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Abstract: Feasibility of integrating Microbial electrolysis cell (MEC) process with dark-fermentation process for additional hydrogen recovery as well as substrate degradation was demonstrated in the present study. MEC was employed in order to utilize the residual organic fraction present in the acidogenic effluents of dark fermentation process as substrate for hydrogen production with input of small electric current. MEC was operated at volatile fatty acids (VFA) concentration of 3000mg/l under different poised potentials (0.2, 0.5, 0.6, 0.8 and 1.0V) using anaerobic consortia as biocatalyst. Maximum hydrogen production rate (HPR), cumulative hydrogen production (CHP) (0.53mmol/h and 3.6mmol), dehydrogenase activity (1.65μg/ml) and VFA utilization (49.8%) was recorded at 0.6V. Bio-electrochemical behavior of mixed consortia was evaluated using cyclic voltammetry and by Tafel slope analysis. Microbial diversity analysis using denaturing gradient gel electrophoresis confirmed the presence of γ-proteobacteria (50%), Bacilli (25%) and Clostridia (25%). [Copyright &y& Elsevier]

Abstract: Influence of reactor configuration [biofilm/suspended growth] on fermentative hydrogen (H2) production and substrate degradation was evaluated employing anaerobic mixed consortia. Reactors were operated at acidophilic (pH 6.0) condition employing designed synthetic wastewater as substrate at an organic loading rate of 3.4Kg COD/m3-day with a retention time of 24h at 28±2 °C. Experimental data enumerated the influence of reactor configuration on both H2 production and wastewater treatment. Biofilm reactor (28.98mmol H2/day; 1.25Kg COD/m3-day) showed relatively efficient performance over the corresponding suspended growth configuration (20.93mmol H2/day; 1.08Kg COD/m3-day). Specific H2 yields of 6.96mmol H2/g-CODL-day (19.32mmol H2/g-CODR-day) and 5.03mmol H2/g-CODL-day (16.10mmol H2/g-CODR-day) were observed during stabilized phase of operation of biofilm and suspended growth reactors respectively. Higher concentration of VFA generation was observed in the biofilm reactor. Both the configurations recorded higher acetate concentration over other soluble metabolites indicating the dominance of acid-forming metabolic pathway during the H2 production process. [Copyright &y& Elsevier]

Abstract: Feasibility of integrating acidogenic and methanogenic processes for simultaneous production of biohydrogen (H2) and methane (CH4) was studied in two separate biofilm reactors from wastewater treatment. Acidogenic bioreactor (acidogenic sequencing batch biofilm reactor, AcSBBR) was operated with designed synthetic wastewater [organic loading rate (OLR) 4.75kg COD/m3-day] under acidophilic conditions (pH 6.0) using selectively enriched acidogenic mixed consortia. The resultant outlet from AcSBBR composed of fermentative soluble intermediates (with residual carbon source), was used as feed for subsequent methanogenic bioreactor (methanogenic/anaerobic sequencing batch biofilm reactor, AnSBBR, pH 7.0) to generate additional biogas (CH4) utilizing residual organic composition employing anaerobic mixed consortia. During the stabilized phase of operation (after 60 days) AcSBBR showed H2 production of 16.91mmol/day in association with COD removal efficiency of 36.56% (SDRA—1.736kgCOD/m3-day). AnSBBR showed additional COD removal efficiency of 54.44% (SDRM—1.071kgCOD/m3-day) along with CH4 generation. Integration of the acidogenic and methanogenic processes enhanced substrate degradation efficiency (SDRT—4.01kgCOD/m3-day) along with generation of both H2 and CH4 indicating sustainability of the process. [Copyright &y& Elsevier]

