Assessing potential cathodes for resource recovery through wastewater treatment and salinity removal using non-buffered microbial electrochemical systems.

The present study evaluates relative functioning of microbial electrochemical systems (MES) for simultaneous wastewater treatment, desalination and resource recovery. Two MES were designed having abiotic cathode (MES-A) and algal biocathode (MES-B) which were investigated with synthetic feed and saline water as proxy of typical real-field wastewater. Comparative anodic and cathodic efficiencies revealed a distinct disparity in both the MES when operated in open circuit (OC) and closed circuit (CC). The maximum open circuit voltage (OCV) read in MES-A and MES-B was about 700mV and 600mV, respectively. Salinity and organic carbon removal efficiencies were noticed high during CC operation as 72% and 55% in MES-A and 60% and 63% in MES-B. These discrete observations evidenced ascribe to the influence of microbial electrochemical induced ion-migration over cathodic reduction reactions (CRR).

Generation of bioethanol and VFA through anaerobic acidogenic fermentation route with press mud obtained from sugar mill as a feedstock.

Acidogenic anaerobic fermentation route was explored for the production of bioethanol and volatile fatty acids (VFA) from the press mud (PM) obtained from sugar mill. Slurry was prepared from PM having 10% of total solids and the same was hydrolyzed under acidic thermal conditions. Both press mud slurry (PMS) and pre-treated press mud slurry (PTPMS) was used as feedstock with mixed microbial consortia (MMC) and enriched mixed microbial consortia (EMMC). Mix of bioethanol and VFA were obtained in all the four cases (PMS-MMC, PMS-EMMC, PTPMS-EMC and PTPMS-EMMC), but, bioethanol and VFA yield of 0.04 g/g and 0.27 g/g, respectively obtained from PTPMS with EMMC was found to be comparatively higher. Control experiments carried out with glucose yielded bioethanol and VFA of 0.042 g/g and 0.28 g/g, respectively demonstrating that the organism was using reducible sugars in the feedstock for the generation of bioethanol by simultaneously producing the VFA from COD.

Applied potentials regulate recovery of residual hydrogen from acid-rich effluents: Influence of biocathodic buffer capacity over process performance.

An absolute biological microbial electrolysis cell (MEC) was operated for a prolonged period under different applied potentials (Eapp, -0.2V to -1.0V) and hydrogen (H2) production was observed using acid-rich effluent. Among these potentials, an optimal voltage of -0.6 V influenced the biocathode by which maximum H2 production of 120 ± 9 ml was noticed. This finding was corroborated with dehydrogenase activity (1.8 ± 0.1 µg/ml) which is the key enzyme for H2 production. The in situ biocathode regulated buffer overpotentials which was remarkably observed by the change in peak heights of dissociation value (pKa) from the titration curve. Substrate degradation analysis gave an estimate of coulombic efficiency of about 72 ± 5% when operated at optimal voltage. Evidently, the electron transfer from solid carbon electrode to biocathode was analyzed by cyclic voltammetry and its derivatives showed the involvement of redox mediators. Despite, the MEC endures certain activation overpotentials which were estimated from the Tafel slope analysis.

Integrating sequencing batch reactor with bio-electrochemical treatment for augmenting remediation efficiency of complex petrochemical wastewater.

The present study evaluates the sequential integration of two advanced biological treatment methods viz., sequencing batch reactor (SBR) and bioelectrochemical treatment systems (BET) for the treatment of real-field petrochemical wastewater (PCW). Initially two SBR reactors were operated in aerobic (SBR(Ae)) and anoxic (SBR(Ax)) microenvironments with an organic loading rate (OLR) of 9.68 kg COD/m(3)-day. Relatively, SBR(Ax) showed higher substrate degradation (3.34 kg COD/m(3)-day) compared to SBR(Ae) (2.9 kg COD/m(3)-day). To further improve treatment efficiency, the effluents from SBR process were fed to BET reactors. BET(Ax) depicted higher SDR (1.92 kg COD/m(3)-day) with simultaneous power generation (17.12 mW/m(2)) followed by BET(Ae) (1.80 kg COD/m(3)-day; 14.25 mW/m(2)). Integrating both the processes documented significant improvement in COD removal efficiency due to the flexibility of combining multiple microenvironments sequentially. Results were supported with GC-MS and FTIR, which confirmed the increment in biodegradability of wastewater.

