More and more evidence show that nitrogen and phosphorus in discharged municipal wastewater are the main reasons for the entrophication of water bodies, and biological nitrogen and phosphorus removal from wastewater are the most important technologies for controlling entrophication. But the traditional biological nitrogen (N) and phosphorus (P) removal processes are complicated technologically and operationally with high running cost, which limited its application. With the characteristics of biofilm and activated sludge, a new hybrid biofilm-activated sludge system will be studied to enhance its ability for simultaneous removal of N and P. According to oxygen diffusion theory, aerobic, anoxic and anaerobic conditions can be formed in the biofilm by optimizing installation of biofilm carriers and air diffusers, controlling DO, SRT and recycle ratio in the system to make DPAOS (denitrifying phosphorus accumulation organisms) dominate in the system. DPAOS can remove P using nitrates formulated from nitrification under anoxic condition in the biofilm, so P removal through denitrification achieved in the hybrid system, which will reduce running cost efficiently and simplify operation, as well as encourage N and P removal. Material exchange and relationships between biofilm exfoliated and activated sludge attachment, changing characteristics of population structure of microbes, and relations between biofilm and activated sludge all will be studied. Finally, a simulation model for hybrid biofilm-activated sludge system will be built according to the substrate removal kinetics and microbial growth dynamics in the system.

Performing Organization: Institute of Urban Environment, CAS
Sponsor: Chinese Academy of Sciences
Headed by Wang Shumei and Shi Jianwen
Start Date: 2007.11
End Date: 2009.11