Study Of An Advanced Dynamic Membrane In Separation Process Of Sewage Treatment

In this study an innovative dynamic membrane bioreactor?DMBR?was implemented from a stainless-steel mesh filter,which was used as a support material,and activated sludge used as an adsorption and filtration interface.The new DMBR is dedicated to solving the key problems such as unstable sedimentation effect of sedimentation tank,excessive TP of effluent,large area,high power consumption and long time consumption.Firstly,a stainless steel membrane filtration device was designed and fabricated.The phosphorus-containing simulated wastewater?TP 2mg/L?was subjected to a chemical coagulation precipitation and coagulation filtration comparison experiment.The results showed that the filtration effect of stainless steel membrane with a pore size of 25?m was better than that of precipitation separation after adding coagulant and polymer organic flocculant to the wastewater.The removal rate of TP was 91%.The discharged wastewater of TP was stable below 0.2mg/L,and was even better.TP can also meet the transformation standard after adding coagulant and calcium carbonate to the wastewater.Compared with the ordinary chemical coagulation precipitation method,the coagulation filtration method shortened the separation time and the area of the precipitation while ensuring the water quality effect.Secondly,the stainless steel membrane filtration device was submerged in the reaction tank of the sequential batch activated sludge process?SBR?to construct a new type of dynamic membrane bioreactor?DMBR?.The pollutant indicators total phosphorus?TP?,chemical oxygen demand?COD?and ammonia nitrogen?NH₄⁺-N?were compared through dynamic membrane filtration and sedimentation in the treatment of domestic sewage.Samples of continuous water inflow,precipitation effluent,and new DMBR effluent were significantly,but the removal of COD and TP was significantly improved.COD reached92.2%and TP reached 91.5%.The index of sewage treatment is better than that of activated sludge precipitation.Thirdly,the key technical issues such as the running stability and membrane fouling of dynamic membranes in SBR tanks were investigated.The sludge concentration of the new DMBR can be more than doubled than that of the activated sludge method,reaching more than 6000mg/L.The increase of biomass greatly promoted the degradation rate of pollutants in wastewater.The sludge concentration?MLSS?,sludge index?SVI?,sludge biological phase observation and Fourier infrared spectroscopy?FTIR?analysis showed that the new DMBR exhibited good adsorption and biodegradability when the activated sludge concentration was about 6000mg/L.It helped to increase biomass and sludge particle agglomeration,and further matched the pore size of stainless steel mesh.It improved dynamic retention effect and operating stability,and also shortened sludge aeration time.Meantime,the relationship between the Zeta potential,sludge particle size and extracellular polymer?EPS?at different points in a cycle had been analyzed.It showed that the new DMBR process exhibited excellent filtration performance.The more EPS in the sludge and lower the Zeta potential contributed to the formation of larger particle flocs.The volume density of the sludge particles with a pore size of less than 25?m stainless steel mesh was only 5.32%.EPS can indirectly avoid the generation of membrane fouling and realize the solid-liquid rapid separation of pollutants.At last,it is obtained that the new DMBR was operated under high flux conditions through the analysis of the liquid flux,gas permeability and pollutant discharge flux of the stainless steel mesh filter.The activated sludge and its aeration were provided to the dynamic membrane material and the automatic regeneration cycle process.The sludge adhered to the membrane surface was back to the sewage by the force of the fluid generated by the aeration,which effectively avoiding the generation of membrane pollution.Therefore,the new SBR-DMF process has achieved the replacement of the secondary sedimentation tank in theoretical practice,and solved the key problems of TP,large area,high power consumption,and long time consumption.This technology has important reference value and broad application prospects in the process of sewage treatment.