for hydrogen production. The dark to light biomass ratio (D/L) was changed between 1/2 and 1/10 in order to determine the optimum D/L ratio yielding the highest hydrogen formation rate and the yield. Hydrogen production by only dark and light fermentation bacteria was also realized along with the combined fermentations. The highest cumulative hydrogen formation (CHF=76ml), hydrogen yield (176mlH2 g−1 starch) and formation rate (12.2mlH2 g−1 biomassh−1) were obtained with the D/L ratio of 1/7 while the lowest CHF was obtained with the D/L ratio of 1/2. Dark–light combined fermentation with D/L ratio of 1/7 was faster as compared to the dark and light fermentations alone yielding high hydrogen productivity and reduced fermentation time. Dark and light fermentations alone also yielded considerable cumulative hydrogen, but slower than the combined fermentation. [Copyright &y& Elsevier]

Removal of diuron from aqueous solution by peroxone (hydrogen peroxide/ozone) oxidation was investigated using Box-Behnken statistical experiment design and the response surface methodology (RSM). Effects of diuron, H2O2 concentrations and initial pH on the extent of diuron, total organic carbon (TOC) and adsorbable organic halogen (AOX) removals were investigated. Ozone dose was kept constant at 45 mg min-1. Optimum reagent doses yielding the highest diuron, TOC and AOX removals were also determined. Hydrogen peroxide dose and pH were the most effective parameters for pesticide removal while hydrogen peroxide dose had the most significant effect on AOX removal (dehalogenation). All parameters affected mineralization (TOC removal) of diuron. Nearly complete removal of diuron was achieved within 5 minutes, while complete mineralization and dehalogenation were not achieved even within 60 minutes at high diuron doses indicating formation of some intermediate products. The optimal H2O2/pH/diuron ratio resulting in the maximum pesticide (100%), TOC (82%) and AOX (95%) removal was found to be 340/8/10. [ABSTRACT FROM AUTHOR]

Biological treatment of synthetic wastewater containing Cu(II) ions was realized in an activated sludge unit with pre-adsorption of Cu(II) onto powdered waste sludge (PWS). Box-Behnken experimental design method was used to investigate Cu(II), chemical oxygen demand (COD) and toxicity removal performance of the activated sludge unit under different operating conditions. The independent variables were the solids retention time (SRT, 5–30d), hydraulic residence time (HRT, 5–25h), feed Cu(II) concentration (0–50mgL−1) and PWS loading rate (0–4gh−1) while percent Cu(II), COD, toxicity (TOX) removals and the sludge volume index (SVI) were the objective functions. The data were correlated with a quadratic response function (R 2 =0.99). Cu(II), COD and toxicity removals increased with increasing PWS loading rate and SRT while decreasing with the increasing feed Cu(II) concentration and HRT. Optimum conditions resulting in maximum Cu(II), COD, toxicity removals and SVI values were found to be SRT of 30d, HRT 15h, PWS loading rate 3gh−1 and feed Cu(II) concentration of less than 30mgL−1. [Copyright &y& Elsevier]

Abstract: Ground wheat solution was used for bio-hydrogen production by dark fermentation using heat-treated anaerobic sludge in a completely mixed fermenter operating in fed-batch mode. The feed wheat powder (WP) solution was fed to the anaerobic fermenter with a constant flow rate of 8.33mLh−1 (200mLd−1). Cumulative hydrogen production, starch utilization and hydrogen yields were determined at three different WP loading rates corresponding to the feed WP concentrations of 10, 20 and 30gL−1. The residual starch (substrate) concentration in the fermenter decreased with operation time while starch consumption was increasing. The highest cumulative hydrogen production (3600mL), hydrogen yield (465mL H2 g−1 starch or 3.1mol H2 mol−1 glucose) and hydrogen production rate (864mL H2 d−1) were obtained after 4 days of fed-batch operation with the 20gL−1 feed WP concentration corresponding to a WP loading rate of 4g WPd−1. Low feed WP concentrations (10gL−1) resulted in low hydrogen yields and rates due to substrate limitations. High feed WP concentrations (30gL−1) resulted in the formation of volatile fatty acids (VFAs) in high concentrations causing inhibition on the rate and yield of hydrogen production. [Copyright &y& Elsevier]

