| With the rapid development of China’s social economy,economic prosperity,and improved quality of life,it has also brought about severe water environmental pollution problems.Effective treatment and disposal of sewage is the core means to solve water environmental pollution problems.Long term practical experience has shown that the efficient removal of nutrients such as nitrogen and phosphorus from sewage is a bottleneck problem that restricts the upgrading and renovation of sewage plants.On the other hand,phosphorus is a non renewable natural resource.Efficient nitrogen and phosphorus removal while achieving effective recovery of phosphorus resources during sewage treatment is one of the hot topics in theoretical and technical research in the field of sewage treatment.Therefore,in view of the problems of high nitrogen and phosphorus wastewater,such as great harm and difficult treatment,this topic has constructed an integrated process of anaerobic Ceramic membrane bioreactor（AnCMBR）coupled with anaerobic fluidized bed reactor（AFB）,giving full play to the advantages of AnCMBR in high pollutant removal efficiency and good effluent quality,while combining with the crystallization of AFB carrier magnesium ammonium phosphate（MAP）to achieve nitrogen and phosphorus co recovery,and achieving effective control of AnCMBR membrane pollution by optimizing AFB carrier fluidization.The optimal carrier for the integrated reactor was selected in the study,and the effects of key factors such as carrier dosage,Mg/P,stirring speed,and reaction time on MAP crystallization phosphorus removal efficiency were systematically investigated.The integrated reactor was operated at the optimal level of each key factor,and the influence of hydraulic retention time during the operation stage of the AnCMBR-AFB integrated reactor on pollutant removal efficiency,nitrogen and phosphorus recovery characteristics,and membrane pollution control status was explored,The experimental results are expected to provide technical support for the promotion and application of the AnCMBR-AFB integrated process.The influence of key factors on MAP crystallization was systematically investigated.Screening out the key factors affecting MAP crystallization,including carrier dosage,reaction time,stirring speed,and Mg/P;A four factor and four level orthogonal experiment was constructed with the phosphorus removal rate as the response value,and the results of the orthogonal experiment were analyzed using SPSS software.The results showed that the significance of the four factors on phosphorus removal rate was as follows:reaction time>Mg/P>carrier dosage>stirring speed;The optimal crystallization condition is:the carrier dosage is 5 g,the reaction time is 90 minutes,the stirring speed is 125 r/min,and the Mg/P is1.4.SEM EDS and XRD microscopic characterization indicate that MAP crystals can be generated on the surface of the activated carbon carrier.The AnCMBR-AFB integrated reactor was validated and optimized through flow field simulation;The flat Ceramic membrane in the reactor has good water treatment characteristics.Under the pressure of 30 KPa,its clean water flux can reach 464.83L/（m2·h）.The AnCMBR-AFB integrated reactor treats simulated septic tank wastewater,and the critical flux of the flat Ceramic membrane is 31.46 L/（m2·h）.The AnCMBR-AFB integrated reactor was successfully started after about 20 days,with a COD removal rate of 80%,UV254stable at around 0.06 cm-1,effluent chromaticity reduced to 0.01 A,and an average turbidity value of 0.522 NTU;The TMP of the flat Ceramic membrane in the start-up stage is divided into three stages:1-5 d large pollutants are adsorbed on the membrane surface and fine particles are accumulated in the membrane pores;6-11 d pollution particles are enriched on the membrane surface,forming a loose mud cake layer;12-16 d mud cake layer starts to compact,forming a dense gel layer;During the start-up stage,the nitrogen and phosphorus concentration in the effluent of the reactor is relatively stable,with an average nitrogen recovery rate of 23.03%and an average phosphorus recovery rate of42.09%.There is a significant difference in the impact of HRT on the removal efficiency of various pollutants in the AnCMBR-AFB integrated reactor.The HRT is shortened from 18hours to 14 hours,and the COD removal rate gradually decreases from 84%to 75%.Indicators such as UV254,chromaticity,and turbidity remain stable;HRT has a significant impact on the membrane fouling cycle.As HRT shortens,the membrane fouling cycle also shortens,and TMP cannot recover to the level of the new membrane after backwashing;The microbial metabolites in the sludge mixture and membrane surface cake layer are mainly SMP and EPS,and the protein content is higher than that of polysaccharides.The micro characterization of contact angle,SEM-EDS,and infrared spectroscopy showed that the new film had good hydrophilicity;Amides,saturated hydrocarbons,and other substances are the main organic compounds that cause membrane fouling,and inorganic metal ions also have a significant impact on membrane fouling;Physical cleaning can only remove some pollutants from the membrane surface and pores,and cannot completely restore the membrane flux;The impact of HRT on nitrogen and phosphorus recovery is relatively small,with an average recovery rate of 43.34%for phosphorus and 23.20%for nitrogen;Microscopic characterization shows that the surface of the carrier in the reactor is covered with a smooth biofilm,while MAP crystallization is generated. |
