R.S. Singh

Biofiltration of toluene using wood charcoal as the biofilter media.

A laboratory scale biofilter inoculated with Pseudomonas putida (MTCC 102) was used for degradation of toluene present in air. Wood charcoal was used as the filter media and a layer of glass beads (6mm) was used for improved air distribution. The biofilter was operated continuously for a period of 5months at four different flow rates - 0.06, 0.12, 0.18, and 0.24m(3)h(-1), with inlet concentration of toluene ranging from 0.04 to 4.5gm(-3). Air having toluene vapor was fed to the biofilter at various loadings ranging from 30.6 to 1104.5gm(-3)h(-1). The removal efficiency was obtained in the range of 70-99.5%. The maximum elimination capacity of 872.5gm(-3)h(-1) was observed at the inlet load of 1104.5gm(-3)h(-1). Wood charcoal was found to an effective biofilter media for toluene biodegradation.

Biodegradation of chlorpyrifos by Pseudomonas sp. in a continuous packed bed bioreactor.

Biodegradation of chlorpyrifos (CP) by Pseudomonas (Iso 1) sp. was investigated in batch as well as continuous bioreactors packed with polyurethane foam pieces. The optimum process parameters for the maximum removal of CP, determined through batch experiments, were found to be: inoculum level, 300×10(6)CfumL(-1); CP concentration, 500mgL(-1); pH 7.5; temperature, 37°C and DO, 5.5mgL(-1). The continuous packed bed bioreactor was operated at various flow rates (10-40mLh(-1)) under the optimum conditions. The steady state CP removal efficiency of more than 91% was observed up to the inlet load of 300mgL(-1)d(-1). The bioreactor was sensitive to flow fluctuations but was able to recover its performance quickly and exhibited the normal plug-flow behavior. Accumulation of TCP (3,5,6-trichloro-2-pyridinol) affected the reactor performance.

Kinetics of bio-filtration of trichloroethylene by methanotrophs in presence of methanol.

The biodegradation of TCE was studied in a laboratory scale biofilter packed with wood charcoal and inoculated with mixed culture of methanotrophs isolated from local soil. The removal efficiency was found to be higher than 90% up to an inlet load of 5.1g/m(3)h. The maximum elimination capacity was 6.7g/m(3)h at an inlet loading rate of 11.3g/m(3)h. The reaction constants EC(max,)K(s) and K(i) calculated from the experimental results are also presented. The biodegradation process is found to be inhibited at higher TCE concentration. The carbon dioxide production rate has been found to be a linear function of elimination capacity. The DNA finger printing techniques has indicated the presence of functionally active methanotrophic community including Methylocystis sp. in the biofilter.

Removal of hydrogen sulfide generated during anaerobic treatment of sulfate-laden wastewater using biochar: Evaluation of efficiency and mechanisms

Removal of hydrogen sulfide (H2S) from biogas was investigated in a biochar column integrated with a bench-scale continuous-stirred tank reactor (CSTR) treating sulfate-laden wastewater. Synthetic wastewater containing sulfate concentrations of 200-2000mg SO42-/L was used as substrate, and the CSTR was operated at an organic loading rate of 1.5g chemical oxygen demand (COD)/L·day and a hydraulic retention time (HRT) of 20days. The biochar was able to remove about 98.0 (±1.2)% of H2S for the ranges of concentrations from 105-1020ppmv, especially at high moisture content (80-85%). Very high H2S adsorption capacity (up to 273.2±1.9mg H2S/g) of biochar is expected to enhance the H2S oxidation into S0 and sulfate. These findings bring a potentially novel application of sulfur-rich biochar as a source of sulfur, an essential but often deficient micro-nutrient in soils.

Degradation kinetics of chlorpyrifos and 3,5,6-trichloro-2-pyridinol (TCP) by fungal communities.

Fungal isolates obtained from soil were used for degrading chlorpyrifos (CP) and TCP. The percentage degradation ranged from 69.4 to 89.8 for CP and 62.2 to 92.6 for TCP after one week. The values of K(s) and V(max) were different for different isolates. The K(s) ranged from 66.66 to 169.5mg/L and V(max) from 6.56 to 40.4 mg/L/d for CP and from 53.19 to 163.9 mg/L and 3.41 to 40.40 mg/L/d, respectively, for TCP. Fungal community showed high affinity for both CP and TCP. The genetic relatedness of isolate F1 to Aspergillus sp., F2 and F3 to Penicillium sp., F4 to Eurotium sp. and F5 to Emericella sp. were confirmed. The degradation potential was in the order: F1>F2=F3>F4>F5.

