Study On Emergency Treatment Technology Integration For Drinking Water

In recent years, emergent water pollution caused by chemicals and oil spills,industrial accidents frequently happened, become the main threat to the city drinkingwater safety. China’s urban water supply industry is generallly lack of emergencytreatment capacity, systematic and comprehensive emergent treatment technology todeal with the emergent water pollution incident. This makes the industry an urgent needfor drinking water emergent treatment technology.Powdered activated carbon adsorption, chemical precipitation, chemical redox anddisinfection were chosen to deal with the typical pollutants of different property, andoperating parameters were optimized. Bench-scale experiment was applied to determinethe basic control parameters and then pilot-scale experiment for dynamic simulation.The main results and conclusions are as follows.The adsorption kinetics equation and adsorption isotherm model of powderedactivated carbon were established and the maximum concentrations of pollutantspowdered activated carbon can deal with were obtained based on the investigation ofemergent treatment technology carried in bench and pilot scale experiment. Thecorresponding chemical precipitation technology was chosen to deal with the metal andmetalloid pollutants of different property. The operating parameters including the kindof coagulant, coagulant dose, sodium sulfide dose and pH were established. Chlorite canbe removed greatly using ferrous sulfate, and the maximum removal efficiency at morethan98%arrived with reaction time of5minutes, but it could not be effectivelyremoved with sodium sulfide. Neither sodium sulfide nor ferrous sulfate had goodefficiecy on removing bromate and chlorate. The emergent treatment technology of strengthen disinfection results of freechlorine, chloramines and chlorine dioxide on Escherichia coli, Enterococcus faecalisand Clostridium perfringens showed that the inactivation rate of free chlorine andchloramine decrease while that of chlorine dioxide increases with the rise of pH.Temperature had more significant influence on free chlorine and chlorine dioxidecompared with chloramines. Expressing inactivation rate constant as a function of pHand temperature and applying to the Chick-Watson model, a disinfection model with thetwo parameters of pH and temperature is established with enhanced versatility. Theinactivation rate constant of the disinfectants declined when adding organic matter. Theinactivation rate of E.faecalis decreased with bigger particle size, and increasing thedosage of disinfectant could reduce the impact of particle.The relationship of various factors and the remove effect of powdered activatedcarbon adsorption of2,4-D, chemical precipitation of cadmium and chlorineinactivation of E.faecalis by using the grey analysis method were as follows: powderedactivated carbon dosage> adsorption time> pollutant concentration> CODMn, filteredwater pH> initial concentration of pollutants> coagulant type> coagulant dosage, Ctvalue> disinfection contact time> temperature> disinfectant concentration> pH.BP neural network model was employed to predict the effect of emergencytreatment process. The results showed that the correlation coefficient Rs of powderedactivated carbon, chemical precipitation and the disinfection were0.976,0.996and0.943, respectively, and the RMSE was0.0100,0.0033and0.0050, respectively, whichindicated that the BP neural network model has a good predictive ability of threeemergency treatment processes.Genetic algorithm (GA) had been used to select the optimal parameters ofemergency treatment process based on BP neural network. The results indicated thatunder the condition of powdered activated carbon dosage at67mg/L and adsorptiontime at45min,2,4-D could be reduced to0.027mg/L from the initial concentration of0.67mg/L. Nickel could be decreased to0.018mg/L from the initial concentration of0.9mg/L when pH of filtered water was9.0and the dosage of ferric chloride was4.3mg/L.Integration of emergency treatment technology of drinking water was carried out,and research results were applied in a demonstration project at a waterworks in Tianjin.