Bioremediation of nitroexplosive wastewater by an yeast isolate Pichia sydowiorum MCM Y-3 in fixed film bioreactor.

Nitroexplosives are essential for security and defense of the nation and hence their production continues. Their residues and transformed products, released in the environment are toxic to both terrestrial and aquatic life. This necessitates remediation of wastewaters containing such hazardous chemicals to reduce threat to human health and environment. Bioremediation technologies using microorganisms become the present day choice. High Melting Explosive (HMX) is one of the nitroexplosives produced by nitration of hexamine using ammonium nitrate and acetic anhydride and hence the wastewater bears high concentration of nitrate and acetate. The present investigation describes potential of a soil isolate of yeast Pichia sydowiorum MCM Y-3, for remediation of HMX wastewater in fixed film bioreactor (FFBR). The flask culture studies showed appreciable growth of the organism in HMX wastewater under shake culture condition within 5-6 days of incubation at ambient temperature (28 +/- 2 degrees C). The FFBR process operated in both batch and continuous mode, with Hydraulic Retention Time (HRT) of 1 week resulted in 50-55% removal in nitrate, 70-88% in acetate, 50-66% in COD, and 28-50% in HMX content. Continuous operation of the reactor showed better removal of nitrate as compared to that in the batch operation, while removal of acetate and COD was comparable in both the modes of operation of the reactor. Insertion of baffles in the reactor increased efficiency of the reactor. Thus, FFBR developed with baffles and operated in continuous mode will be beneficial for bioremediation of high nitrate and acetate containing wastewater using the culture of P. sydowiorum.

Combined effect of plate pulsation parameters and phenol concentrations on the phenol removal efficiency of a pulsed plate bioreactor with immobilized cells.

Continuous aerobic biodegradation of phenol in synthetic wastewater with phenol at different concentrations (200, 300, 500, 800 and 900 ppm) was carried out in a pulsed plate column, which is used as a bioreactor with immobilised cells of Nocardia hydrocarbonoxydans (NCIM 2386) at a dilution rate of 0.4094 h(-1) and amplitude of 4.7 cm at various frequencies of pulsation (0, 0.25, 0.5, 0.75 and 1 s(-1)). The effect of frequency of pulsation on the steady state performance of the bioreactor for phenol biodegradation at different influent concentrations was studied. Percentage degradations were observed to be a combined effect of volumetric phenol loading, reactor residence time, mass transfer limitations and phenol inhibition effect. At 500 ppm influent phenol concentration the effect of frequencies of pulsation on the steady state percentage degradation at different amplitudes was studied. The percentage degradation increased with increase in frequency and almost 100% degradation was achieved at 0.75 s(-1), 0.5 s(-1) or 0.25 s(-1), with 3.3, 4.7 or 6.0 cm amplitudes respectively and hence the vibrational velocity (amplitude*frequency) was found to influence the steady state performance of the reactor. It was found that optimum vibrational velocities need to be fixed for maximum removal efficiency of the bioreactor depending on the influent phenol concentration.