K.V. Padoley

Bioreactors for treatment of VOCs and odours – A review

Volatile organic compounds (VOCs) and odorous compounds discharged into the environment create ecological and health hazards. In the recent past, biological waste air treatment processes using bioreactors have gained popularity in control of VOCs and odour, since they offer a cost effective and environment friendly alternative to conventional air pollution control technologies. This review provides an overview of the various bioreactors that are used in VOC and odour abatement, along with details on their configuration and design, mechanism of operation, insights into the microbial biodegradation process and future R&D needs in this area.

Cavitationally induced biodegradability enhancement of a distillery wastewater

Hydrodynamic cavitation (HC) was evaluated as a pretreatment option for the complex/recalcitrant biomethanated distillery wastewater (B-DWW). The effect of various process parameters such as inlet pressure, dilution and reaction time on reduction of COD/TOC and enhancement of biodegradability index (BI:BOD(5):COD ratio) of the B-DWW was studied with an aim to maximize the biodegradability index and reducing the toxicity of the distillery wastewater. It was observed that higher operating pressure (13 bar) yielded the maximum BI whereas the lower pressure (5 bar) is suitable for the reduction in the toxicity of B-DWW. The toxicity of the distillery wastewater was analyzed by measuring the COD, TOC and color of the wastewater sample. The HC pretreatment under optimized conditions leads to a BI of 0.32, COD and TOC reduction of 32.24% and 31.43%, respectively along with a color reduction by 48%. These results indicate the potential of HC as a pretreatment option for enhancing the biodegradability index of the recalcitrant wastewater such as B-DWW along with reduced toxicity of wastewater as observed from COD, TOC and color reduction profile under optimized conditions.

Wet air oxidation as a pretreatment option for selective biodegradability enhancement and biogas generation potential from complex effluent.

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.

Wet air oxidation induced enhanced biodegradability of distillery effluent.

The present study reports the feasibility of Wet Air Oxidation (WAO) as a pretreatment option for enhanced biodegradation of complex distillery effluent. Initially, the distillery effluent was pretreated by WAO at different process conditions (pressure, temperature and time) to facilitate enhancement in the biodegradability index (BIxa0=xa0BOD5: COD ratio). The biodegradability of WAO pretreated effluent was evaluated by subjecting it to aerobic biodegradation and anaerobic followed by aerobic biodegradation. Aerobic biodegradation of pretreated effluent with enhanced biodegradability index (BIxa0=xa00.4-0.8) showed enhanced COD reduction of up to 67.7%, whereas the untreated effluent (BIxa0=xa00.17) indicated poor COD reduction of only 22.5%. Anaerobic followed by aerobic biodegradation of pretreated effluent has shown up to 87.9% COD reduction, while the untreated effluent has shown only 43.1% COD reduction. Bio-kinetic parameters also confirmed the increased rate of bio-oxidation at enhanced BIs. The results indicate that the WAO pretreatment facilitates enhanced bio-oxidation/bio-degradation of complex effluents like the distillery spent wash.

Microbial degradation of pyridine and α-picoline using a strain of the genera Pseudomonas and Nocardia sp.

Biodegradation of pyridine and α-picoline (2-methyl pyridine) by Pseudomonaspseudoalcaligenes-KPN and Nocardia sp. isolated from garden soil were investigated in batch culture experiments. Pyridine and α-picoline (50–200xa0mgxa0L−1) were used as sole source of carbon and energy in the investigation. The kinetic constants were evaluated for pyridine and α-picoline degradation under optimized nutritional (C, N, P) and environmental (pH, temperature) conditions. The values of bio-kinetic constant obtained in the present investigation indicate the usefulness of both the cultures for treatment of waste containing pyridine and its derivatives.

Biotreatment of waste gas containing pyridine in a novel rotating rope biofilter.

A novel Rotating Rope Biofilter (RRB) has been developed especially for the treatment of Volatile Organic Compounds (VOCs) at higher loadings and characterised by high volatility along with high water solubility. The RRB provides a 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 with other conventional reactors (e.g. biofilters) widely used for the treatment of VOCs. Pyridine was used as a model compound to demonstrate the enhanced performance of the RRB. The experimental results indicate that the novel RRB system is able to degrade pyridine with removal efficiency of more than 90%, up to a loading of 250 g/m³/h. The reactor has been in operation for the past 15 months and no loss of activity has been observed.