Application Of Polyurethane Filler Biofilter To Treat Micro-polluted Drinking Wate

In the typical arid and water-deficient areas in western my country,problems such as resource-based water shortage and water-quality water shortage are common.Residents in the vast rural areas generally drink rivers,streams,pits,ponds,mountain springs and groundwater that are simply treated.The water quality risks are high.Groundwater is at high risk of being polluted by iron,manganese and ammonia nitrogen,and surface water has problems of high turbidity and high algae in summer and autumn and low temperature and low turbidity in winter and spring.Conventional water treatment processes mainly remove microorganisms and turbidity in water bodies,and it is difficult to effectively remove dissolved micropollutants.In this study,the biological filter with polyurethane as the filler was used as the main body of the experiment.The biological filter was started with membrane hanging,and its operation under different filtration rates,filter material thicknesses and concentrations of influent organic matter and NH₄⁺-N was studied;the degradation kinetic equation was established for the removal of organic matter and NH₄⁺-N from the biological filter;The adsorption characteristics of polyurethane as filler were studied;the recovery ability of the biofilter after shutdown was investigated.The subject originates from the national key R&D program"Demonstration of Integrated Technology and Application of Rural Water Supply and Drainage in Typical Water-deficient Areas in Western China"-"Research and Demonstration of Key Technologies for Rural Drinking Water and Sewage Treatment in Ningxia Hetao Area（2016YFC0400705）"project of micro-pollution organic matter and ammonia nitrogen Research related content of processing technology.The main research results are:（1）The experiment adopts the method of natural film hanging,and starts the biofilter of polyurethane filler.It is observed that the color of the carrier gradually becomes darker,and the biofilm attached to the carrier gradually increases.After 30 days of reaction,the CODMn removal rate was stable at about 45%,the effluent concentration was stable below 3mg/L,and the removal rate of NH₄⁺-N reached more than 80%and remained stable.After that,the removal rate of COD_Mnand NH₄⁺-N stabilized at about 45%and 85%and basically did not change,which indicated that the membrane start-up of the reactor had been successful.（2）The removal effect of the biological filter bed with different filtration rates and filter material thicknesses was investigated:the lower the filtration rate and the filter material thickness,the better the treatment effect.When the filtration rate was 0.1m/h and the filter material thickness was 1m,the treatment effect was the best.Well,the average effluent concentration of COD_Mn is 2.61 mg/L,NH₄⁺-N is 0.05mg/L,NO₂^--N is below 0.01mg/L,NO₃^--N has a small amount of removal,TFe is 0.04mg/L,Mn²⁺is 0.03mg/L.However,considering the comprehensive treatment water volume factors,it is considered that the optimal filtration rate of the biological filter bed should be 0.4m/h.At this time,the average effluent concentration of COD_Mn is 2.76 mg/L,NH₄⁺-N is 0.15mg/L,NO₂^--N is 0.02 mg/L,NO₃^--N is basically consistent with the influent water,TFe is 0.08mg/L,Mn²⁺is 0.03mg/L.The effluent meets the sanitary standards for drinking water.（3）The removal of various pollutants by the biological filter was studied when the influent concentrations of ammonia nitrogen and organic matter were different:when the influent with high ammonia nitrogen concentration（2mg/L）,the average COD_Mnconcentration in the effluent was 3.64 mg/L,and the effluent NH₄⁺-N concentration averaged0.66 mg/L.When the influent with high organic matter concentration（8mg/L）,the average concentration of COD_Mn in the effluent is 3.68mg/L,and the NH₄⁺-N is 0.51mg/L.When high ammonia nitrogen or high organic matter enters the water,the effluent cannot meet the"Drinking Water Sanitation Standard".（4）The kinetic model of COD_Mn and NH₄⁺-N removal by biofilter was established,and the kinetic equations were obtained by experimental linear fitting,S＿e=S＿0×e^（-0.242t）,S＿e=S＿0×e^（-0.486t）.The kinetic equations of COD_Mn and NH₄⁺-N removal by biofilter were verified by experiments.After calculation,the experimental detection values of COD_Mnand NH₄⁺-N are basically consistent with the calculated values of the kinetic model,indicating that the kinetic equation can basically reflect the removal law of COD_Mn and NH₄⁺-N.（5）The adsorption performance of filler（polyurethane）was studied,and the isothermal adsorption model and adsorption kinetic model of polyurethane for various pollutants were established.The adsorption process of polyurethane for organic matter,NO₃^--N and TFe is more in line with the Freundlich isotherm adsorption model and pseudo-first-order adsorption kinetic model,the adsorption process of NH₄⁺-N is more in line with the Langmuir model,and the adsorption process of Mn²⁺The Freundlich model and Langmuir model All the models are in good agreement with the pseudo-second-order kinetic model for NH₄⁺-N and Mn²⁺.When the biological filter is running,the adsorption capacity of polyurethane to organic matter,NH₄⁺-N,NO₃^--N,TFe and Mn²⁺is about 55mg/kg,90mg/kg,55mg/kg,25mg/kg and30mg/kg.The adsorption process is reversible and can be desorbed and regenerated..（6）The stability performance of the polyurethane-filled biofilter,that is,the recovery ability after stopping operation:the recovery period of the polyurethane-filled biofilter is shorter,and it takes four days when the biofilter is out of operation for five to ten days.The time can be restored to the normal operation state,and the removal effect of Mn²⁺is slow to recover at this time;when the operation is stopped for fifteen days,it takes five to six days to restore the previous treatment effect.Fifteen days after the operation was stopped,the removal of COD_Mn,NH₄⁺-N,TFe and Mn²⁺was affected to varying degrees at the beginning of the re-injection,and the removal rate decreased greatly.After that,the removal capacity gradually decreased due to the continued operation of the biological filter.The recovery further indicates that the biological filter treatment and removal of wastewater is mainly completed by the degradation of biofilms.