SEQUENTIAL ANAEROBIC AND AEROBIC TREATMENT OF PULP AND PAPER MILL EFLUENT

Abstract

Paper mill is one of the major sources of pollution causing industry with intensely coloured effluent. The effluent is rich in lignocellulosic materials and other chemicals used during manufacturing which results in high Bio-chemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). Due to its high toxic and mutagenic nature when discharged untreated there is a growing demand to treat the effluent before discharge. Biological treatment is a promising technique as it greatly reduces colour, BOD and COD. Various fungal and bacterial species are capable of degrading the lignocellulosic materials present in the effluent. In the present study characterization of the paper mill effluent and identification of the degradation efficiency of lignin degrading fungal species - Pleurotus species and Rhizopus stolonifer and bacterial species – Pseudomonas aeruginosa and Bacillus subtilis in laboratory scale was done. Here sequential anaerobic and aerobic treatment was carried out in two bioreactors in series. The study indicated that anaerobic treatment gave a reduction of colour (18%), lignin (25%), COD (36%), BOD (28%) in 5days. The anaerobically treated effluent was then separately given to the aerobic reactors containing the fungal and bacterial species. Data obtained indicated that the Rhizopus showed good reduction in colour (71%), lignin (77%), COD (68%) and BOD (70%) in 5days whereas Pleurotus, Pseudomonas and Bacillus species showed reduction in colour (68%, 31%, 18%), lignin (64%, 43%, 44%), COD (58%, 42%, 43%) and BOD (60%, 40%, 42%) respectively in 5days. Thus Rhizopus was identified as the microbe with better degradation capacity.