Abstract: Influence of different pretreatment methods applied on anaerobic mixed inoculum was evaluated for selectively enriching the hydrogen (H2) producing mixed culture using dairy wastewater as substrate. The experimental data showed the feasibility of molecular biohydrogen generation utilizing dairy wastewater as primary carbon source through metabolic participation. However, the efficiency of H2 evolution and substrate removal efficiency were found to be dependent on the type of pretreatment procedure adopted on the parent inoculum. Among the studied pretreatment methods, chemical pretreatment (2-bromoethane sulphonic acid sodium salt (0.2g/l); 24h) procedure enabled higher H2 yield along with concurrent substrate removal efficiency. On the contrary, heat-shock pretreatment (100°C; 1h) procedure resulted in relatively low H2 yield. Compared to control experiments all the adopted pretreatment methods documented higher H2 generation efficiency. In the case of combination experiments, integration of pH (pH 3; adjusted with ortho-phosphoric acid; 24h) and chemical pretreatment evidenced higher H2 production. Data envelopment analysis (DEA), a frontier analysis technique model was successfully applied to enumerate the relative efficiency of different pretreatment methods studied by considered pretreatment procedures as input and cumulative H2 production rate and substrate degradation rate as corresponding two outputs. [Copyright &y& Elsevier]

Abstract: Dairy wastewater was evaluated for biological hydrogen (H2) production in conjugation with wastewater treatment in a suspended growth sequencing batch reactor (AnSBR) employing sequentially pretreated [heat-shock (100°C, 2h) and acid (pH 3.0, 24h)] mixed consortia. The bioreactor was operated at mesophilic (room) temperature (28±2°C) under acidophilic conditions (pH 6.0) with a total cycle period of 24h consisting of FILL (15min), REACT (23h), SETTLE (30min), and DECANT (15min) phases at three different organic loading rates (OLR) of 2.4, 3.5, and 4.7KgCOD/m3-day, respectively. H2 evolution rate differed significantly with the substrate/OLR of wastewater used as substrate [OLR 2.4KgCOD/m3-day - volumetric H2 production rate: 0.3683mmol H2/m3-min; specific H2 production rate: 0.0184mmol H2/min-gCODL; OLR 3.5KgCOD/m3-day - volumetric H2 production rate: 1.105mmol H2/m3-min; specific H2 production rate: 0.0245mmol H2/min-gCODL and OLR 4.7KgCOD/m3-day - volumetric H2 production rate: 0.7367mmol H2/m3-min; specific H2 production rate: 0.0107mmol H2/min-gCODL]. Substrate (COD) removal efficiency of 64.7 (substrate degradation rate (SDR): 1.577KgCOD/m3-day), 60 (SDR: 3.168KgCOD/m3-day), and 50% (SDR-3.2KgCOD/m3-day), respectively, was observed at operating OLR of 2.4, 3.5, and 4.7KgCOD/m3-day, respectively. The system showed rapid stabilization tendency (2.4KgCOD/m3-day: 39 days; 3.5KgCOD/m3-day: 14 days; 4.7KgCOD/m3-day: 24 days) with respect to H2 generation and COD reduction. A surge in pH values from 5.8 to 4.5 (2.4KgCOD/m3-day), 5.82 to 4.62 (3.5KgCOD/m3-day), and 6.28 to 4.56 (4.7KgCOD/m3-day) was observed during stabilized phase of operation. [Copyright &y& Elsevier]

Molecular hydrogen (H2) production with simultaneous wastewater treatment was studied in biofilm configured periodic discontinuous/sequencing batch reactor using chemical wastewater as substrate. Anaerobic mixed consortia was sequentially pretreated with repeated heat-shock (100°C; 2h) and acid (pH—3.0; 24h) treatment procedures to selectively enrich the H2 producing mixed consortia prior to inoculation of the reactor. The bioreactor was operated at mesophilic (room) temperature (28±2°C) under acidophilic conditions with a total cycle period of 24h consisting of FILL (15min), REACT (23h), SETTLE (30min) and DECANT (15min) phases. Reactor was initially operated with synthetic wastewater (SW) at OLR of 4.8kgCOD/m3-day and subsequently operated using composite chemical wastewater (CW) at OLR of 5.6kgCOD/m3-day by adjusting pH to 6.0 prior to feeding to inhibit the methanogenic activity. H2 evolution rate differed significantly with the nature of wastewater used as substrate [SW—volumetric H2 production rate—12.89mmolH2/m3-min and specific H2 production rate—0.0084mmolH2/min-gCODL (0.026mmolH2/min-gCODR); CW—volumetric H2 production rate—6.076mmolH2/m3-min and specific H2 production rate—0.0089mmolH2/min-gCODL (0.033mmolH2/min-gCODR)]. Relatively rapid progress towards higher H2 yield (2h) was observed with SW compared to the CW (10h). Substrate (COD) reduction of 32.4% (substrate degradation rate (SDR)—1.55kgCOD/m3-day) and 26.7% (SDR-1.49kgCOD/m3-day) was observed with SW and CW, respectively. The system showed rapid stabilization tendency (SW—37 days; CW—40 days) with respect to H2 generation and COD reduction. H2 evolution showed relatively good correlation with VFA concentration in the case of SW (R 2-0.961) compared to CW (R 2-0.912). A surge in pH values from 5.87 to 4.23 (SW) and 5.93 to 4.62 (CW) was observed during the cycle operation. Integration of biofilm configuration with periodic discontinuous batch operation under the defined operating conditions showed potential to influence the microbial system by selectively enriching the specific group of microflora capable of producing H2. [Copyright &y& Elsevier]

