Pilot Study On Backpulsing Based Highly Adaptive Emergency Water Purification Device

China is a country with frequent natural disasters.The emergent water supply after disasters has always been a hot spot in the field of drinking water safety.In recent years,with the development of materials technology,various emergency water supply technologies and emergency water purification equipment have been developed at domestic and foreign.However,the existing emergency water purification device has poor water quality adaptability and mobility,and may run instability under extreme water quality conditions.To solve these problems,this project has completed the preliminary design of a highly adaptive ultrafiltration based emergency water purification device.In order to further improve the mobility and adaptability of extreme water quality,backpulsing was proposed to clean the ultrafiltration membrane.The control of the ultrafiltration membrane fouling by backpulsing and the optimization of the backpulsing was studied.An optimized pilot study based on backpulsing was carried out for four typical post-disaster water quality to improve the adaptability of multiple water quality.Backpulsing could effectively control membrane fouling.Compared with the traditional backwashing,under the initial flux of 80LHM,the backpulsing reduced the flux attenuation of the ultrafiltration membrane by 82.99%,increased the water yield by74.34%,decreased the irreversible pollution by 69.58%,and increased the particulate pollutant transmission by 37.04%.So the backpulsing has impoved the adaptability of emergency water purification device under extreme water quality of 200NTU of turbidity.The advantage of backpulsing on membrane fouling control decreased as the membrane flux increased.Compared with the traditional backwash,the decay rates of flux at 80,100and 150 LHM are reduced by 82.99%,61.63%and 52.56%,respectively.Based on the membrane cake formation model,the relationship between specific flux and filtration time was established.The effects of flux,backwashing pressure and backwashing time on specific flux and optimal filtration time were studied.The results showed that under the initial flux of 80LHM,backwashing pressure of 450KPa,and backwashing time of 2s,the maximum flux ratio of the experiment and theory was 0.681and 0.706,and the optimal filtration time was 25s and 60.6s respectively.An optimized pilot study of membrane materials and fluxes was carried out for micro-polluted raw water.The results showed that the membrane material and flux had little effect on the removal efficiency?p>0.05?.However,the membrane material and flux had great influence on the operation stability.Under the 40LHM flux,the PVDF ultrafiltration membrane run most stable during the pilot test and the transmembrane pressure only increased by 35KPa.The indicators such as turbidity,NH₄⁺-N and COD_Mnn treated by hydrocyclone/ultrafiltration/nanofiltration process met the“Chinese Sanitary Standards for Drinking Water”An optimized pilot test of dosage of the agent and pretreatment was carried out for high algae water.The results showed that the optimal dosage of the agent was PAM 0.5mg/L and PAC 9 mg/L?calculated as Al₂O₃?.The removal efficiency of pollutants by coagulation sedimentation was higher than that of medium filtration.Removal of the turbidity,chlorophyll a,COD_Mn and UV₂₅₄ were increased by 30.59%,46.09%,45.34%and 39.6%,respectively.The pre-chlorination did not improve the removal rate obviously?p>0.05?.The transmembrane pressure of ultrafiltration with and without pre-chlorination reached 110KPa or more with medium filtration as pretreatment.The transmembrane pressure of ultrafiltration with and without pre-chlorination reached 24.5KPa and 6.5KPa with coagulation sedimentation as pretreatment,respectively.Considering that residual chlorine will attenuate the nanofiltration membrane flux,ClO₂ was not added during coagulation sedimentation.The optimization experiment of the dosage of the agent was carried out for the highly turbid water.The results showed that the PAM 1 mg/L and PAC 20 mg/L?calculated as Al₂O₃?had the best effect on settling ability of flocs and turbidity removal.During the pilot test,COD_Mn and turbidity of coagulation sedimentation/ultrafiltration producing water can meet“Chinese Sanitary Standard for Drinking Water”.The COD_Mn,turbidity,TDS,hardness,Na⁺,Cl^-,SO₄^2-and F^-of hydrocyclone/ultrafiltration/reverse osmosis process producing water all meet“Chinese Sanitary Standard for Drinking Water”.Through the optimized pilot test under various water quality,the optimization of emergency water purification device was obtained,and adaptability of the device under multiple water quality was improved.