Study On Vertical Flow Filter Dealing With Rural Sewage

With the comprehensive and thorough construction,the new rural has undergone enormous changes and rural residents'living standards keep on improving. At the same time, water consumption of the rural residents has shown a trend of substantial growth which results in the sharply jump of rural household wastewater discharge amount.Lacking of wastewater collection and supporting treatment facilities, amount of wastewater was discharged and flew onto the streets before effective collection and treatment. The rural wastewater led to the mosquito and flies'breeding and village environmental pollution which eventually triggered water and soil environmental pollution and reduced the rural residents',comfort level of life ; what's more, they may do harm to the residents'physical and spiritual health. Consequently, it is the rural sewage problem that not only has become the key factor which determines the new rural construction's success or failure, but also become the focus of related government, experts and scholars and the public as a matter of fact.Therefore,taking the rural domestic wastewater as research object, given the characteristics of effluent discharge, firstly,we put forward some methods of sewage collection , including headstream division, dispersed collection, centralized collection and draining into the municipal pipe network ;secondly, on account of the features of sewage, we compared and analyzed the comprehensive technologies of wastewater treatment which is suitable for rural application, such as biogas pit technology , constructed wetlands technology, stabilization pond technology and ecological technology ; finally, considering the rural life style, we analyzed the reason for wastewater collection dilemma and found that the reason lied in two aspects: space casualness and time dispersion. furthermore, we put forward a wastewater treatment technics called vertical flow filter which can guide the fixed-point collection of rural sewage and reduce the concentration of pollutants at the same time .Besides ,we studied the operation parameters which is suitable for northern rural domestic sewage , aiming at achieving the low-cost collection ,resourceful usage , solving human health damage and environmental problems caused by wastewater pollution.Vertical flow filter takes the mechanism of rapid biological filter for reference, combining physical filtration and adsorption with bio-oxidation and degradation.It can subtract the main pollutants in domestic sewage under the condition of low power consumption.During the research, static adsorption to phosphorus of three filter materials was investigated firstly, then study focused on the remove effection of NH₄⁺-N,TP,COD_cr in vertical flow filter filled with different filter materials.The static adsorption test indicated that slags, river sands and ceramsite have similar static adsorption characteristic to phosphorus. Under the test conditions, original concentration of phosphorus (120mg/L) is the saturated limit value of filter materials ,if less than the value,the concentration of phosphorus will be the restrictive condition of the static adsorption; in addition,among this three filter materials, the adsorption effect of ceramsite to phosphorus is much better than slags and river sands.The experiment of the vertical flow filter on the removal of COD_cr,TP and NH₄⁺-N under different conditions indicate that :â‘ on the condition of hydraulic loading of 0.35m³/m².d, no filter material immersion and discontinuous water flow,the slag filter worked best, and the COD_cr and NH₄⁺-N of the effluent remained under 50mg/L and 2.2 mg/L,meanwhile the removal rate of TP remained 70%;â‘¡on condition of hydraulic loading of 0.80 m³/m².d, the slag filter worked better than that of 1.35 m³/m².d,also the COD_cr and NH₄⁺-N of the effluent remained under 42mg/L and 5 mg/L,the removal rate of the total phosphorus always remained 30%.Dynamic analysis showed that,both Freundlich equation and Langmuir equation could fit isothermal phosphorus absorption properties of furnace slag, river sand and ceramisite perfectly,among which, the top saturated adsorption was ceramisite filter material.Using Michaelis-Menten dynamics to describe the remove rates of COD_cr,NH₄⁺-N and TP,the correlation coefficient were all above 0.95,which showed that the dynamics could fit the remove process of COD_cr,NH₄⁺-N and TP with furnace slag filter material perfectly.Experimental study showed that the vertical flow slug filter could remove COD_cr, NH₄⁺-N and TP effectively, and the running of this prosess is consistent with the farmers'living habits. It has the advantages of small floor area, simplified operation,strong capacity of resisting impact load, stable treatment of overflow water ,which tested and verified the feasibility in the sewage treatment of the northern rural areas .