Acidogenic fermentation of food waste for volatile fatty acid production with co-generation of biohydrogen.

Fermentation experiments were designed to elucidate the functional role of the redox microenvironment on volatile fatty acid (VFA, short chain carboxylic acid) production and co-generation of biohydrogen (H2). Higher VFA productivity was observed at pH 10 operation (6.3g/l) followed by pH 9, pH 6, pH 5, pH 7, pH 8 and pH 11 (3.5 g/l). High degree of acidification, good system buffering capacity along with co-generation of higher H2 production from food waste was also noticed at alkaline condition. Experiments illustrated the role of initial pH on carboxylic acids synthesis. Alkaline redox conditions assist solubilization of carbohydrates, protein and fats and also suppress the growth of methanogens. Among the carboxylic acids, acetate fraction was higher at alkaline condition than corresponding neutral or acidic operations. Integrated process of VFA production from waste with co-generation of H2 can be considered as a green and sustainable platform for value-addition.

Temperature induced stress influence on biodiesel productivity during mixotrophic microalgae cultivation with wastewater.

The role of operating temperature as a physical stress factor for enhancing lipid induction during microalgae cultivation with domestic wastewater was evaluated. Experiments were designed with dual mode microalgae cultivation viz., growth phase (GP) and temperature induced stress phase (25 °C, 30 °C and 35 °C). GP showed enhancement in biomass growth and carbohydrate accumulation while stress phase (SP) operation at 30 °C showed noticeable improvement in lipid productivities (total/neutral lipid, 24.5/10.2%). Maximum carbohydrate utilization was observed during SP at 30 °C operation (57.8%) compared to 25 °C (50.6%) and 35 °C (26.9%) correlating well with the lipid synthesis. Interestingly the neutral lipid content documented five-fold increment illustrating feasibility towards good biodiesel properties. Biodiesel profile at 30 °C temperature is well supported by higher saturated fatty acids (SFA) to unsaturated fatty acids (USFA) ratio. GP operation showed good COD and nutrient removal concomitant to the biomass growth.

Regulatory function of organic carbon supplementation on biodiesel production during growth and nutrient stress phases of mixotrophic microalgae cultivation.

Critical role of organic carbon supplementation on the lipid synthesis during growth and nutrient deprived stress phase was investigated in present study. Mixotrophic cultivation showed relatively higher biomass productivity at lower carbon loading condition (500mgCOD/l). Nutrient deprivation induced physiological stress and glucose supplementation with 2000mgCOD/l supported higher lipid accumulation (26%). Glucose supplementation in mixotrophic growth phase showed distinct influence on biomass growth whereas glucose supplementation in nutrient starvation resulted in higher lipid storage. Compositional variation in FAME profile was observed with respect to saturated fatty acids when operated with increasing glucose concentrations. Mixotrophic mode of cultivation showed remarkable benefits of nutrient removal and organic carbon supplementation influenced greatly on biodiesel production which can be easily scaled up to pilot plant and large scale production facilities.

Systematic approach to assess biohydrogen potential of anaerobic sludge and soil rhizobia as biocatalysts: Influence of crucial factors affecting acidogenic fermentation.

A systematic protocol was designed to enumerate the variation in biohydrogen production with two different biocatalysts (sludge and soil) under different pH and organic loads. Both the biocatalysts showed cumulatively higher H2 production under acidogenic condition (pH 6) than at neutral pH condition. The cumulative hydrogen production was non-linearly fitted with modified Gompertz model and statistically validated. Pretreated soil biocatalyst showed relatively higher H2 production (OLR II, 142±5ml) than pretreated sludge (OLR I, 123±5ml); which was evidenced by substrate linked dehydrogenase activity and bio-electrochemical analysis. Experimental results revealed agricultural soil as a better biocatalyst than anaerobic sludge for all the operated process conditions. The voltammogram profiles and Tafel slopes revealed dominance of reductive catalytic activity of the pretreated inoculums substantiating dark-fermentation. Soil consortia showed low polarization resistance (2.24kΩ) and high reductive electron transfer efficiency (1.17 Vdec(-1)) at a high organic load; thus, rebating high H2 production.

