Polyacrylamide wastewater treatment in a nested biofilm airlift suspension reactor

Polyacrylamide has been widely used in tertiary oil recovery. Oilfield produced water in a large scale contain polyacrylamide, leading to oilfield environment pollution. In this paper, the nested loops biofilm airlift suspension reactor was used in polyacrylamide wastewater treatment. In the reactor, wastewater can alternately flow through the hypoxic environment fixed light carriers and aerobic environment suspended walnut shell biological carriers, achieving simultaneous removal of organic matter and nitrogen. The influencing factors on the organic compound degradation and denitrification performance were studied. Biological and hydrodynamic model of nitrogen and carbon removal was established. Also, the biological phase structure of the carrier biofilm was observed. The results show that polyacrylamide degradation and ammonia nitrogen removal rate are around 30% and 95%, respectively when the experimental hydraulic retention time is 24h. Due to poor denitrification efficiency; nitrate removal rate is only 20%. The carrier biofilm thickness is appropriate, and filamentous bacteria occupy the dominant position.