improving osa process efficiency in sludge production reduction in sbr

osa (oxic settling anoxic) process is one of the sludge reduction methods. in this method an anaerobic reactor is placed in activated sludge recycling line for sludge reduction purpose. this method is getting popular because of possibility of its application in currently operating waste water treatment plants. in this research, the performance of osa process in sludge reduction in sbr was improved through thermal and mechanical treatment of recycling activated sludge. an experimental pilot was developed for this purpose. sludge was warmed up to 50, 70 and 90 ◦c. a mechanical mixer with different voltages was used for mechanical treatment of sludge. by application of osa process the sludge production was reduced up to 24% and cod removal efficiency was reduced from 90% to 86%. after thermal treatment the sludge production was reduced up to 48%. the sludge reduction would decrease to 34% when mechanical treatment is employed. application of osa method does not highly affect the effluent quality based on tss and cod indicators, but the effluent quality is reduced in case of mechanical and thermal treatment