Abstract: Hydrogen gas production from sugar solution derived from acid hydrolysis of ground wheat starch by photo-fermentation was investigated. Three different pure strains of Rhodobacter sphaeroides (RV, NRLL and DSZM) were used in batch experiments to select the most suitable strain. The ground wheat was hydrolyzed in acid solution at pH=3 and 90°C in an autoclave for 15min. The resulting sugar solution was used for hydrogen production by photo-fermentation after neutralization and nutrient addition. R. sphaeroides RV resulted in the highest cumulative hydrogen gas formation (178ml), hydrogen yield (1.23molH2 mol−1 glucose) and specific hydrogen production rate (46mlH2 g−1 biomassh−1) at 5gl−1 initial total sugar concentration among the other pure cultures. Effects of initial sugar concentration on photo-fermentation performance were investigated by varying sugar concentration between 2.2 and 13gl−1 using the pure culture of R. sphaeroides RV. Cumulative hydrogen volume increased from 30 to 232ml when total sugar concentration was increased from 2.2 to 8.5gl−1. Further increases in initial sugar concentration resulted in decreases in cumulative hydrogen formation. The highest hydrogen formation rate (3.69mlh−1) and yield (1.23molH2 mol−1 glucose) were obtained at a sugar concentration of 5gl−1. [Copyright &y& Elsevier]

Abstract: Hydrogen formation performances of different anaerobic bacteria were investigated in batch dark fermentation of waste wheat powder solution (WPS). Serum bottles containing wheat powder were inoculated with pure cultures of Clostridium acetobutylicum (CAB), Clostridium butyricum (CB), Enterobacter aerogenes (EA), heat-treated anaerobic sludge (ANS) and a mixture of those cultures (MIX). Cumulative hydrogen formation (CHF), hydrogen yield (HY) and specific hydrogen production rate (SHPR) were determined for every culture. The heat-treated anaerobic sludge was found to be the most effective culture with a cumulative hydrogen formation of 560 ml, hydrogen yield of 223 ml H2 g−1 starch and a specific hydrogen production rate of 32.1 ml H2 g−1 h−1. [Copyright &y& Elsevier]

Synthetic wastewater containing 2,4-dichlorophenol (DCP) was biologically treated using a hybrid-loop bioreactor system consisting of a packed column biofilm reactor (PCBR) and an aerated tank with effluent recycle. Effects of the feed DCP concentration on COD, DCP and toxicity removals were investigated. Biomass concentration in the packed column and in the aeration tank decreased with increasing feed DCP content due to toxic effects of DCP on the microorganisms. Low biomass concentrations at high DCP contents resulted in low COD, DCP and toxicity removals. Therefore, percent DCP, COD and toxicity removals decreased with increasing feed DCP content. Nearly 70% COD removal was achieved with a feed DCP content of 380mgL−1. The system should be operated with the feed DCP lower than 100mgL−1 in order to obtain DCP, COD and toxicity removals above 90%. [Copyright &y& Elsevier]

Abstract: Due to the toxic effects of trichlorophenol (TCP) on microorganisms, biological treatment efficiencies of TCP containing wastewaters are usually low. Synthetic wastewater containing 2,4,6-TCP was biologically treated in a hybrid-loop bioreactor system consisting of a packed column biofilm and an aerated tank bioreactor with effluent recycle in order to improve COD and TCP removals. Effects of the feed TCP concentration on COD, TCP and toxicity removal performance of the system were investigated for the feed TCP between 50 and 450mgL−1 while the sludge age (solids retention time, SRT) and hydraulic residence time (HRT) were kept constant at 20d and 25h, respectively. Biomass concentrations in the packed column and in the aeration tank decreased with increasing feed TCP concentrations due to toxic effects of TCP on the organisms. Low biomass concentrations in the system at high feed TCP contents resulted in low COD, TCP and toxicity removals. Therefore, percent TCP, COD and toxicity removals decreased with increasing feed TCP concentrations especially above 400mgL−1. The effluent TCP concentrations were lower than 20mgL−1 for the feed TCP concentrations below 390mgL−1 resulting in TCP and COD removals above 90%. Specific rates of TCP and COD removals increased with the feed TCP due to low biomass concentrations at high TCP contents. The system should be operated at a feed TCP lower than 400mgL−1 in order to obtain more than 90% TCP, COD and toxicity removals under the specified experimental conditions. [Copyright &y& Elsevier]

