Study Of Ceramic Membrane-Nanofiltration Membrane Coupling Treatment Of Biogas Slurry

This paper addresses the problems of poor pretreatment effect,low efficiency and mismatch between membrane concentration process and raw material concentration,serious membrane contamination and high operation cost of membrane concentration treatment,focusing on the effects of different pore size ceramic membranes and process parameters on pretreatment effect of biogas and filter aid on pretreatment effect,co mparing and analyzing the effects of different operating pressures and concentration multipliers on nanofiltration membrane treatment of biogas slurry,and analyzing the effect of using The effects of different operating pressures and concentration multipl iers on nanofiltration membrane treatment were compared and analyzed.The main research results are shown as follows.（1）In this study,the pretreatment process of biogas slurry using ceramic membrane filtration device with two pore size ceramic membranes was studied to investigate the variation of membrane flux and pretreatment effect and the effect of adding filter aid.The results showed that ceramic membrane filtration was more effective as pretreatment of biogas slurry before membrane,and when the optimum membrane pore size was 0.05μm,the operating pressure was0.24 MPa and the concentration multiplier was 3.5 times,the The membrane flux of ceramic membrane can reach 296 L/（h·m²）,and the removal rates of SS and COD can reach 97.5%±0.2%and 52.9%±2.6%respectively when the concentrations of suspended solids（SS）and chemical oxygen demand（COD）of ceramic membrane influent are 308±33.5 mg/L and 3228±121.3 mg/L respectively;the removal rates of ammonia nitrogen（NH ₄⁺-N）and total nitrogen（TN）of ceramic membrane influent can reach 97.5%±0.2%and 52.9%±2.6%respectively.total nitrogen（TN）,total phosphorus（TP）and total potassium（TK）at concentrations of 511±25.6 mg/L,723±29.5 mg/L,31.6±2.4 mg/L and 445±24.1 mg/L,respectively,the remo val rates could reach5.3%±0.2%,8.5%±0.2%,48.4%±0.3%and 14.3%±0.3%,respectively.With the cleaning method of 1%nitric acid（HNO₃）solution-1%sodium hydroxide（Na OH）solution+0.05%sodium hypochlorite（Na Cl O）solution-water,the membrane flux recovery of the ceramic membrane could reach 99%±0.5%;when 2%activated carbon filter aid was added,the membrane flux of 0.05μm pore size ceramic membrane could reach 468 L/（h·m²）,and SS,COD,NH₄⁺-N,TN,TP and TK removal rates were increased by 1.3%,9.6%,2.2%,2.4%,15.9%and0.2%,respectively.（2）Through the comparative analysis of the nanofiltration membrane concentration process parameters,when the optimum operating pressure was 0.6 MPa and the concentration multiplier was 4 times,the membrane flux of the nanofiltration membrane in the device could reach 26±2.6 L/（h-m2）when the influent SS,COD and NH₄⁺-N concentrations were 3.6±0.5mg/L,1210.6±45.6 mg/L and 47.6 mg/L,respectively.45.6 mg/L and 472.6±8.3 mg/L,the removal rates after nanofiltration treatment could reach 100%,73%±0.2%and 25.4%±0.1%,respectively;when the influent TN,TP and TK concentrations were 644.2±12.6 mg/L,11.3±1.6mg/L and 380.5±14.5 mg/L,respectively,the concentrations of TN,TP and TK concentrations were 1.5 times,2.3 times and 1.7 times of the influent water,respectively.（3）The study of concentrated treatment of biogas using ceramic membrane-nanofiltration membrane coupling process,when the total nutrient（TN+TP+TK）of the influent biogas of the device was 1200±56.7 mg/L,the total nutrient（TN+TP+TK）in the mixed concentrated solution was 1496.3±21.3 mg/L,and the nutrient concentration was less enhanced.The SS and TP contents in the permeate were less than 1 mg/L,and the COD concentration was 327±19.6 mg/L,both of which were lower than the emission concentration in the Emission Standards for Pollutants from Livestock and Poultry Farms（GB18596-2001）,and the NH₄⁺-N concentration in the permeate of the nanofiltration membrane was still as high as 353.3±5.2 mg/L.The ceramic-nanofiltration membrane concentration process had a better retention e ffect on SS,COD and TP.The ceramic-nanofiltration membrane concentration process has good retention effect for SS,COD and TP,but poor retention effect for NH ₄⁺-N.Based on the energy consumption and membrane depreciation of the ceramic-nanofiltration membrane concentration process,the operating cost of biogas concentration treatment was calculated to be about 29.23RMB per ton of biogas slurry.