Study On Water Quality Warning Model Of Surface Water Source For The City Water Works

With the continuous development of the economy in the huai river basin, sewagedischarge and agricultural non-point source pollution become more and more serious.The period of pollution is prolonged from days to months and has the features ofheavy pollution, it mainly shows the overweighted organic and ammonia nitrogenwhich give a big challenge to the treatment of the drinking water in the city of huairiver water source. Certain city is located in the middle reaches of huai river and thewater supply of this city mainly depend on huai river. Because the economic level stilllags behind, it is difficult for old waterworks to have a large scale reform on deeptreatment. Drinking water safety problem is very serious.In order to supply the data to the early warning emergency plan of the city, thisarticle summarized the study history and development trend of water quality earlywarning model of water source at home and abroad;Considering the features of heavypollution in the Huai river,the possible of getting data,practical applicability andmaintenance of model and so on,the author selected WASP7.41as the water qualityearly warning model of water source;On the basis of the statistics and analysis to thecollection and the survey and monitoring of data, the author identified the water qulitywarning index and alarm value at the water intakes of water works,parameter of earlywarning model and the upstream early warning monitoring section,and then adoptedthe practical monitoring data to correct the parameter and verify the model;the authorapplied WASP7.41to predict the alarm values of water quality index at the upstreamearly warning monitoring section,the concentration of them at the water intakes andthe emergency response time for the four water works.The main contents and conclusions of this research are as following：（1）By reading the literature,we known the research situation of water qulity earlywarning of water source including the monitoring and model.（2）According to the feature of typical water quality model and the practicalconditions of the river,we selected WASP7.41as the water qulity early warning modelof the city.（3）By collecting the data and practical survey and monitoring,we concluded thewater environmental situation and pollution load and seasonal hydrological conditionof the river（river terrain，flow process）.（4）We analysed the water qulity of history and status of the river and identified theCOD_Mnand NH₃-N as the main water qulity index of early warning,and establishedthe related equation between COD_Mn,COD_crand BOD₅.We adopted the water qulitymonitoring data from2007-2009to establish the linear regression equation betweenCOD_Mn,COD_crand BOD₅: BOD₅=0.205COD_cr-2.814, BOD₅=1.444COD_Mn-3.440,the correlation is0.908and0.968respectively.We also calculated the values ofaverage relative error with the water quality monitoring data of2010,and the result shown that the regression equation could be used in the transform of data in the earlywarning model.（5）According to the hydrological,terrain,meteorological and pollutant dischargedata of collection, we identified the related hydraulic and water qulity parameter ofmodel and analysed the sensitivity of water qulity parameter and assessed the result ofcalibration of it.The result shown that: CBOD deoxygention rate at20℃was0.21d^-1; CBODdeoxygention temperature coefficient was1.07; CBOD degradation half saturationconstant was0.25mg/L; Nitrification rate at20℃was0.1d^-1; Nitrification ratetemperature coefficient was1.07; Nitrification rate half saturation constant was0.5mg/L; Minimum Temperature for Nitrification Reaction was10℃; ReaerationTemperature Correction was1.03; Minimum Reaeration Rate was0.2d^-1; GlobalReaeration Rate Constant was0.8d^-1; Sediment Oxygen Demand was0.3g/m2/day.The parameter that had great infuluence to CBOD in turn was T、KBOD、Q、K2、SOD、KNOD,and KBODand KNODwere positive sensitivity,others were negative.The parameter that had great infuluence to NH₃-Nin turn was T、KNOD、Q、K2、KBOD、SOD，and KBODand SOD were positive sensitivity,others were negative.The globale errors of the result of simulation and monitoring data of COD_MnandNH₃-N of water works was small, the value of PBISA could respectively be controlledbetween5%and22%that shown the identified parameters of COD_Mnand NH₃-N inmodel was reasonable.（6）We adopted the practical monitoring data to test and evaluate the establishedwater qulity based on WASP7.41.The result shown that the globale errors of thepredicted result of COD_Mnand NH₃-N was small and PBISA could be controlled in30%.（7）Through the statistical analysis of data of collection, we identified the alert valueof water quality index at water intakes of water works and early warning monitoringsection.In dry season, NH₃-N and COD_Mnof the first water works were1.60mg/L and4.76mg/L; NH₃-N and COD_Mnof the second water works were1.00mg/L and4.35mg/L; NH₃-N and COD_Mnof the third water works were1.72mg/L and4.76mg/Lï¼›NH₃-N and COD_Mnof the fourth water works were1.50mg/L and4.84mg/Lï¼›In wetseason, NH₃-N and COD_Mnof the first water works were1.50mg/L and5.17mg/L;NH₃-N and COD_Mnof the second water works were1.00mg/L and4.29mg/L; NH₃-Nand COD_Mnof the third water works were0.75mg/L and5.26mg/L; NH₃-N andCOD_Mnof the fourth water works were1.75mg/L and5.26mg/L; The early warningmonitoring section was set at upstream intet.（8）We applied WASP7.41to predict the alarm value of water quality index of early warning at early warning section and calculated the emergency response time.In dry season, NH₃-N and COD_Mnof the first water works were1.8mg/L and5.051mg/L; NH₃-N and COD_Mnof the second water works were0.8mg/L and4.46mg/L; NH₃-N and COD_Mnof the third water works were0.8mg/L and5.051mg/Lï¼›NH₃-N and COD_Mnof the fourth water works were1.25mg/L and4.737mg/Lï¼›In wetseason, NH₃-N and COD_Mnof the first water works were1.6mg/L and5.130mg/LNH₃-N and COD_Mnof the second water works were0.7mg/L and4.42mg/L; NH₃-Nand COD_Mnof the third water works were0.5mg/L and4.894mg/Lï¼›NH₃-N andCOD_Mnof the fourth water works were0.7mg/L and5.522mg/L;It was0.453d for pollutants to arrive at water intakes of the second water worksin dry season and0.183d in wet season; it was1.073d for pollutants to arrive atwater intakes of the fourth water works in dry season and0.436d in wet season; itwas1.196d for pollutants to arrive at water intakes of the third water works in dryseason and0.485d in wet season; it was1.301d for pollutants to arrive at waterintakes of the first water works in dry season and0.530d in wet season.