Study On The Enhanced Mechanism Of Reservoir Water Cross-flow Ultrafiltration For Biological Pretreatment

Due to the limited conditions of the northern water plant,the biological method has not been popularized and applied.The main reasons are low load,low temperature,and difficulty in starting.This experimental study takes into account that in the cross-flow filtration of the ultrafiltration membrane,the returned water contains microorganisms and organic matter that cannot pass through the ultrafiltration membrane.After returning to the biofilm pre-oxidation tank,the biological reaction tank is activated to solve the problem of low microbial load.Difficulties to deal with.The test raw water first enters the biological contact oxidation tank for full biodegradation,the effluent enters the ultrafiltration inlet bucket,the centrifugal pump presses the water into the cross-flow ultrafiltration membrane module for cross-flow filtration,and the cross-flow ultrafiltration water enters the water purification bucket for reverse flow.Flushing,the concentrated liquid of the cross-flow ultrafiltration membrane module and the backwashing waste liquid are returned to the biological contact oxidation tank for recycling treatment.This process is mainly aimed at the problem of poor removal of small molecular organics by traditional water purification processes.It increases biological contact oxidation for pretreatment,and uses microorganisms in biofilms to degrade small molecular organics in water;at the same time,cross-flow ultrafiltration membrane technology is adopted to ensure To improve the biological safety of the effluent of the biological contact oxidation tank,the cross-flow ultrafiltration concentrated water is returned to the biological oxidation tank without waste water discharge,and the microorganisms trapped by the ultrafiltration membrane are returned to the biological contact oxidation tank to ensure that there are sufficient microorganisms in the biological contact oxidation tank Degrade organic matter;at the same time,the cross-flow ultrafiltration membrane adopts aeration during filtration to form a gas-liquid two-phase flow,and the reflux water carries high dissolved oxygen back to the biological oxidation tank,providing an aerobic environment for microorganisms and effectively reducing energy consumption.Combining biological contact oxidation with cross-flow ultrafiltration treatment technology,optimizes the problems of low feed water treatment load of conventional biological oxidation method and low water output and high energy consumption of conventional dead-end ultrafiltration.At the same time,the treatment technology improves the solubility of small molecules.The removal effect of organic matter ensures the biological safety of the effluent,saves floor space,and reduces the energy consumption of water production.Increasing aeration during filtration to form a gas-liquid two-phase flow has an obvious strengthening effect on the cross-flow filtration process.When the aeration rate is 120 L/h,the hollow fiber membrane stable membrane flux is the largest.Compared with the single-phase flow cross-flow filtration when the aeration rate is 0 L/h,the stable membrane flux increases by 65%.However,when the aeration rate is greater than 120 L/h,if the aeration rate is further increased,the membrane flux not only does not increase,but decreases,which means that excessive aeration will cause the hollow fiber membrane cross-flow filtration system Negative impact,compared with the stable membrane flux when the aeration rate is 120 L/h,the aeration rate of 150 L/h and 180 L/h attenuates 5.88%and 11.76%,respectively.This shows that when the aeration rate exceeds 120 L/h,the stable membrane flux of the hollow fiber membrane module decreases with the increase of the aeration rate.The removal rate of cross-flow ultrafiltration for bacteria is 100%,and the reflux rate is basically stable at about 80%.This shows that the cross-flow filtration system has a very obvious effect on the retention of bacteria.After the biological contact oxidation,it can return most of the free bacteria and microorganisms in the water to the biological contact oxidation system.At the same time,it can return to the biological contact oxidation system.It can remove the shed and separated microorganisms on the biofilm caused by water conservancy impact and other factors to ensure the biological stability of the effluent.There are four different types of fillers:combined packing,soft fiber packing,elastic three-dimensional packing and fluidized bed packing.Under the same culture conditions,the final removal effect of the combined packing and soft fiber packing system on COD_Mnis not much different.For the final COD_MnThe removal effect is about 50%.The biofilm system cultivated by the combination of fillers and soft fiber fillers has a fast coating speed,and the removal effect of COD_Mnand ammonia nitrogen are better than the other two types of fillers.Better than the removal effect of elastic three-dimensional packing and fluidized bed packing.At the same time,it can also be observed that the combined filler and soft fiber filler system achieved stable removal of COD_Mnon the 10th and 14th days,respectively.The removal rate of COD_Mnby the biological contact oxidation combined cross-flow ultrafiltration system is 75%～80%,the concentration of COD_Mnin the effluent is below 1mg/L;the removal rate of ammonia nitrogen is about 96%,and the concentration of effluent ammonia nitrogen is below 0.5 mg/L;The turbidity removal rate is about 95%,and the effluent turbidity is below 0.1 NTU.In the removal process of COD_Mn,the removal rate of the biological contact oxidation part is 45%～50%,and the contribution is 60%;the removal rate of the cross-flow ultrafiltration system is 30%～35%,and the contribution is 40%.The biological contact oxidation combined cross-flow filtration pilot system still has a good removal effect when dealing with seasonal temperature changes.When the water temperature in winter is low（14°C）,the removal rate of ammonia nitrogen is guaranteed to be above 90%,and the removal rate of COD_Mnis also 68.1%,and the effluent quality still meets the"Standards for Drinking Water Quality"（GB5749-2006）.