Abstract: Synthesis of bioplastics (polyhydroxyalkanoates (PHA)) using Bacillus tequilensis, a newly isolated strain was investigated under aerobic condition using designed wastewater with synthetic acids (SA) and acidogenic fermented food waste (AFW) collected from biohydrogen (H2) producing anaerobic bioreactors as substrates. The isolate showed the ability to grow and accumulate PHA in both the substrates, with simultaneous waste remediation. Higher PHA synthesis was observed with SA (59% dry cell weight) compared to AFW (36% dry cell weight) with good substrate removal (SA, 87%; AFW, 59%). The PHA composition showed presence of co-polymer [P(3HB-co-3HV)] with varying contents of hydroxy butyrate (HB, 80–90%) and hydroxy valerate (HV, 10–15%) in both the substrates. High dehydrogenase activity was observed which leads to the formation of considerable quantity of PHA. AFW from H2 producing reactor as substrate contributes in reducing the production cost of both H2 as well as PHA embedded with waste valorization. [Copyright &y& Elsevier]

Abstract: Polyhydroxyalkanoates (PHA) production using Pseudomonas otitidis, a newly isolated strain from PHA producing bioreactor was investigated using synthetic acids (SA) and acidogenic effluents (AE) from biohydrogen reactor at different organic loading rates (OLRs). P. otitidis showed ability to grow and accumulate PHA, with simultaneous waste remediation. AE showed less PHA production (54%, OLR3), than SA (58%, OLR2). PHA composition showed co-polymer, poly-3(hydroxy butyrate-co-hydroxy valerate), P3(HB-co-HV). Bioprocess evaluation and enzymatic activities showed good correlation with PHA production. Kinetic studies on the growth of bacteria using different models at varying OLR were substantiated with PHA production. High substrate removal was registered at OLR1 (SA, 87%; AE, 82%). AE could be used as an alternative for pure substrates keeping in view of their high cost. [Copyright &y& Elsevier]

Abstract: An ecologically engineered system (EES) was designed to mimic the natural cleansing functions of wetlands to bring about wastewater treatment. EES consisted of three tanks containing diverse biota viz., aquatic macrophytes, submerged plants, emergent plants and filter feeders connected in series. The designed system was evaluated for 216days by operating in continuous mode (20l/day) to treat both sewage (DS) and fermented-distillery wastewater (FDW, from hydrogen producing bioreactor). Floating macrophyte system (Tank 1) was more effective in removing COD and nitrates. Submerged and emergent integrated macrophyte system (Tank 2) showed an effective removal of volatile fatty acids (VFAs) along with COD. Filter-feeding system (Tank 3) visualized the removal of COD, VFA, turbidity and color. On the whole the system can treat effectively DS (COD, 68.06%; nitrate, 22.41%; turbidity, 59.81%) and FDW (COD, 72.92%; nitrate, 23.15%; color, 46.0%). The designed EES can be considered as an economical approach for the treatment of both sewage and fermented wastewaters. [Copyright &y& Elsevier]

