Development And Application Of Residual Chlorine Replenishment Device In Secondary Water Supply System

The widespread use of secondary water supply facilities has effectively eased the contradiction between water supply and water use in high-rise buildings,and has become an important part of the urban water supply system.However,secondary pollution is extremely likely to occur at the secondary water supply facility,which has a potential threat to users’ drinking water safety.The deterioration of the quality of the secondary water supply mainly includes the serious loss of residual chlorine at the end of the water supply system,secondary pollution in the water tank,and excessive hydraulic retention time.This research uses a combination of theoretical research and experimental verification,with sodium hypochlorite solution as the disinfectant,combined with the characteristics of the secondary water supply system,a chlorine water disinfection system for the secondary water supply tank based on incremental PID control was constructed.Discrete control realizes the periodic feedback adjustment of the dosage of sodium hypochlorite,and finally achieves the purpose of stable control of residual chlorine in water.The system adopts the multi-channel feeding method,taking the water inlet of the water tank as the main feeding point,and adding chlorine in a proportional way according to the amount of water intake;using the outlet of the water tank as the auxiliary feeding point,when the water at the water outlet When the chlorine concentration is low,add chlorine according to fuzzy control.In the process of adding chlorine,the system continuously detects and analyzes the residual chlorine concentration at the outlet of the water tank,and periodically adjusts the amount of added chlorine.This system mainly solves the water quality problems commonly existing in the current secondary water supply system,especially the problem of insufficient free residual chlorine in the water at the end of the water supply.The research and development of the secondary water supply residual chlorine supplement device and the supporting system applied to the secondary water supply facility in a city in northwest China,respectively,to conduct chlorine disinfection and residual chlorine supplement test test,so as to control the stability of the system operation and residual chlorine control The effect is optimized and perfected.The main research results and conclusions are as follows:(1)In the process of chlorination and disinfection,the residual chlorine concentration should be used as the main control indicator to ensure that the residual chlorine of the user’s tap water basically meets the standard.Taking turbidity as a general control index,it is required that the turbidity of the water after chlorination is not abnormal.(2)The user’s water consumption pattern is the main cause of unstable system operation(abrupt change in residual chlorine concentration).Analyzing the user’s water usage pattern and formulating the corresponding dosing mode according to its water usage characteristics can enhance the stability of the system operation.(3)After optimizing the effect of water on the effect of chlorination,the system has strong robustness,and the system operation stability has been significantly improved.The concentration of residual chlorine in the water at the outlet of the water tank is controlled at about 0.13 mg/L,and the compliance rate of residual chlorine in the tap water of the user is above 95%.(4)Using the water replenishment volume of the water tank in a dosing cycle as the basis for the dosing cycle control can speed up the system response speed.Relevant optimization for the control of the dosing cycle can shorten the feedback adjustment cycle and reduce the inertness of the system response.Control the concentration of residual chlorine in the water at the outlet of the water tank to about 0.10 mg/L,and the compliance rate of residual chlorine in the tap water of the user is above 96%.(5)After optimizing the system operation stability and residual chlorine control,the residual chlorine supplement device based on the system can be applied to various secondary water supply systems with large changes in water quality and quantity.It has a significant improvement effect on the damaged water quality in the end of the current urban water supply network,and can provide a certain water quality guarantee effect for the user’s tap water.