Practice Of MBR+RO Treatment Process In Municipal Wastewater Treatment Plant

Urban sewage treatment plant is the main means of effective control of urban sewage,at present,the standard of sewage treatment plant must be improved because of the water pollution is becoming more and more serious.Therefore,the country has invested a large amount of capital and manpower for the construction of water treatment infrastructure.In the transformation of sewage treatment plant,membrane technology has been widely concerned by the society because of its strong capacity to deal with sewage and the stability of water effluent.But membrane technology is not mature enough,and it has not been widely used in China.It is necessary to strengthen the related research of membrane technology and improve the efficiency of sewage treatment.Based on the latest research results of internal and external membrane technology,this paper uses the combined process of MBR+RO to treat sewage.The purpose of this study is to investigate the economy and feasibility of the experiment,the effects of MBR film on the removal of COD,NH₃-N,TN,TP and turbidity in sewage have been analyzed.In addition,the membrane fouling is common during the use of MBR film.The cleaning methods of membrane fouling were investigated and the suitable membrane cleaning method was explored.In order to further improve the water quality of sewage treatment,the RO membrane was used for deep treatment of sewage after the effluent of MBR membrane.The results showed that the RO film has good treatment effect on the conductivity,COD and other indexes of sewage,so it is feasible to use RO film for deep treatment of sewage after the MBR film,the main research results are as follows:1.Only using MBR membrane reactor,with the influent factors,such as pH 7-8,COD 100-400 mg/l,TN 10-50 mg/l,NH₃-N 5-20mg/l,MBR membrane pool MLSS8000-13000 mg/l,reflux ratio 300%.The average value of the effluent COD is 20.8mg/l,the removal rate is 85%,the average value of the effluent TN is 11.44 mg/l,the removal rate is 51.8%,the mean value of NH₃-N is 0.27 mg/l,and the removal rate is98%.After adding carbon source,the removal rate of COD and TN increased to 92%and 75%respectively,and the removal efficiency was greatly improved.Then,the anaerobic tank is opened,the removal efficiency of TP reached 40.6%,the average value of 1.63 mg/l of effluent TP,for further removal of TP,PAC and phosphorus removal test,from the economic and considering the removal effect,when the dosage of PAC is 30mg/l,the removal rate of TP reached 82%.2.During the test,the MBR film maintained a 20 days operation under the condition of the cross membrane pressure difference of<0.05MPa.When running to39d,the transmembrane pressure increases rapidly,the membrane flux decreases,and the water output of the MBR film decreases,and the membrane should been cleaned.The cleaning results showed that the best effect was achieved by1%sodium chlorate combined with2%oxalate,the membrane flux recovered to more than 80%of the initial membrane flux,and the recovery of membrane flux by other cleaning methods was less than 70%.3.After the sewage is treated with the MBR membrane,some of the pollutants are removed.The effluent from the MBR membrane is connected to the RO membrane for the depth treatment of the sewage.The electrical conductivity of RO is 0.01-0.06 ms/cm,COD<30 mg/l,and the turbidity is basically 0.Because the water quality of the MBR film is good,the pollution to the RO film is very small.It is only necessary to add the scale inhibitor to the RO membrane to prevent the fouling of the film.During the test,the RO film was not polluted,so the membrane has not been cleaned.By adding the technology of MBR+RO to the technology of the original wastewater treatment plant,the wastewater treatment effect can be effectively enhanced.The research results can provide reference for the upgrading and optimization of urban sewage treatment plants.