Abstract: Dark fermentation effluents of wheat powder (WP) solution containing different concentrations of volatile fatty acids (VFAs) were subjected to low voltage (1–3V) DC current to produce hydrogen gas. Graphite and copper electrodes were tested and the copper electrode was found to be more effective due to higher electrical conductivity. The effects of solution pH (2–7), applied voltage (1–3V) and the total VFA (TVFA) concentration (1–5gL−1) on hydrogen gas production were investigated. Hydrogen production increased with decreasing pH and became maximum at pH=2. Increases in applied voltage and the TVFA concentration also increased the cumulative hydrogen formation. The most suitable conditions for the highest cumulative hydrogen production was pH=2, with 3V applied voltage and 5g TVFA L−1. Up to 110ml hydrogen gas was obtained with 5gL−1 TVFA at pH=5.8 and 2V applied voltage within 37.5h. The highest energy efficiency (56%) was obtained with the 2V applied voltage and 10.85gL−1 TVFA. Hydrogen production by electrolysis of water in control experiments was negligible for pH>4. Hydrogen production by electrohydrolysis of VFA containing anaerobic treatment effluents was found to be an effective method with high energy efficiency. [Copyright &y& Elsevier]

Abstract: Three different Rhodobacter sphaeroides (RS) strains (RS–NRRL, RS–DSMZ and RS–RV) and their combinations were used for light fermentation of dark fermentation effluent of ground wheat containing volatile fatty acids (VFA). In terms of cumulative hydrogen formation, RS–NRRL performed better than the other two strains producing 48mlH2 in 180h. However, RS–RV resulted in the highest hydrogen yield of 250mlH2 g−1 TVFA. Specific hydrogen production rate (SHPR) with the RS–NRRL was also better in comparison to the others (13.8mlH2 g−1 biomassh−1). When combinations of those three strains were used, RS–RV+RS–DSMZ resulted in the highest cumulative hydrogen formation (90mlH2 in 330h). However, hydrogen yield (693mlH2 g−1 TVFA) and SHPR (12.1mlH2 g−1 biomassh−1) were higher with the combination of the three different strains. On the basis of Gompertz equation coefficients mixed culture of the three different strains gave the highest cumulative hydrogen and formation rate probably due to synergistic interaction among the strains. The effects of initial TVFA and NH4–N concentrations on hydrogen formation were investigated for the mixed culture of the three strains. The optimum TVFA and NH4–N concentrations maximizing the hydrogen formation were determined as 2350 and 47mgL−1, respectively. [Copyright &y& Elsevier]

Advanced oxidation of diuron in aqueous solution by photo-Fenton treatment was investigated by batch experiments. Effects of operating parameters, namely, the concentrations of pesticide (diuron), hydrogen peroxide (H2O2), and ferrous ion [Fe (II)] on oxidation of diuron were investigated by using Box-Behnken statistical experiment design and the response surface methodology. Diuron oxidation by photo-Fenton treatment was evaluated by determining the total organic carbon (TOC), diuron, and adsorbable organic halogen (AOX) removals. Concentration ranges of the reagents resulting in the highest level of diuron oxidation were determined. Diuron removal increased with increasing H2O2 and Fe (II) concentrations, up to a certain level. H2O2 concentration had a more profound effect than diuron and Fe (II) on removal of diuron, TOC, and AOX from the aqueous solution. Complete (100%) disappearance of diuron was achieved after a 15 min reaction period. However, 85% of diuron was mineralized after 240 min, indicating a low level of intermediate formation. Optimal H2O2/Fe (II)/diuron ratio resulting in maximum diuron (100%), TOC (85%), and AOX (100%) removals was found to be 267/36/25 (mg L-1). [ABSTRACT FROM AUTHOR]

Abstract: Synthetic wastewater containing different concentrations of 2,4,6-trichlorophenol (TCP) was biologically treated using a novel rotating perforated-tubes biofilm reactor (RTBR) for chemical oxygen demand (COD), TCP and toxicity removal. Performance of the reactor was investigated as function of major operating variables such as the feed TCP and COD concentrations and A/Q (biofilm surface area/feed flow rate) ratio. A Box–Behnken statistical experiment design method was used by considering the feed TCP (0–400mgL−1), COD (1000–4000mgL−1) and A/Q ratio (23–163m2 dm−3) as the independent variables while percent TCP, COD, and toxicity removals were the objective functions. The results were correlated with the quadratic model since this was found to be the most suitable one. Response function coefficients were determined by correlating the experimental data with the response function. Percent TCP, COD and toxicity removals estimated from the response functions were in good agreement with the experimental results. TCP, COD and toxicity removals increased with increasing A/Q ratio and decreasing feed TCP concentrations. Percent toxicity removals were always lower than TCP removals indicating presence or formation of some toxic by products from TCP biodegradation. For the feed TCP of 400mgL−1, the optimum conditions resulting in maximum COD (99%), TCP (100%) and toxicity (93%) removals were A/Q ratio of nearly 165m2 dm−3 and feed COD of 2985mgL−1. [Copyright &y& Elsevier]

