Anaerobic treatment of atrazine bearing wastewater

Performance of mixed microbial anaerobic culture in treating synthetic wast ewater with high Chemical Oxygen Demand (COD) and varying atrazine concentr ation was studied. Performance of hybrid reactors with wood charcoal as ads orbent, with a dose of 10 g/l and 40 g/l, along with the microbial mass was also studied. All the reactors were operated in sequential mode with Hydra ulic Retention Time (HRT) of 5 days. In all the cases, COD removal after 5 days was found to be above 81%. Initial COD was above 1000 mg/l. From a hyb rid reactor COD removal after 2 days was observed to be 90%. Atrazine reduc tion after 5 days by microbial mass alone was 43.8%, 40% and 33.2% with an initial concentration of 0.5, 1.0 and 2.0 mg/l respectively. MLSS on all th e cases were almost same. Increasing MLSS concentration by about 2 fold did not increase the atrazine removal efficiency significantly. Maximum atrazi ne removal was observed to be 64% from the hybrid reactor with 10 g/l of wo od charcoal and 69.4% from the reactor with 40 g/l of wood charcoal. Atrazi ne removal from the hybrid reactors after 15 days were observed to be 35.7% and 38.7%, which showed that the higher dose of wood charcoal in hybrid re actor did not improve the atrazine removal efficiency significantly. Specif ic methanogenic activity test showed no inhibitory effect of atrazine on me thane producing bacteria. The performance of anaerobic microorganisms in re moving atrazine with no external carbon source and inorganic nitrogen sourc e was studied in batch mode. With an initial concentration of 1.0 mg/l, red uction of atrazine by the anaerobic microorganisms in absence of external c arbon source after 35 days was observed to be 61.8% where as in absence of external carbon and inorganic nitrogen source the reduction was only 44.2% after 150 days. Volatilization loss of atrazine was observed to be insignif icant.