Nitrogen removal from domestic sewage by algae-Daphnia food chain system

Abstract

A type of domestic sewage, rice-washed water from an institutional kitchen, and artificial sewage were treated with three steps of processes; activated sludge, algal culture, and $\underline{Daphnia}$ culture. Through the activated sludge process 89% of COD, 60% nitrogen and 16% of phosphorus were removed from artificial sewage. Through the cultures of algae and $\underline{Daphnia}$, further reductions of nitrogen and phosphorus could be achieved. About 97% of the nitrogen in the secondary effluent was stripped by algal assimilation. $\underline{Daphnia}$ in turn removed 87% of the algae, but regenerated 20% of the nitrogen originally incorporated in the algal cells, so that the total inorganic nitrogen removal efficiency of the system was 67%. The process has the capability of being expanded to include additional food chain in an integrated and highly controlled food chain system to play the dual role of wastewater treatment and food production.