Bio-filtration of trichloroethylene using diazotrophic bacterial community

Biodegradation of TCE was studied in a biofilter packed with wood charcoal and inoculated with diazotrophic bacterial community isolated from local soil. Steady state TCE removal efficiencies higher than 85% were observed up to inlet load of 2.866 g m(-3) h(-1). The maximum elimination capacity of 5.31 g m(-3) h(-1) was observed at an inlet load of more than 7.90 g m(-3) h(-1). The biofilter was sensitive to fluctuations in the process conditions but could easily recover its performance after 10 days shutdown. Almost constant and small pressure drop per unit length and very negligible compaction was observed during the whole experimental period. The molecular analyses such as RT-PCR and gene sequencing revealed the presence of functionally active Azospirillum species in the biofilm.

Kinetic studies on degradation of Reactive Red 120 dye in immobilized packed bed reactor by Bacillus cohnii RAPT1

The degradation of Reactive Red 120 using Bacillus cohnii RAPT1 immobilized on polyurethane was studied. Initial experiments indicated that the percentage removal of dye in immobilized batch was significantly higher than batch (without immobilization). The optimum process parameters such as effect of dye concentration, time of immobilization on Poly Urethane Foam, initial inoculum size, pH and temperature for removal of dye were investigated and was found as 200ppm, 36h, 300*10(6) colony forming units/ml, 8.0 and 35°C respectively. Under optimum conditions, 100% removal of dye was obtained within 4h. The kinetics of biodegradation for the batch with free cells and immobilised packed batch was found to be IInd order with kinetic constant and initial rate of reaction as 0.0408, 0.084L/(mgday) and 1632, 3360 (mg/Lday) respectively.

Performance evaluation of Malathion biodegradation in batch and continuous packed bed bioreactor (PBBR)

The aim of this work was to study the biodegradation of Malathion in batch and continuous packed bed (Polyurethane foam; PUF) bioreactor (PBBR). After 10days, 89% Malathion removal was observed in batch PBBR. Continuous PBBR was operated at various flow rates (5-30mL/h) under optimum condition over a period of 75days. Inlet loading rates and elimination capacities were observed in the range of 36-216 and 7.20-145.4mg/L/day with an average removal efficiency of more than 90% under steady state conditions. GC/MS analysis confirms phosphorodithionicacid,O,O,S-trimethylester and diethylmercaptosuccinate as metabolites. Biodegradation of Malathion under inhibitory and non-inhibitory conditions was studied using Monod and Andrew-Haldane models and the kinetic constants were calculated and found to be μmax: 0.271 per day; Ks: 126.3mg/L using Monod and μmax: 0.315 per day; Ks: 151.32mg/L; Ki: 594.75mg/L using Andrew-Haldane models.

Recent advancements in bioremediation of dye: Current status and challenges

The rampant industrialization and unchecked growth of modern textile production facilities coupled with the lack of proper treatment facilities have proliferated the discharge of effluents enriched with toxic, baleful, and carcinogenic pollutants including dyes, heavy metals, volatile organic compounds, odorants, and other hazardous materials. Therefore, the development of cost-effective and efficient control measures against such pollution is imperative to safeguard ecosystems and natural resources. In this regard, recent advances in biotechnology and microbiology have propelled bioremediation as a prospective alternative to traditional treatment methods. This review was organized to address bioremediation as a practical option for the treatment of dyes by evaluating its performance and typical attributes. It further highlights the current hurdles and future prospects for the abatement of dyes via biotechnology-based remediation techniques.

Characterization of bacterial isolates from rubber dump site and their use in biodegradation of isoprene in batch and continuous bioreactors

Bacterial isolates from contaminated soil of a waste rubber dumping site were isolated and characterized using biochemical and molecular approaches. Isoprene degradation kinetics in batch mode (isoprene concentration: 100-1000 ppm) revealed the degradation efficiency of isolates as: Pseudomonas sp. (83%)>Alcaligenes sp. (70%)>Klebsiella sp. (68.5%). The most efficient isolate Pseudomonas sp. was finally inoculated in a specifically designed bioreactor system comprising a bioscrubber and a biofilter packed with polyurethane foam connected in series. The bioscrubber and biofilter units when operated in a series showed more than 90% removal efficiency up to the inlet loading rate (IL) of 371.1g/m(3)/h. Maximum elimination capacity (EC) of biofilter was found to be an order of magnitude greater than that for bioscrubber. Oxidative cleavage of the double bond of isoprene has been revealed through IR spectra of the leachate.