In this research, the domestic wastewater was treated by full-scale Biolak/A2O process. The effects of dissolved oxygen (DO) on nitrogen and phosphorus removal of the system in oxic zone were investigated. Controlling to DO at 0.8-1.5 mg/L, the treatment efficiency of system was near optimal with the total nitrogen efficiency of 69.45%. The simultaneous nitrification and denitrification could be achieved under this condition. Based on the calculation equations and transformation pathways of nutrients, about 23.71% total nitrogen (TN) was removed by multistage A/O system in the oxic tank. When DO was 1.0-3.0mg/L, the total phosphorus (TP) removal efficiency was the highest at 73.97%. DO in the range of 1.0-1.5mg/L was optimal for the nutrient removal in Biolak/A2O process, removal efficiency of TN and TP were 68.87% and 73.68%. TN and TP of the effluent were 12.02mg/L and 0.95mg/L, respectively.

Fly ash and sludge are all solid waste. With fly ash as an additive, sludge is composted in aerobic condition, which can achieve agricultural requirements. After testing, we find that the activity of fly ash can be promoted and stimulated by adding different proportions of activator under alkaline conditions, which has a low activity under conventional conditions. Adding slow-releasing additive, fertility of sludge may keep longer, which has a certain reference value to agricultural fertilizer production.