Analysis And Optimization Of The Current Situation Of Contaminants Removal In A Groundwater Treatment Plant Rapid Filters In Xi’an

Based on a practical project in Xi’an to optimize the operation of a groundwater treatment plant,this research made clear the status of water plant operation and proposed optimization scheme by analyzing and evaluating the actual operation of filters in case water plant.In this study,a pilot-scale filter system was utilized to evaluate the performance of iron(Fe²⁺),manganese(Mn²⁺),and ammonium（NH₄⁺-N）removal via the naturally quartz filter media and activated carbon,and then the optimization of filter media was performed.The possibility of carbon filter material being converted into biological activated carbon was analyzed.Meanwhile,the application of catalytic oxidation to removal of NH₄⁺-N and Mn²⁺technique in the transformation of production filter was investigated.An effective and reliable operating system was established though this research for the quartz sand and activated carbon filter in case treatment facility.The following are the main research conclusions:（1）The catalytic activity for Mn²⁺and NH₄⁺-N removal of the oxide film naturally formed on the surface of the filter material in the quartz sand filter tank in a groundwater treatment plant is poor.In the pilot-scale filter system,the removal rate of Fe²⁺,Mn²⁺and NH₄⁺-N at low concentration can remove completely after 3 days’optimization.（2）Three kinds of pre-oxidation methods（aeration oxygenation,chlorination peroxidation,potassium permanganate peroxidation）can resist the risk of excessive Fe²⁺and Mn²⁺to a certain extent.However,these pre-oxidation methods exhibited little impact on the NH₄⁺-N removal.For the sand filter,the period and intensity of backwash make no difference to the removal of contaminants.（3）When the in-situ preparation of active oxide film is carried out in the quartz sand filter tank of water plant,the rapid preparation of active oxide film can be completed under the appropriate backwash conditions and the film is attached for about7 days.After the in-situ modification in the quartz sand filter tank,the ammonium and manganese removal efficiency increased from 28%to 90%and from 50%to 80%,respectively,when the influent NH₄⁺-N and Mn²⁺concentration were 0.3 mg/L.The characterization analysis of the filter media showed that the morphology and structure of the modified filter media have changed.XRD analysis results showed that the modified filter media appeared a new peak,which proved that the active filter media was formed.（4）The activated carbon exhibited high removal efficiency on Fe²⁺,Mn²⁺and NH₄⁺-N,but the performance on phosphorus and organic matter was less than satisfactory.The capacity of activated carbon to eliminate contaminants by adsorption was reduced compared with that of the original filter material.In addition,compared with the current activated carbon material,the original carbon is about 3-4 times that of the activated carbon filter material.However,the inactivation experiment shows that the removal of pollutants in carbon filter mainly depends on biological action at present,so the filter material of carbon filter does not need to be replaced temporarily.（5）Compared with the filtration rate of 8 and 10m/h,under the operating conditions with a filtration rate of 6m/h,the removal efficiency for Fe²⁺,Mn²⁺and NH₄⁺-N of activated carbon was slightly much better.The period and intensity of backwash make no difference to the removal of contaminants in carbon filter.（6）Nutrients,light and hydraulic residence time all have an effect on the amount of algae in the carbon filter,and the addition of shading measures above the carbon filter is conducive to the inhibition of algae reproduction.After the addition of shading measures,the number of algae in the carbon filter decreased from 1.2 million/L to250,000/L,and the addition of shading measures had no effect on the removal of pollutants in the carbon filter.