Decentralized application of anaerobic digesters in small poultry farms: performance analysis of high rate self mixed anaerobic digester and conventional fixed dome anaerobic digester.

Biomethanation of poultry litter was studied in conventional fixed dome anaerobic digester (CFDAD) and high rate self mixed anaerobic digester (SMAD) for possible decentralized application in poultry farms generating litter in the range of 500 kg/day. The performance of CFDAD and SMAD was compared. The study revealed that optimized hydraulic residence time (HRT), volatile solids (VS) loading rate, VS reduction, methane yield was 24 days, 4.0 kg VS/m(3)/day, 64%, 0.15 m(3)/(kg VS fed) and 40 days, 2.15 kg/m(3)/day, 42%, 0.083 m(3)/(kg VS fed) for SMAD and CFDAD, respectively. Better results with SMAD could be attributed to specific design features and intermittent mixing of the digester contents due to self-mixing mechanism. Preliminary cost estimates revealed that installation of SMAD would be remunerative for the farmer in terms of biogas and bio-manure.

Nutritional mode influences lipid accumulation in microalgae with the function of carbon sequestration and nutrient supplementation.

Effect of nutritional mode viz., photoautotrophic, photoheterotrophic and photomixotrophic on the biomass growth and lipid productivity of microalgae was studied. Experiments were designed and operated in biphasic mode i.e., growth phase (GP) followed by stress induced starvation phase (SP). Nutritional mode documented marked influence on biomass growth and subsequent lipid productivity. Mixotrophic mode of operation showed higher biomass growth (4.45 mg/ml) during growth phase while higher lipid productivity was observed with nitrogen deprived autotrophic mode (28.2%) followed by heterotrophic (26.1%) and mixotrophic (19.6%) operations. Relative increments in lipid productivities were noticed in SP operation from GP in mixotrophic operation (2.45) followed by autotrophic (2.2) and heterotrophic (2.14) mode of operations. Higher concentrations of chlorophyll b and presence of lipid accumulating species supported the lipid biosynthesis. Algal fatty acid composition varied with function of nutritional modes and depicted eighteen types of saturated (SFA) and unsaturated fatty acids (USFA) with wide fuel and food characteristics.

Gas phase bio-filter for the removal of triethylamine (TEA) from air: microbial diversity analysis with reference to design parameters.

Biotic (packed bio-filter; PBF) and abiotic (packed filter; PF) studies were carried out on two similar 2L gas phase filters for the removal of triethylamine (TEA) at inlet concentration in the range of 250-280 ppmV. Removal efficiency (RE) of PBF remained in the range of 90-99% during the stable period of operation (170 days) whereas RE of PF dropped gradually to 10% in a span of 90 days. Five different bacterial species viz; Aeromonas sp., Alcaligenes sp., Arthrobacter sp., Klebsiella sp., and Pseudomonas sp., were identified in PBF. It was observed that diethyl amine, ethylamine and nitrate were formed as metabolites during the degradation pathway. Empty bed residence time of 20s, mass loading rate of 202.26 g/m(3)/h, space velocity of 178.82 m(3)/m(3)/h and elimination capacity of 201.52 g/m(3)/h were found to be optimum design parameters for PBF to get RE in the range of 90-99%.

Pseudomonas otitidis as a potential biocatalyst for polyhydroxyalkanoates (PHA) synthesis using synthetic wastewater and acidogenic effluents.

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.

Mass transfer dynamics of ammonia in high rate biomethanation of poultry litter leachate.

