Study On Enhanced Coagulation Of South-north Water In Zhengzhou And Water Quality Assement Of Danjiang Water

In this paper,the single factor index and the comprehensive pollution index evaluation method are used to evaluate the water quality of Danjiang Water,and compared with other water sources in typical towns along the South-North Water to identify the water quality risks of different water sources.Then it can provide data support for the study of water treatment processes for existing water plants and new water plants along the following multi-water supply.The optimum dosage of coagulant,activated silicic acid and preoxidizer for South-North Water are based on the theory of strengthening coagulation.The effects of pH value on the residual aluminum concentration in the South-North Water are also discussed.Finally,the micro-flocculation and direct filtration pilot test of the South-North Water is carried out to obtain the operating conditions and regular of the process and provide reference for the production of the plant.The main conclusions of this paper are as follows.Single factor evaluation method shows that most of the indicators of Danjiang Water maintained within the class?standard throughout the year.CODMn and TP are belong to class? standard,and TN is1.15mg/L,exceeding the limit of class III standard value of1.0mg/L.The comprehensive evaluation method shows that the quality of Danjiangkou reservoir as a whole class ?.The BOD5 and COD of Danjiang Water perennial belongs to class?standard when from nutrient analysis,and CODMn fluctuates above and below class?standard,but not more than Class II standards.Reservoir nutrition status is poor nutrition status.From comparison of water quality of Danjiang Water with surface water and groundwater in typical cities of South-North Water in Henan,we can see that turbidity,CODMn,total number of bacteria of Danjiang Water are better than groundwater which include Pingdingshan,Zhengzhou,and Xinxiang,and flat with Qihe.But less than underground water.Ammonia nitrogen is superior to other water sources.The total hardness is better than Yuan Yang water and other groundwater sources,and flat with Pingdingshan,Zhengzhou and Hebi.Carry on the enhanced coagulation test for water in South-North Water.The laboratoryexperiment shows that the best dosage of PAFC is 40mg/L when adds coagulant alone,and the removal rate of Turbidity is 88.17%.The best dosage of PAC and activated silicic acid are20mg/L and 5:1 when using activated silicic acid coagulation in laboratory test,and the removal rate of Turbidity is 92%.The removal rate of turbidity is always above 90%,and up to 95.89% when a six-day pilot test is performed with this dosage,and the average removal rate of UV254,NH3-N,NO3-N,CODMn are 41.1%,76.67%,48.21%,51.67% respectively.The indicators above are all have reached the “drinking water health standards” GB5749-2006.The pilot test of three preoxidants of PP,NaClO,ClO2 show that the removal effection of turbidity isn't obvious,just increase by 3%.When the dosage of NaClO is 0.5mg/L,the removal effection of algae is the best,and the removal rate is 78.43%,which above 17.7%than not pre-oxidation.The aluminum of South-North purification water excess in the actual operation.So I design a test that adjust the raw water pH,and it shows that when the pH of raw water is controlled between 7 and 8,the aluminum concentration of the filtered water can be maintained at 0.02 to 0.03 mg/L.And regardless of the first to adjust the pH value of the raw water or the first to add the coagulant,the aluminum concentration of filtered water didn' t have much impact in this pH range.If use PFS as coagulant,it is not necessary to adjust the pH of raw water.Analyse the micro-flocculation and direct filtration process for South-North Water.The orthogonal test shows that the best coagulant is PAC,the optimal dosage of activated silicic acid is 4:1.The pilot test shows that the optimal dosage of PAC is 24 mg/L,and the removal rate of turbidity,CODMn,UV254,NH3-N are 45.0%,59.3%,28.1%,80.0% respectively.The sand filter column recoil cycle is shortened to 9h,which is one-third of conventional process.The horizontal rise rate of the head in the filter column is linear with the filtration time.At the same time the residual aluminum concentration is not exceeded with this PAC dosing.And the dosage is lower 11mg/L than the conventional process.