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In the present study, ozone assisted autohydrolysis (OAAH) was evaluated for enhanced generation of xylooligosaccharide (XOS) from wheat bran. The total XOS yield with optimum ozone dose of 3% (OAAH-3) was found to be 8.9% (w/w biomass) at 110 °C in comparison to 7.96% at 170 °C by autohydrolysis (AH) alone. Although, there was no significant difference in oligomeric composition (DP 2–6), significant decrease in degradation products namely furfural (2.78-fold), HMF (3.15-fold), acrylamide (nil) and acetic acid (1.06-fold), was observed with OAAH-3 as a pretreatment option. There was 1-fold higher xylan to XOS conversion and OAAH-hydrolysate had higher DPPH radical scavenging activity than AH. PCA plots indicated clear enhancement in XOS production and lower generation of inhibitors with decrease in treatment temperature. Results of the study therefore suggest OAAH can be an effective pretreatment option that can further be integrated with downstream processing for concentration and purification of XOS.

In this study, the concentrations of MgSO4, salinity and light intensity were optimised for maximum biomass productivity and lipid content in Chlorella sp. Lipid synthesized at varied experimental conditions was also assessed in detail for biodiesel properties through FAME analysis. FAMEs mainly composed of C16:0, C16:1(9), C16:3(7, 10, 13), C18:0, C18:1(11), C18:2(9, 12), C18:3(9, 12, 15). The optimum biomass productivity (372.50mgL(-1)d(-1)) and lipid content (32.57%) was obtained at MgSO4-150ppm; salinity-12.5ppm, and light intensity-25μmolm(-2)s(-1). However, at this condition the cetane number, a major biodiesel property was not complying with worldwide biodiesel standard. Therefore, further optimisations were done to check the suitability of biodiesel fuel. The optimum biomass productivity (348.47mgL(-1)d(-1)) and lipid content (12.43%) with suitable biodiesel fuel properties was obtained at MgSO4-50ppm, salinity-25ppm and light intensity-100μmolm(-2)s(-1). The validation experiments confirmed the closeness of predicted and measured response values.

Thermal assisted alkaline pretreatment (TAAP) of rice husk (RH) was investigated to facilitate enzymatic saccharification by enhancing the enzyme accessibility to cellulosic components. Statistically guided experiments based on the Box-Behnken design involving four factors viz. biomass loading, particle size, NaOH loading and reaction time was considered for optimization. The maximum sugar yield of 371 mg g−1 biomass was obtained at optimized pretreatment condition [biomass loading (10% w/w), particle size (0.25–0.625 mm), NaOH loading (2% w/w), and reaction time (40 min)]. The TAAP of RH resulted in the efficient removal of lignin (14.9–54% (w/w)) with low hemicellulose solubilization [10.7–33.1% (w/w)] and with a simultaneous increase in cellulose concentration [32.65–51.65% (w/w)]. The SEM analysis indicated increased porosity and biomass disruption during TAAP. The FTIR analysis showed progressive removal of noncellulosic constituents, and XRD analysis revealed an increase in cellulose crystallinity post-TAAP indicating the effectiveness of pretreatment.

This study looks at the possibility of wet air oxidation (WAO) based pretreatment of complex effluent to selectively enhance the biodegradability (without substantial COD destruction) and facilitate biogas generation potential. A lab-scale wet air oxidation reactor with biomethanated distillery wastewater (B-DWW) as a model complex effluent (COD 40,000 mg L −1 ) was used to demonstrate the proof-of-concept. The studies were conducted using a designed set of experiments and reaction temperature (150–200 °C), air pressure (6–12 bar) and reaction time (15–120 min) were the main process variables of concern for WAO process optimization. WAO pretreatment of B-DWW enhanced the biodegradability of the complex wastewater by the virtue of enhancing its biodegradability index (BI) from 0.2 to 0.88, which indicate favorable Biochemical Methane Potential (BMP) for biogas generation. The kinetics of COD destruction and BI enhancement has also been reported.

Scenedesmus obtusus, a freshwater microalga, was evaluated for its growth and biochemical characteristics under various culture conditions. S. obtusus was tolerant at all tested CO2 concentrations up to 20%. Among the different nitrogen sources, urea showed enhanced biomass productivities up to 2-fold compared to control, where the nitrogen source was sodium nitrate. Light intensity and photoperiod had a significant effect on growth rate and biomass productivity. The growth rate was observed maximum under continuous light exposure at the light intensities, 30μmolm(-2)sec(-1) and 60μmolm(-2)sec(-1) The species was able to tolerate the salinity levels up to 25mM NaCl, where, the increase in the concentration of NaCl suppressed the growth. Ammonium acetate and glycine showed better growth rate and biomass productivity indicating mixotrophic ability of S. obtusus. Supplementation of acetate and bicarbonate significantly enhanced the biomass productivity. Biodiesel properties of S. obtusus cultivated at various culture conditions were estimated.