Abstract: The combined process efficiency with respect to fermentative hydrogen (H2) production and wastewater treatment was evaluated in a series of batch experiments to enumerate the role of selected factors viz., origin of inoculum, pre-treatment, inlet pH and feed composition under anaerobic microenvironment using mixed culture. H2 production and substrate degradation were found to depend significantly on the selected factors with individual conditions to achieve effective process performance. Significantly diverse operational conditions were observed for both H2 production and substrate degradation with respect to process efficiency. However, while dealing with H2 production in association with wastewater treatment, both the parameters are important and balancing the conditions for combined effective performance is critical. Data enveloping analysis (DEA) was applied to evaluate the combined system performance with respect to the two output parameters (H2 production and substrate degradation) based on relative efficiency. Among various experimental combinations studied, those with untreated anaerobic mixed inoculum under acidophilic conditions (inlet pH 5.5) using simple wastewater as fermentative substrate illustrated combined process efficiency with respect to H2 production (1.919mmolH2/day; 0.52molH2/kg CODR-day) and substrate degradation (substrate degradation rate, 4.56kg COD/m3-day). DEA methodology provide the relative efficiency of the system by integrating two output parameters. Further, design of experimental methodology (DOE) by Taguchi approach was applied to enumerate the role of selected factors on the H2 production and substrate degradation with the final aim of optimizing the process. By adapting the derived optimum conditions, the performance with respect to H2 production and substrate degradation could be enhanced by three fold. [Copyright &y& Elsevier]

Abstract: The influence of self-immobilization of enriched acidogenic mixed consortia on fermentative hydrogen (H2) production was studied on different supporting materials [SBA-15 (mesoporous) and activated carbon (granular; GAC and powder; PAC)] using chemical wastewater as substrate. Batch fermentation experiments were performed with same substrate at different organic loading rates (OLRs) under acidophilic microenvironment (pH 5.5) and room temperature (28±2°C). Experimental data evidenced the effectiveness of attached growth on both the H2 yields and substrate degradation efficiency, particularly at higher loading rates. Among the three materials evaluated, immobilization on SBA-15 material showed comparatively effective performance in enhancing both H2 yield and substrate degradation. Suspended growth (SG-control) culture showed inhibition in terms of both H2 production and substrate degradation especially at applied higher loading rates. Immobilization on SBA-15 resulted in nine times higher H2 production (7.29mol/kgCODR-day at OLR of 0.83kgCOD/m3-day) than the lowest yield observed (suspended growth at OLR of 2.55kg COD/m3-day). Maximum substrate degradation rate (SDR) of 0.96kgCOD/m3-day (OLR 2.55kgCOD/m3-day) was also observed with SBA-15 immobilization, which is 1.62 times higher than the lowest substrate degradation observed with SG-control experiments with the same OLR. Attached growth on GAC and PAC also showed remarkable improvement in the process performance at higher OLRs compared to SG-control. [Copyright &y& Elsevier]

Abstract: Bioelectricity generation from composite chemical wastewater treatment was evaluated in a dual chambered microbial fuel cell (MFC) [anode chamber (mediatorless; perforated plain graphite electrode); cathode chamber (50mM potassium ferricyanide [K3Fe(CN)6] in phosphate buffer; pH 7.5; plain graphite electrode)] inoculated with selectively enriched hydrogen (H2) producing mixed culture under acidophilic microenvironment (pH 5.5). Anode chamber, which resembles anaerobic suspended contact reactor was fed with wastewater and operated in absence of artificial mediator at acidic environment to proliferate H2 producing bacteria. Experimental data showed the feasibility of producing bioelectricity from wastewater treatment, though power production was found to be dependent on the substrate loading rate. Maximum voltage of 271.5mV (5.43mA) and 304mV (6.08mA) was recorded at operating organic loading rates (OLR) of 1.165kgCOD/(m3 day) and 1.404kgCOD/(m3 day), respectively when measured at 50Ω external resistors at stable operating conditions. COD removal efficiency of 35.4% (substrate degradation rate (SDR) of 0.412kgCOD/(m3 day)) and 62.9% (SDR, 0.88kgCOD/(m3 day)) was observed at OLRs 1.165kgCOD/(m3 day) and 1.404kgCOD/(m3 day), respectively. Maximum specific power production of 0.163W/kgCODR (1.165kgCOD/(m3 day); 50Ω) and 0.198W/kgCODR (1.404kgCOD/(m3 day); 100Ω) was observed during stable phase of fuel cell operation. Current density of 747.96mA/m2 (1.165kgCOD/(m3 day)) and 862.85mA/m2 (1.404kgCOD/(m3 day)) was documented at 10Ω. Utilizing chemical wastewater for the production of renewable energy (bioelectricity) from anaerobic treatment is considered as a feasible, economical and sustainable process. [Copyright &y& Elsevier]

