Assessment Of Water Quality Risk And Study On Emergent Treatment Method

Water supply system is an important city facility and plays a key role in citydevelopment and social stability?Recently,due to environment changes?industry andagriculture production and people'S life?the quality of water environment becomesworse in our country?But the requirements of drinking water quality becomecontinuously more rigorous Meanwhile?with the persistent pollution not beingcontrolled?water pollution accidents?represented by traffic accidents?industrialaccidents and illegal discharge?occur more and more frequently?So new-dangers axebrought to water supply safetyPresently,studies on water safety axe carried out in many cities in our country,including potential t11]reat analysis?treating measures study and emergency schemestudy?However,it is essential to developing specific water safety studies as thepollution situations?water treatlllent processes and other conditions are different Bytaking the water supply system of a certain city in northwest?the risk assessment ofwater quality,water quality changes analysis and prediction?potential pollution sourcesand characteristics analysis?and emergency treatment technologies are studied in thisPaper1)The assessmem model of source water quality based on fuzzy theory andprincipal componentIn order to solve the problems oftraditional assessmem models in factor selection?weights assigning and results analysis?a fuzzy synthesized assessment model based onprincipal component analysis is proposed?which sifts factors by dimension reductionprinciple and characterizes the different quality level and existence of over-prooffactors based on level characteristic value?The results show-that w-hen the levelcharacteristic value is more than two?it indicates that there are over-proof factors?nomatter what the assessment result is?and as the level characteristic value is bigger,the quality is worse By taking the water quality indices which are analyzed by the modelas assessment factors?the level characteristic value can reflect existence of over-prooffactors more accurately?2)Analysis of source water quality changesThe characteristics of main indices in surface water plants and ground waterplants are studied by Spearman rank related coefficient method and seasonal Kendalmethod The results shove-that the CODMn?COD~?and TP in surface water plantspresent a rising tendency,which indicates the existence of organic pollution risk,algaepollution risk and disinfection by-products risk In ground water plants?the naturalchemical characteristics don't chmage worse?microbe indices(total bacteria andcoliform group)continue to be lower,nutrient composition is stability and organicpollution risk is relatively small?but Mmaganese and Nitrite pollution risk is relativelyhigh Moreover,an the condition of indistinctive Seasonal VaJdation?relatively smallmnount of missed measure and singular values?and only needing qualitative evaluation?the Spearman rank related coefficient method show-s the same results with the seasonalKendal method and better application foreground?because of easy calculation and lowrequirement to data quantity?3)The chaotic prediction model of source water quality based on LyapunovexponentBased on chaotic theory and existing research results in other fields?theprediction model of source water quality is established and the application effects ofthis model are discussed as well The results show-that rave-water quality time seriesposses chaotic characteristics?it is possible to predict short-term variation?and theaccuracy ofmodel prediction is verified and the average error is less than 10?4)Analysis of pollution risk sources in water source areasAccording to field investigation and data collection?the types and characteristicsof potential pollution sources in case city water source areas are studied in detail Theresults shove-that sudden pollution sources including release source?industrial source?area source?internal source and natural disaster source?are the main risks in surfacewater protection areas?which take instantaneous discharge of large amounts ofpollutants as characteristics and can induce several pollution types?such as petroleumpollution?nitrogen and phosphorus pollution?heavy metal pollution(Cd?Or)Moreover,conventional pollution sources including industrial source?recharge source?agricultural production sourc?resident life sourc mad solid wastes source?are the mainrisks in groundwater protection areas?which take accumulation of pollution as characteristics and can induce several pollution types?such as organic pollution?nitrogen element pollution?especially ammonia nitrogen pollution5)Analysis oftreatment capability of surface water plantsBased on typical potential pollutaats?such as orgafic compounds?totalphosphorus and heavy metal(Cd?Cr)?the treatment capability of surface water plantsis discussed The results show that the average removal rate of CODMn is about 38 3??which is relatively lOW,but by enhancing coagulation?it can meet requirements at thepresent quality condition The removal rate of TP is from 60?to 90??which isrelatively high?and it means less security risk The maximum load of hexavalentchromium and divalent cadmium which the conventional process can treat?are0 1 50mg?L and O 025m/l?it mean large security risk in emergent treatment6)Proposing the construction scheme of emergent treatment system in case cityIn viev~-of difl~rent risk and existing emergency condition in surface water plantsand ground water plants?the emergent treatment system is studied in detail based onexperimental results?which takes dosing system of powdered activated carbon andchemicals as the key in surface water plants?and the process of potassiumpermanganate oxidation and sand filtration in ground water plants The results show-that powdered activated carbon adsorption and chemical precipitation are the commonemergent treatment methods to sudden pollution incidents The strategic pass movedforward can be realized?which can reduce pollution load and influence of pollutionincidents to plants operation?when the emergent treatment system is constructed at theriver junction management station of the main water supply source Meanwhile?theprocess of potassium permanganate oxidation and sand filtration presents the stableoperation effect at the condition of Mn O 7m?L and ammonia-nitrogen 1 lmg?L?which means the process proposed in the paper can meet the emergent treatmentrequirements of high manganese and high ammonia-nitrogen risk in case city?...