Abstract: Powdered wheat solution was fermented batchwise for bio-hydrogen production using heat-treated anaerobic-acidogenic sludge as the inoculum at initial pH of 7.0 and temperature of 37°C. In order to determine the most suitable wheat powder (WP) and cell concentrations yielding the highest hydrogen formation, initial WP concentration was varied between 5 and 30gL−1 at a constant initial biomass concentration (2.6gL−1). The initial biomass concentration was varied between 0.5 and 5.0gL−1 at constant WP concentration of 20gL−1 in another set of experiments. Cumulative bio-hydrogen formation, hydrogen yield and the formation rate were maximum at the WP concentration of 20gL−1. Higher WP concentrations resulted in lower fermentation performance probably due to substrate and product (VFA) inhibition. Similarly, hydrogen formation rate and the yield were maximum with a biomass concentration of 2.5gL−1. Higher biomass concentrations resulted in lower hydrogen yield and formation rates due to product inhibition. The optimum initial biomass/substrate ratio maximizing the hydrogen yield and formation rate was found to be 0.125g biomassg−1 WP. A kinetic model was developed for bio-hydrogen formation from powdered wheat starch and the constants were determined by regression analysis. [Copyright &y& Elsevier]

Abstract: Cheese whey powder (CWP) solution containing 50gL−1 total sugar was fermented to ethanol in a continuously operated packed column bioreactor (PCBR) using olive pits as support particles for cell attachment. Pure culture of Kluyveromyces marxianus (DSMZ 7239) was used in the PCBR for ethanol formation from lactose content of CWP solution. Sugar utilization and ethanol formation were investigated as function of the hydraulic residence time (HRT) between 17.6 and 64.4h. Sugar concentration decreased with increasing ethanol concentration along the height of the column. Percent sugar utilization increased while effluent sugar concentration was decreasing with HRT between 17.6 and 50h. Similarly, effluent ethanol concentration increased while ethanol productivity was decreasing with increasing HRT up to 50h. Further increases in HRT above 50h resulted in decreases in effluent ethanol concentration. The ethanol yield coefficient also increased with increasing HRT and reached the highest level of 0.54gEg−1S at an HRT of 50h. Due to cell settling to the bottom of the column, high fermentation rates were obtained in the lower section of the system. Therefore, the system can be operated with a height of 36cm from the inlet to obtain high ethanol contents in the effluent with an HRT of 18h. [Copyright &y& Elsevier]

Synthetic wastewater containing Cu(II) in concentrations between 0 and 22 mg L −1 was treated in an activated sludge unit, and chemical oxygen demand (COD), Cu(II), and toxicity removals were investigated. The feed Cu(II)o concentrations were varied between 0 and 22 mg L −1 while the feed CODo, hydraulic residence time (HRT) and solids retention time (SRT) were kept constant at 2,000 ± 100 mg L −1, 10 h and 10 days, respectively. The effluent CODe and Cu(II)e concentrations, toxicity, and the sludge volume index (SVI) increased, but the biomass concentration in the aeration tank decreased with the feed Cu(II)o content due to Cu(II) toxicity on the organisms. The feed and the effluent toxicities were determined by using the resazurin assay based on dehydrogenase activity. Cu(II) toxicity in the feed and the effluent wastewater increased linearly with the Cu(II) concentrations. Adverse effects of Cu(II) were more pronounced for the feed Cu(II)o above 10 mg L −1, resulting in sharp decreases in biomass concentration and percent COD removal. A kinetic model describing the Cu(II) inhibition on COD removal rate was developed and the Cu(II) inhibition constant was found to be 2.85 mg L−1. [ABSTRACT FROM AUTHOR]

Abstract: Kinetics of biodegradation of 2,4,6-trichlorophenol (TCP) by pure culture of Rhodococcus rhodochrous (DSM 43241) was investigated in batch culture. Batch experiments were performed with different initial TCP concentrations between 50 and 400mgL−1 at pH 7 and 30°C in the presence of basal salts medium containing glucose. Percent TCP and toxicity removals decreased with increasing initial TCP concentration due to toxic effects of TCP. The rate and the extent of TCP degradation increased with TCP concentration up to150mgL−1 indicating no TCP inhibition at low TCP concentrations. TCP concentrations above 150mgL−1 resulted in decreases both in the rate and extent of TCP degradation due to toxic effects of high TCP contents. The kinetics of TCP biodegradation was modeled by relating the initial TCP degradation rates with the initial TCP concentrations using the non-competitive inhibition model. The kinetic constants were determined by using the experimental data. Percent toxicity removal was also quantified along with TCP removal which decreased with increasing initial TCP concentrations due to toxic effects of TCP. [Copyright &y& Elsevier]