Abstract: Photo-biological hydrogen production along with substrate degradation was evaluated by employing adopted photosynthetic mixed culture in batch experiments, in concurrence, with different types of wastewaters, organic loading rates (OLR), operating pH, presence of vitamins and sterilized/un-sterilized conditions. The experimental data indicates the feasibility of production along with substrate degradation. However, the efficacy of both production and substrate degradation was found to be dependent on the operating pH, organic loading rate OLR of the feed, nature of the substrate, presence of vitamins and sterilized/un-sterilized conditions. Maximum specific production was observed with designed synthetic wastewater (19.29mol/kg ; un-sterilized with vitamins; 3g glucose) followed by chemical wastewater (18.67mol/kg ; un-sterilized with vitamins) while maximum substrate degradation was observed with designed synthetic wastewater (; un-sterilized with/without vitamins; 6g glucose) followed by diary wastewater 2 [ (un-sterilized with vitamins); (sterilized); (un-sterilized); (sterilized with vitamins)]. The performance of the experimental variation studied was evaluated by employing frontier analysis technique (data enveloping analysis; DEA) considering relative efficiency, using production and substrate degradation as output parameters and OLR as input. DEA analysis evidenced that the best performance with respect to production and substrate degradation can be achieved with diary wastewater 2, chemical wastewater and designed synthetic wastewater. Among 20 experimental variation studies, about 70% of the designed experiments are found to be above 80% of the relative efficiency. DEA analysis also showed that the requirement of vitamins and need for sterilization were not crucial factors for achieving the best performance in terms of both the outputs studied. [Copyright &y& Elsevier]

Abstract: Biohydrogen (H2) production with simultaneous wastewater treatment was studied in anaerobic sequencing batch biofilm reactor (AnSBBR) using distillery wastewater as substrate at two operating pH values. Selectively enriched anaerobic mixed consortia sequentially pretreated with repeated heat-shock (100°C; 2h) and acid (pH ; 24h) methods, was used as parent inoculum to startup the bioreactor. The reactor was operated at ambient temperature () with detention time of 24h 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—26mmolH2/day; specific H2 production—6.98molH2/kgCODR-day) over neutral microenvironment (H2 production rate—7mmolH2/day; specific H2 production—1.63molH2/kgCODR-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. [Copyright &y& Elsevier]

Abstract: The basic aim of this study was to investigate the feasibility of bioaugmentation strategy in the process of enhancing biohydrogen (H2) production from chemical wastewater treatment (organic loading rate (OLR)—6.3kgCOD/m3-day) in anaerobic sequencing batch biofilm reactor (AnSBBR) operated at room temperature ( °C) under acidophilic microenvironment (pH 6) with a total cycle period of 24h. Parent augmented inoculum (kanamycin resistant) was acquired from an operating upflow anaerobic sludge blanket (UASB) reactor treating chemical wastewater and subjected to selective enrichment by applying repetitive/cyclic pre-treatment methods [altering between heat-shock treatment (100°C; 2h) and acid treatment (pH 3; 24h)] to eliminate non-spore forming bacteria and to inhibit the growth of methanogenic bacteria (MB). Experimental data revealed the positive influence of bioaugmentation strategy on the overall H2 production. Specific H2 production almost doubled after augmentation from 0.297 to 0.483mol H2/kg CODR-day. Chemical wastewater acted as primary carbon source in the metabolic reactions involving molecular H2 generation leading to substrate degradation. The augmented culture persisted in the system till the termination of the experiments. The survival and retention of the augmented inoculum and its positive effect on process enhancement may be attributed to the adopted reactor configuration and operating conditions. Scanning electron microscope (SEM) images documented the selective enrichment of morphologically similar group of bacteria capable of producing H2 under acidophilic conditions in anaerobic microenvironment. This depicted work corroborated successful application of bioaugmentation strategy to improve H2 production rate from anaerobic chemical wastewater treatment. [Copyright &y& Elsevier]