In the present study possibility of coupling biofilter to arrest ammonia (NH(3)) emission to the atmosphere from the integrated UASB and stripper (UASB+ST) system treating poultry litter leachate was studied. UASB+ST with biofilter (UASB+ST+BF) exhibited removal efficiency (RE) of NH(3) in the range of 98-99% (below 28 ppmV (parts per million by volume)) with low cost agricultural residue as a bedding material. Mass transfer dynamics of TAN in the system revealed that TAN loss to atmosphere was below 1% in UASB+ST+BF where as it was in the range of 70-90% in UASB+ST. Cost estimates revealed that financial implications due to the addition of biofilter were below 10% of total capital cost. TAN retained in the bedding material of biofilter could also be utilized as soil conditioner upon saturation.

An overview of sample preparation and extraction of synthetic pyrethroids from water, sediment and soil.

The latest developments in sample preparation and extraction of synthetic pyrethroids from environmental matrices viz., water, sediment and soil were reviewed. Though the synthetic pyrethroids were launched in 1970s, to the best of authors' knowledge there was no review on this subject until date. The present status and recent advances made during the last 10 years in sample preparation including conservation and extraction techniques used in determination of synthetic pyrethroids in water, sediment and soil were discussed. Pre- and post-extraction treatments, sample stability during extraction and its influence upon the whole process of analytical determination were covered. Relative merits and demerits including the green aspects of extraction were evaluated. The current trends and future prospects were also addressed.

Physiological acclimatization to heat after a spell of cold conditioning in tropical subjects.

The effects of brief spells of cold conditioning on heat acclimatized tropical subjects on the decay and reacclimatization status to heat were evaluated on 12 Indian male infantry soldiers in the cooler months at Delhi. After 8 d of heat acclimatization in a climatic chamber maintained at 45 degrees C dry bulb (Tdb) and 30% relative humidity (rh), the subjects were conditioned to cold for 21 d by exposing them to a temperature of 10 degrees C daily for 4 h. During the cold conditioning phase the subjects had no access to either heat exposure or strenuous work. The cold conditioning was followed by reacclimatization to heat. Significant loss in heat acclimatization status was observed, both in terms of exercise oral temperature and heart rate. The loss in status after 1 d reinduction to heat acclimatization was in the range of 45-56%. However, within 3 d all of the subjects once again regained the full acclimatization status. The cold conditioning did not alter the sweat output during the reinduction to heat phase.

Physiological responses during work in hot humid environments.

Studies have been conducted on 6 young healthy Indians in simulated comfortable, hot humid and very hot humid conditions to evaluate the physiological reactions during work. Physiological responses like exercise oxygen consumption (VO2), pulmonary ventilation (VE) and heart rate (HR) were noted during sub-maximal fixed work rates of 400, 500 and 600 kgM/min. In addition, duration of continuous work at these three rates of work, in the three simulated environments was also noted. Physiological responses i.e. VO2, VE and HR were noted every 15 minutes of work. Besides these responses, rectal temperature (Tr), mean skin temperature (Ts) and mean sweat rate were also noted during the continuous work. Results indicated a significantly higher oxygen cost (VO2) during 400 kgM/min of work in hot and very hot humid environments whereas, in the higher rates of work, the changes were not significant. The cardiac frequency showed a significantly higher rise during different grades of activities in hot and very hot environments except in the highest work rate in hotter environments, possibly due to attainment of maximum heart rate. The duration of continuous physical efforts in various grades of activities decreased significantly (P less than 0.001) in hot humid environments than in the comfortable temperature. During the progression of the work, the mean skin temperature decreased in comfortable temperature but increased in hot humid environments. The mean rectal temperature, increased during work in hot humid environment, and the rate of rise was much faster in higher work rates attaining the target temperature much earlier. The rate of sweating increased significantly as the heat load of the body increased. In hot humid environments, work performance decreased due to early attainment of maximum heart rate, reduction in VO2 max, disproportionate rise in rectal temperature, narrowing of the difference between the core and the skin temperature and attainment of maximum sweating rate.