Study On The Technology Of Wastewater Reusing Safely In Beijiang Waterplant

The research object of this study is Beijiang Water Plant of Foshan, Guangdong Province, toassess production wastewater reuse water risk through analysis of level change of productionwastewater Beijiang Water Plant under different raw water conditions; to assess productionwastewater reuse water quality risk through tests of representative organic matter, metal ions,acrylamide and disinfection byproducts indicators; to analyze effect on water quality byreusing production wastewater under different raw water conditions; to tracking water qualityunder long-term use of production wastewater return water; to analyze production processadjustment of Beijiang Water Plant after resuing wastewater and operation costs of system ofreusing production wastewater.Studies indicate that filter backwash water is of high content and quality, very low content ofammonia nitrogen, dissolved organic matter and metal, with low risk of reusing. Direct reuseof backwash water can improve water coagulation performance and save consumption ofchlorine, but because of much suspended solids it must be chlorine disinfected, this may causeoverproof of chloroform of finish water.Quality of concentrated supernatant water greatly changes with seasons, maximum turbidityin high turbidity period will go up to36000NTU, which has great impact on conventionalwater treatment processes; in August ammonia nitrogen will be up to1.91mg/L, causingincrease consumption of chlorine. The highest content of dissolved Manganese was1.88mg/L,which may cause overproof of Manganese.Dewatering leachate is of poor quality. Its ammonia nitrogen is up to8.27mg/L, COD_Mn upto21.3mg/L, dissolved Manganese content up to6.36mg/L, acrylamide up to10.4ug/L.Because of its low quality, high safety risk and small content, it is not suggested to reusedewatering leachate.Through studies we can see that special process way can be used for special water quality. Forexample, in high turbidity period, Beijiang Water Plant overcomes adverse effects of highturbidity and large amount of reclaimed water through coagulation method of largelyenhanced dosing of polymerization aluminum chloride （PAC）, making water quality is not affected, and also realize zero discharge of waste water in high turbidity period.While wastewater is reused treatment plant processes should be adjusted accordingly: strictlycontrol production waste water reflux ratio, highly multiple levels of dilution of contaminantsin wastewater; for water plant which directly reuses filter backwash water, reuse times andchlorine disinfection time should be staggered, to minimize formation of chloroform andother disinfection by-products.Economic analysis showed that, Beijiang Water Plant, the daily water supply volume ofabout280000cubic meters, theoretical running costs of which production wastewater reusesystem is RMB640,000per year. Through saving water resources fee, price regulation fundcost and partial cost recovery barrel cleaning, the actual annual operating cost isRMB270,000, with an cost increase3cents per ton, which has economic advantageespecially in places of high cost of water resources fee and water transportation of waterreuse process.