The paper outlines treatment of waste gas containing monochlorobenzene (MCB) and benzene in a mixture using biofilter packed with compost and woodchips seeded with Acinetobacter calcoaceticus. The biofilter could treat waste gas containing MCB and benzene effectively with an efficiency of (99 ± 5%) and (97 ± 6%) at optimal empty bed contact time (EBCT) of 3 min with a loading of 57 g/m3/h of MCB and 2 g/m3/h of benzene. At optimum loading of MCB and benzene, the biofilter showed total bacterial count of 13 × 105 CFU/g of compost, while the MCB and benzene degrading bacterial count was 71 × 104 CFU/g and 5 × 104 CFU/g compost respectively. The experimental removal efficiency of MCB and benzene were in good agreement with the model predicted value.

Heterocyclic nitrogenous bases are one of the most important class of compounds containing N as a heteroatom, like pyridine and its derivatives. These compounds are of immense concern from point view of environment since they are known for their toxic and carcinogenic properties, lethal effect on natural biogenic environment and severe odour potential. There is a need to control these compounds from getting discharged into the environment. This paper addresses the different natural/anthropogenic sources which generate these pollutants, their toxicity profile, different physico-chemical treatment methods and especially focuses on biological methods of treatment and combination of these for the efficient removal to achieve a treated effluent quality fit for disposal without causing any damage to the environment.

Anaerobic dechlorination of technical grade hexachlorocyclohexane (THCH) was studied in a continuous upflow anaerobic sludge blanket (UASB) reactor with methanol as a supplementary substrate and electron donor. A reactor without methanol served as the experimental control. The inlet feed concentration of THCH in both the experimental and the control UASB reactor was 100 mg l(-1). After 60 days of continuous operation, the removal of THCH was99% in the methanol-supplemented reactor as compared to 20-35% in the control reactor. THCH was completely dechlorinated in the methanol fed reactor at 48 h HRT after 2 months of continuous operation. This period was also accompanied by increase in biomass in the reactor, which was not observed in the experimental control. Batch studies using other supplementary substrates as well as electron donors namely acetate, butyrate, formate and ethanol showed lower % dechlorination (85%) and dechlorination rates (3 mg g(-1)d(-1)) as compared to methanol (98%, 5 mg g(-1)d(-1)). The optimum concentration of methanol required, for stable dechlorination of THCH (100 mg l(-1)) in the UASB reactor, was found to be 500 mg l(-1). Results indicate that addition of methanol as electron donor enhances dechlorination of THCH at high inlet concentration, and is also required for stable UASB reactor performance.

A novel immobilised bioreactor has been developed especially for the treatment of pollutants characterized by high volatility alongwith high water solubility and low microbial yields. The new bioreactor referred to as the rotating rope bioreactor (RRB) provides higher interfacial area (per unit reactor liquid volume) along with high oxygen mass transfer rate, greater microbial culture stability; and consequently higher substrate loadings and removal rates in comparison to other conventional rectors for the treatment of volatile compounds. Pyridine was used as a model compound to demonstrate the enhanced performance with RRB, when compared to that reported with other conventional bioreactors. The experimental results indicate that the novel RRB system is able to degrade pyridine with removal efficiency of more than 85% at higher pyridine concentration (up to 1000 mg/l) and loading [up to 400 mg/m 2 /h (66.86 g/m 3 /h)], with a shorter hydraulic retention time (9–18 h). The reactor has been in operation for the past 15 months and no loss of activity has been observed.

Waste activated sludge generated from a combined dairy and food processing industry wastewater treatment plant was evaluated for its potential to produce biodegradable plastic, poly beta-hydroxybutyric acid (PHB). Deproteinized jowar grain-based distillery spentwash yielded 42.3% PHB production (w/w), followed by filtered rice grain-based distillery spentwash (40% PHB) when used as substrates. Addition of di-ammonium hydrogen phosphate (DAHP) resulted in an increase in PHB production to 67% when raw rice grain-based spentwash was used. Same wastewater, after removal of suspended solids by filtration and with DAHP supplementation resulted in lower PHB production (57.9%). However, supplementing other wastes with DAHP led to a substantial decrease in PHB content in comparison to what was observed in the absence of DAHP.

Biodegradability of technical grade hexachlorocyclohexane (tech-HCH) was studied in an upflow anaerobic sludge blanket reactor (UASB) under continuous mode of operation in concentration range of 100-200 mg/l and constant HRT of 48 h. At steady state operation more than 85% removal of tech-HCH (upto 175 mg/l concentration) and complete disappearance of beta-HCH was observed. Kinetic constants in terms of maximum specific tech-HCH utilization rate (k) and half saturation velocity constant (K(L)) were found to be 11.88 mg/g/day and 8.11 mg/g/day, respectively. The tech-HCH degrading seed preparation, UASB reactor startup and degradation in continuous mode of operation of the reactor is presented in this paper.

Most of the excess sludge from a wastewater treatment plant (60%) is disposed by landfill. As a resource utilization of excess sludge, the production of biodegradable plastics using the sludge has been proposed. Storage polymers in bacterial cells can be extracted and used as biodegradable plastics. However, widespread applications have been limited by high production cost. In the present study, activated sludge bacteria in a conventional wastewater treatment system were induced, by controlling the carbon: nitrogen ratio to accumulate storage polymers. Polymer yield increased to a maximum 33% of biomass (w/w) when the C/N ratio was increased from 24 to 144, where as specific growth yield decreased with increasing C/N ratio. The conditions which are required for the maximum polymer accumulation were optimized and are discussed.

