BIOLOGICAL DENITRIFICATION OF WASTEWATER IN A FLUIDIZED BED BIOREACTOR BY IMMOBILIZATION OF PSEUDOMONAS STUTZERI USING POLY PROPYLENE GRANULES

Nitrate is a major pollutant present in effluent wastewater from nitrogenous fertilizer, explosives, paper mills, pulp mills, and also from municipal waste. Nitrate is harmful to both mankind and animal and also to the environment. The World Health Organization has set a limit of 10 mg/L NO3- for human consumption and 100 mg/l NO3- for animals. Water above these limits requires denitrification. Nitrates causes cancer, blue-bay syndrome, hypertension and thyroid hypertrophy. Experimentation on biological denitrification was carried out in a fluidized bed bio-reactor using synthetic wastewater with polypropylene beads as supporting media for the growth of microorganism. Synthetic wastewater is taken into the reactor for biological treatment and air was fed from bottom with solids being fluidized at the top due to low density. Experiments were performed for water of different initial nitrate concentrations with Pseudomonas stutzeri microorganism by varying the parameters like airflow rate, temperature, carbon source, poly propylene beads and pH in the range 2 lpm to 3.5 lpm, 20 0C to 35 0C, 70 mg/L to 85 mg/L, 5 mg/L to 25 mg/L and 6 to 8 respectively. The optimum parameters at which maximum denitrification is noticed are found to be 2.5 lpm (air flow rate), 30 0C (temperature), 85 mg/L (carbon source), 15 mg/L (poly propylene beads) and 7 (pH). More than 95% removal of nitrates is noticed from the experimental work. The objective of the study is to investigate the effect of operating parameters like airflow rate, temperature, carbon source, polypropylene beads and pH.