Treatment of piggery wastewater in experimental high rate algal ponds

The objective of this work was to evaluate the efficiency of high rate algal ponds (HRAP) for the treatment of piggery wastewater pretreated with an electroflocculation system. Experiments were conducted in two experimental raceway ponds with a surface area of 1.54 m2 and a water depth of 0.26 m. The efficiency of both ponds was compared as a function of the surface organic loading rate and ammonia loading rate. Pretreated piggery wastewater had average COD and ammonia concentrations of 3000 mgO2/L and 790 mgNH4+-N/L, respectively. The COD removal was 90 % with an organic loading equal to or below 20 g O2/m2d. The ammonia removal was 90 % with an ammonia load of 2.5 gNH4+-N/m2d, however it decreased throughout the experiments when ammonia accumulated in the mixed liquor. Simultaneous COD and ammonia removal was limited by ammonia removal. From a mass balance it was determined that the main pathway for ammonia removal was nitrification.Peer ReviewedPostprint (author's final draft