Study On Application Of SWB System In Treating Cows Farm Wastewater

Animal husbandry is rapid expanding as state economic developing and living standards of residents upturning,and results in serious environmental pollution.Animal husbandry has become primary pollution source in rural area in Chongqing.It not only endangers animals' and human health,but also has a strong negative impact on development of rural economics.Animal husbandry pollution improvement has become one of pressing tasks in present.Animal husbandry wastewater is difficult to control for various reasons.Apply traditional sewage sludge treatment plant to animal husbandry wastewater treatment mechanically is not a appropriate way.It's essential to study a technical that is low investment,low running cost, effective treatment and convenient management to treat animal husbandry wastewater.According to topography and climate in Chongqing,a simple anaerobic pool(SAP),wavy flow constructed terrace wetland(WFCTW)and biological pond(BP)system apply to treat dispersive medium and small sized stock farm wastewater was studied.Suspended substance(SS),chemical oxygen demand(COD),total nitrogen(TN),ammonia nitrogen(NH₄⁺-N)and total phosphorus(TP)removal efficiencies and mechanisms in each processing unit were studied and characteristics of SWB system were analyze in this paper,it can reach following conclusions:(1)Although the wastewater at the influent of the SWB system is high concentration cows farm composite waste,treatment showed high mean removal efficiencies of 91%,89%,79%,62% and 88%for SS,COD,TN,NH₄⁺ -N and TP respectively.(2)In the SWB system,SS are physically separated from the wastewater by filtration and sedimentation.The organic content of the trapped solids is then gradually decomposed,while the inorganic content is integrated and forms part of macrophytes bed matrix.Organic matter in the wastewater,represented by COD,is removed mainly through aerobic biological decomposition and anaerobic biological decomposition by microorganisms growing in the SAP flexible filler and WFCTW matrix.TN is changed into NH₄⁺ -N by ammonification bacteria in SAP,and then NH₄⁺ -N is removed mainly through changing into N₂ and N₂O by nitrifying bacteria and denitrifying bacteria.Sorption to storm is the main mechanism of phosphorus removal.Heavy metal ions can be uptook by macrophytes,so that harvesting macrophytes can remove heavy metals. (3)Every processing unit of the SWB system has a very good complementary between each other.(4)Cyperus alternifolius Linn and Canna indica Linn are feasible macrophytes in constructed wetland.In the SWB system,the four beds filled with different storms and a comparison was made for the P and N removal efficiency between limestone bed matrix and mixed storms bed matrix.The result showed pulverized fuel ash mixed with limestone can improve P and N removal efficiency.(5)The SWB system along with cost-benefit ratio(cost value/economic benefit)of 1:1.2,and its environmental and economic benefit is greatly prominent.So it has a certain promotable and applied prospects.This study of innovation in the following three points:(1)The SWB system was constructed on the hill.So that it improve dissolved oxygen consistency by waterfall reoxygenation without electric energy.The relationship between height and flowrate of waterfall and waterfall reoxygenation was studied.(2)Wastewater is drains through the matrix from bottom to top and from top to bottom repeatedly by setting up clapboards.So WFCTW is equipped with strongpoint of surface flow constructed wetland and horizontal subsurface flow constructed wetland.It can improve pollutant removal efficiency by enhancing the interactions between pollutants in the wastewater and microorganisms attached on the roots of macrophytes and surfaces of storms and increasing the availability of oxygen by wavy surface reoxygenation.(3)DO situation in WFCTW was studied.The result showed DO in the surface,middle and bottom of bed matrix are different.So pollutants are good removed by various biochemical reactions when the sewage flowed in bed and repeated experience of Oxidation/reduction micro-environment.