Research On Applicability Of Yangtze River Raw Water By Coagulation Ultrafiltration Processes

Under the multiple pressure of increasing micro-pollution characteristics of Yangtze River,strict hygiene standards for drinking water and the demand of people along the river for high-quality drinking water,numerous coagulation-sedimentation-filtration-disinfection-oriented drinking water plant are facing the technical problems of upgrading.Currently,the water plants in Yangtze River Basin often adopt to ozone bioactive charcoal and ultrafiltration membrane combination process as depth processing technology.In terms of ultrafiltration membrane combination process,the combination of coagulation and ultrafiltration,not only can play their respective advantages,but also can ensure the water quality and biological safety,in fewer dosages of chemicals,is a relatively clean process,which has a broad application prospects in water plant reconstruction,expansion and new construction.Based on the study of the connection among coagulant,coagulation conditions and ultrafiltration membrane fouling,this paper carryed out continuous experiment of Yangtze River Water by short coagulation-ultrafiltration process with low pharmacy.Meanwhile,using pre-treatment means of potassium permanganate and powdered activated carbonto optimize coagulation-ultrafiltration process.In addition,evaluation of LJ coagulation-ultrafiltration water plant was also introduced in the thesis.We hope these studies can provide a new method for the upgrading and expansion of the water plant.Firstly,these factors,such as flocculant type,the amount of flocculant,flocculation time and water temperature were taken into consideration of these experiment in order to study membrane fouling.and investigated the effects of flocculant type,dosage and flocculation time on floc particle size and fractal dimension.It was found that polyaluminum chloride was superior to polyferric sulfate,large doses of flocculant and long flocculation time are not conducive to membrane fouling control and a certain correlation among flocs' particle size,floc fractal dimension and membrane fouling.The effect of temperature on membrane fouling was significant.Then,using pretreatment of potassium permanganate and powdered activated carbon optimized coagulation-ultrafiltration process and carryed out the experiment containing coagulation-ultrafiltration KMnO4+coagulation-ultrafiltration,PAC+coagulation-ultrafiltration.The results showed that all of these processes have a high removal of turbidity.and the removal rate is up to 99% or more.During the period of normal dosage,the removal rates of CODMn were 36.5%,43.4% and 43.8%,respectively.Potassium permanganate and powdered activated carbon can increase the removal rate of 6.9% and 7.3%.When it comes to reduction of dosage,the removal rates of CODMn were 33.6%,42.4% and 41.4%.Potassium permanganate and powdered activated carbon can increase the removal rate of 6.9% and 7.3%.Dosing reduction do not obviously affect the removal rate of organic matter and there were.almost no difference between the two period.For the removal of ammonia nitrogen,operating long time,each process can have a more than 50% removal rate.Dosing reduction did not affect the effect of ammonia nitrogen removal.For the removal of nitrite nitrogen,Dosing reduction did not affect the effect of nitrite nitrogen removal.These processes can produce high quality water.When flux run at 30L/m2·h,membrane fouling can be effectively controlled,leading the growth of transmembrane pressure are slowly.Comparison of three short processes ultrafiltration technology,we found potassium permanganate had a significant effect on the removal of tryptophan and powdered activated carbon had a significant effect on the removal of fulvic acid.Finally,the paper analyzed the applicability of LJ water plant coagulation-ultrafiltration short process.The results show that the coagulation-ultrafiltration process was applicable to high turbidity water and could significantly resistance turbidity impact.It had a good removal rate of organic matter,ammonia nitrogen and nitrite,the removal rate were 37.2%,56.5% and 22.4% respectively.The effect of shielding microbes was significant and could greatly guarantee the biological safety of water.So,water quality indicators of waterworks could measure up the high quality of standards.The operation running in Low-flux and low-transmembrane pressure ways adopted by coagulation-ultrafiltration waterworks could have a good potential potential and flexibility,which could meet the actual demand for water supply.The physical cleaning "gas + water" could effectively remove the cake layer attaining to membrane surface,effectively improving the membrane flux and reduce the membrane pressure.Meanwhile,the chemical cleaning " Sodium hypochlorite and Citric acid " can effectively remove the deep membrane of pollution,greatly delayed the permanent membrane fouling.Physical cleaning and chemical cleaning is an important means to ensure the stable operation of ultrafiltration system.Physical cleaning could effectively delay membrane fouling and chemical cleaning could successfully control membrane fouling,leading the pollution rate of membrane system nearly remaining at zero.