The present study investigates the use of defatted algal biomass (DAB) as a non-conventional low cost adsorbent. The maximum adsorption capacity of biomass (raw, defatted and sulfuric acid pretreated DAB) was determined by liquid phase adsorption studies in batch mode for the removal of methylene blue present at various concentrations (1, 2, 3, 4, and 5 mg L (1)) from aqueous solutions. The data was well fitted with Langmuir and Freundlich isotherms. The maximum adsorption capacity for raw, defatted and sulfuric acid pretreated DAB was found to be 6.0, 7.73 and 7.80 mg g (1), respectively. The specific surface area of raw, defatted and sulfuric acid pretreated DAB was estimated to be 14.70, 18.94, and 19.10 m(2) g (1), respectively. To evaluate the kinetic mechanism that controls the adsorption process, pseudo-first order, pseudo-second order, intraparticle diffusion and particle diffusion has been tested. The data fitted quite well with pseudo-second order kinetic model. (C) 2014 Elsevier Ltd. All rights reserved.

The present study analyzes the effect of thermal pretreatment for enhancing the biomethane potential of defatted algal biomass of Scenedesmus dimorphus through statistically guided experimental design. To this end, defatted microalgal biomass at various concentrations (1, 3 and 5 g L-1) was pretreated at elevated temperatures (100, 120 and 150 degrees C) for 20, 40 and 60 min. The solubilised TOC was favourably enhanced up to 71 mg L-1 after pretreatment at a temperature of 150 degrees C for reaction time of 60 min. The methane yield was substantially enhanced (up to 60%) and could be correlated with an increase in organic matter solubilisation and enhanced biodegradability via thermal pretreatment. The optimisation of the integrated thermal pretreatment-biomethanation process resulted in up to 1.6-fold increase in methane yield. (C) 2014 Elsevier Ltd. All rights reserved.

The effluents from molasses-based distilleries after biomethanation are beset with problems of intensified dark brown color, high residual COD, low biodegradability index (BOD/COD ratio

In this study, an attempt was made to use micro-algal system for the production of biodiesel precursors and simultaneous CO 2 mitigation. Chlorella sp. was found to have a higher growth rate as compared to the other algal species tested namely Chlamydomonas sp. and Synnecococcus sp. At different CO 2 concentrations (0.03%, 3%, 10% and 15%), the lipid productivity was 23.0, 20.0 and 27.3 mg/L/d respectively. Calcite produced was characterized using FT-IR, SEM and XRD. The FAME in crude biofuel was analyzed by GC-FID that found to contain palmitic acid (C16:0), docosapentaenoic acid (C22:5) and docosahexaenoic acid (C22:6). The calorific value of Chlorella sp. was found to be 29 kJ/g which is higher than values reported for fresh water microalgae making it a potential candidate to be used as an alternate fuel.

Biological treatment of dimethyl sulphide (DMS) was investigated in a bench-scale biofilter, packed with compost along with wood chips, and enriched with DMS degrading microorganism Bacillus sphaericus . The biofilter could remove 62–74% of the inlet DMS, at an optimum loading of 0.484 g/m 3 /h with optimum empty bed contact time (EBCT) of 384 s and an average moisture range of 65–70%. The biodegradative products of DMS were sulphide, thiosulphate and sulphate. Evaluation of microbiological status of the biofilter indicated the presence of other bacterial cultures viz. Paenibacillus polymyxa , and Bacillus megaterium , besides B. sphaericus .

Waste gas containing diethyldisulphide (DEDS) is generated from various industries including pulp and paper, refinery, rayon and molasses based distilleries, etc. DEDS has odour threshold detection with an average concentration of 10 −9 mg/m 3 at 25 °C. DEDS is toxic to bacteria, fungus and also to mammals when exposed for a long period. Waste gas containing DEDS require proper treatment prior to discharge into the environment. DEDS containing waste gas was treated in a biofilter, packed with compost along with wooden chips and enriched with DEDS degrading microorganisms. The biofilter could remove DEDS to the extent of 94 ± 5% at a loading of 1.60 g/m 3 /h with an empty bed retention time of 150 s. At optimal operating conditions, the average moisture content required by the biofilter was in the range of 60–65%. The biodegradative products of DEDS were thiosulphate and sulphate.

A steady model for the evaluation of external liquid film diffusion and internal pore diffusion effects in an immobilized biofilm system under continuous mode of operation was developed. The model takes into account, substrate diffusion through external liquid film and biofilm. Average rate of substrate consumption in the biofilm was considered. The overall efficiency of the biofilm was mathematically represented by considering the combined effects of substrate penetration and substrate utilization in the biofilm. The model was illustrated using a case study of pyridine biodegradation in a rotating biological contactor immobilized with pyridine degrading microbial film. The model is able to effectively predict both internal and external mass transfer effects in an immobilized biofilm system.