The Research Of Artificial Zeolite-Coal Slag Double-layer Medium Biological Aerated Filter For Municipal Wastewater

The shortage of water resources is very grim in modern China. It is the most important way that the municipal wastewater should be recycled to reduce the contradiction of using water. Comparing with the other treatment technology, Biological Aerated Filter (BAF) has many advantages such as simple structure, hand manipulation, high processing efficiency, low operation cost and so on. The paper focus on the coal slag- zeolite double layer medium BAF for municipal wastewater. It includes start-up of the filter under condition of natural temperature, and performance of the filter treating municipal sewage under some hydraulic load and the effects of the parameters: the ratio of air and water correlated to the filter.(1) Coal slag- zeolite double layer medium BAF could keep the removal rate of COD_Cr, NH₃-N in staying a high stage. In intake water, the average cotent of COD_Cr < 125 mg/L, NH₃-N<11mg/L under the best parameters.(2)Coal slag and Artificial zeolite have big voidage. The factor in favor of forming biofilm and aerate. They have good chemical and biological stability, mechanical strength. The match of coal slag-artificial zeolite is first choice.(3)The experiment carry out style of upward flow and aeration constantly under 20℃. The gas water ratio should be increased from 1/2 to 1.25/1. After 24 days, the removal rate of NH3-N arrived at about 60%, the forming biofilm finished.(4)The results demonstrate: the gas water of 2/1 and HRT of 12 hours is the best situation. The removal rate of COD_Cr , NH₃-N is averaged at 80%, 70% respectively. The temperature is a important factor to influence result and the appropriate data is 20 ℃. COD_Cr , NH₃-N, SS could be removed very well under this temperature. The experiment is very hard to remove phosphor. The best backwash cycle is 6 hours and use air water backwashing. The treatment efficiency could come back to 70% after 12 hours behind the backwash.(5)The removal rate of double-layer medium BAF is better. The removal rate of COD_Cr and NH₃-N are improved to 10% and 30% respectively comparing with mono layer BAF.