Set Up And Applied Research Of Water Quality Model Based On The Chlorine Residual Decay

Urban water supply system is mainly used to provide safe and reliable water,including water quantity and water quality.The guarantee of water quantity is to provide enough water for users;the guarantee of water quality is to provide qualified water for users,and disinfection is the key part of ensuring water quality.Study on the attenuation of residual chlorine in the network and set up the chlorine decay model of water quality have great significance to ensure water quality.In this paper,a detailed survey of existing water supply network on the basis of water quality is conducted.we use the finished water of a waterworks as raw water with chloramine as a disinfectant.The jar experiment is conducted in the laboratory.The effects of organic matters,initial concentration of Chlorine,pH,temperature,NO₂^-on the bulk decay of residual chlorine are studied in the experiment.According to the water quality survey of existing network,a water supply pipe network in the laboratory simulation system is established.The water of a waterworks as the research object,the effects of initial chlorine concentration,pH,flow rate,pipe material and pipe diameter on the decay of residual chlorine are studied.With water supply scope of the second water plant in the eastern region of Fengxian as the main study subject,existing model is improved and residual chlorine decay water quality model is set up on the basis of existing hydraulic model,combining with experiment,literature and other related content.Multistage chlorine scheme is optimized using residual chlorine decay water quality model.The results are as follows:Residual chlorine decay rate increases with the concentration of the organic matter;When the concentration of organic matter is low,water residual chlorine of different organic matter concentration is larger;when the high concentration of organic matter in water,residual chlorine concentration difference of different organic matter;at the same time,initial chlorine concentration of different chlorine consumption is different;the initial chlorine concentration of large consumption per unit time of residual chlorine is large;when pH increases from 6.50 to 8.50,the residual chlorine decay curve becomes more and more slowly;and the rate of residual chlorine decay becomes more and more slowly;in the first 20 hours,water samples at different temperatures of chlorine consumption is basically the same;but with the extension of time,in the temperature range from 4℃³0℃,increase with the increase of chlorine consumption temperature increases;within 168 hours,the higher concentration of NO₂^-in water,residual chlorine decay rate is faster,the total residual chlorine consumption amount is large.On the basis of the analysis of the effects by various factors,a decay model of residual chlorine in bulk water is developed and validated and the model shows good predicative results.when the flow rate increases,the residual chlorine consumption rate also increases;flow rate increase later also easy to make the biofilm attached on the pipe wall and sediment loss,resulting in an increase in water turbidity;residual chlorine reaction biofilm off with water,accelerate the chlorine consumption;with the increase of the initial concentration of chlorine,chlorine decay rate increases;when the water retention of 24 h in the pipeline,no matter how initial chlorine concentration,residual chlorine in water are stable at a low level;when the water pipe network of p H increases,the residual chlorine consumption rate decreases;When the water pipe network pH is relatively low,water strong corrosive,easy to pipe wall corrosion;wall corrosion products may cause turbidity rises into the water;the smaller the pipe is,the more influence the interior wall of the pipe puts on the quality of water,for the contact ratio between water and pipe wall will increase in smaller pipes.Considering the effect of Reynolds number,initial chlorine concentration and pH on chlorine wall decay coefficients,a chlorine wall decay coefficient model is developed.The best chlorine point in the pipe network system is found out through the model of chlorine point location optimization,result shows that Pingan pump station is the optimal solution which is consistent with the present situation.After chlorine quantity optimization,the new chlorine water solution is put forward,the chlorine dosage is 0.85 mg/L in water works and 0.2 mg/L in Pingan pump station,which makes the sum of chlorine content decrease 39.83% to improve the efficiency of chlorination and save the cost of production.