Research On Improvement Of Water Chemical-stability Of Drinking Water Distribution System By Lime And Carbon Dioxide Process In S City

The raw water in S city has the characteristics of low alkalinity,low hardness and strong corrosion,and the water chemical-stability is poor.For the water chemicalstability of the the treated water by conventional water purification process is still poor,it will cause corrosion of the inner wall of the pipe network entering the drinking water distribution system,which results in water quality problems such as "yellow water".Lime and carbon dioxide process is suitable for the treatment of water quality in low alkalinity and low hardness,but its key technological parameters and application effect in drinking water distribution system in S city are still to be studied.This topic is based on the lime and carbon dioxide process,to investigate the improvement effect of this process on th water chemical-stability in S city,to study and evaluate the parameters and effects of the lime and carbon dioxide process,hoping to improve the water chemical-stability of drinking water distribution system in S city and providing data support and reference for similar cities in the future.By studying the water quality characteristics of drinking water distribution system in S city,the total alkalinity,calcium hardness and CCPP showed that the water in S city was corrosive all the year round and the water chemical-stability was poor.The water chemical-stability of drinking water distribution system in S city was closely related to the corrosion and scaling on the inner wall of the pipe network.The worse the water chemical-stability is,the more corrosive the water quality is,the more stratified nodular scale will be produced.In the experiment on the change of water chemical-stability,the reliability of the total alkalinity and calcium hardness of the identification indexes of water chemical-stability was verified by the scaling and corrosion of water,which provided a foundation for the subsequent research on the improvement of the water chemical-stability of drinking water distribution system in S city.Through small-scale experiments,the main parameters of the lime and carbon dioxide process section were optimized.The results showed that when the total alkalinity of the influent was 29.2?31.7 mg/L CaCO₃,the calcium hardness was 27.0?35.7 mg/L CaCO₃,and the CCPP was-7.6?-6.3 mg/L CaCO₃,adding lime first and then adding carbon dioxide was the best order.Under this optimal dosage order,the experiment was conducted according to the optimal dosage quantity of lime 60 mg/L and carbon dioxide 40 mg/L,and the total alkalinity,calcium hardness and CCPP of the treated water could reach 86.0,66.0 and 2.3 mg/L CaCO₃,the water chemical-stability would be significantly improved,and other water quality indicators met the requirements of drinking water hygiene standard in China.This process was combined with the conventional water treatment process in the pilot test,and further application research on the water chemical-stability of drinking water distribution system in S city was studied.The results showed that after 24 days of stable operation in the pilot plant,the total alkalinity,calcium hardness and CCPP of the treated water could reach 70.3,60.6 and-8.7 mg/L CaCO₃,respectively,indicating the water chemical-stability of the treated water was improved.In the drinking water distribution system experiment,the total alkalinity,calcium hardness and CCPP could reach 67.4,74.9 and-7.9 mg/L CaCO₃.Although the water chemicalstability of the drinking water distribution system was lower than that of the treated water,it's better than the water chemical-stability of the drinking water distribution system when no application research was carried out.After adding the lime and carbon dioxide process,the construction cost was about 1.318 million yuan,and the cost of medicine was 0.247 yuan/m³.