Experimental Study Of The Oxidation Of Carbon Mud/high Density Precipitation /ultrafiltration Integrated Process

The composition of the surface water source is very complex,so water quality which be treated by Conventional drinking water treatment process can’t achieve new drinking water standards.Especially for the water from Yellow River reservoir which is polluted slightly,it is more difficult to deal with.High density sedimentation tank is a new type of sedimentation tank which includes coagulation and precipitation function.It is widely used to purify water with the characteristics of compact,high efficiency and flexibility.And it can exert a better effect when was used to dispose low turbidity water.However,due to the different water quality of the original water,the technology still has some problems to be solved.Aiming at low turbidity and micro polluted water for the Yellow River Reservoir,the subject puts forward an carbon mud/high density precipitation/ultrafiltration integrated process.This integrated process includes the carbon mud contact oxidation system and the ultrafiltration membrane system.The activated carbon was added to the high density sedimentation tank,and the activated culture pool was added to the carbonaceous sludge,so the carbon sludge contact oxidation system was formed.A pilot study on treating water of the Yellow River by immersion ultrafiltration membrane and coagulation sedimentation process.The test results show that the turbidity of the effluent is below 0.1NTU after treated by ultrafiltration membrane.However,the removal efficiency of organic matter by ultrafiltration membrane is very low,and the removal rate of UV₂₅₄54 and TOC is only 10.2%and 5.8%respectively.When adding PAFC 45 mg per litre of water(5mg/L with Al³⁺and Fe³⁺content),the removal rate of UV₂₅₄54 and TOC by coagulation sedimentation+ultrafiltration process is 16.2%and 11.3%,respectively.Therefore,coagulation sedimentation+ultrafiltration process has a bad treatment effect of UV₂₅₄54 and TOC to the water source which from Yellow River.Adding mud slag 120mg/L and powdered activated carbon 100mg/L in the carbonmudoxidation/highdensityprecipitation/ultrafiltrationcombined process.Then the system runs steadily by adjusting the dosage of PAFC.After 40 days of operation,the whole system has reached a stable state.And the removal rates of turbidity,UV₂₅₄,TOC,ammonia nitrogen and nitrite nitrogen for raw water were 50%,32%,26%,45%and 40%,respectively.The study of carbon sludge reflux contact oxidation system found that the biomass of carbon sludge was stable at 85×10⁷CFU/ml and the aerobic rate of per unit mass reached 0.45mgO₂/（min·g）.By scanning electron microscope,the species of microbes in the carbon sludge are mainly coccus and filamentous bacteria,so the sedimentation of the floc is better,the average particle size of the floc reaches 92.7μm.At this time,when the ratio of carbon to sludge reflux is 7%,the best condition of turbidity and organic matter removal is achieved.The removal efficiency of the organic matter with molecular weight of>1000 Daltons is better,the removal rate of THMFP is about 32.5%,and the dissolved microbial metabolites in the effluent from the carbon sludge contact oxidation system disappear completely.In the operation of combined process,if the carbon sludge contact oxidation system appears some problems,the mixture of carbon mud will be contained in the influent of ultrafiltration.It is found that the increase rate of the Trans-membrane pressure（TMP）of the ultrafiltration membrane is obviously accelerated when the concentration of the mixture of carbon and sludge in the influent of the ultrafiltration membrane reaches 20mg/L.When the concentration of carbon and sludge reaches40mg/L,the TMP is increased from 9.8Kpa to 50.1Kpa after only 8 days of operation,reaching the early warning value of the ultrafiltration membrane operation.Through the experiment,it is found that the membrane fouling can be effectively slowed down by the combined backwashing of gas and water and emptying of the membrane pool timely.