Effects Of Filter Media On Treatment Of Carbon,Nitrogen And Phosphorus In Rural Domestic Sewage By Biofilter

The construction of"beautiful China"begins with the construction of"beautiful countryside".The random discharge of rural domestic sewage in China leads to serious ecological environmental problems,and it is urgent to effectively control it.Due to the constraints of economic and natural conditions,the vast rural areas of China should adopt low energy consumption,low cost and easy management of rural domestic sewage treatment technology.Therefore,this study took rural domestic sewage as the research object and designed a biological filter wastewater treatment process.Through screening,three kinds of fillers,ceramsite filler,elastic filler and polypropylene ball,were selected to investigate the effect of different fillers on the removal of pollutants during the film hanging period,the influence of pollution load,carbon-to-nitrogen ratio and temperature on the operation of different filler biofilters in the stable period,and the research on the characteristics of the biofilm of different filler biofilters under the optimal operating parameters.1.During the start-up and film-hanging stages,the amount of biofilm attached by different fillers was significantly different,the amount of biofilm attached to the surface of the ceramsite filler entered a stable period at about 28d,reaching 26.88mg/g,while the elastic filler and polypropylene balls were at 32d and 34d entered a stable period,which were 19.62mg/g and 16.78mg/g,respectively;the removal rate of COD and NH₄⁺-N of the ceramsite biological filter tended to be stable on the 28th day,shows that the ceramsite biofilter has successfully started to hang the membrane,which is 4d and 6d ahead of the elastic and polypropylene spheres,respectively.The start-up time of the ceramsite biofilter is the shortest,and the amount of biofilm attached to the surface is the highest.2.In stable operation stage,the pollutant treatment effect of biofilter is that the sewage treatment effect of ceramsite filler is better than that of elastic filler and polypropylene ball.The removal rate COD ceramsite filler can reach 96.3%,the effluent quality can reach the national sewage comprehensive discharge first class standard;the TP removal rate can reach 63.46%,the effluent quality is close to the national sewage comprehensive discharge second class standard;the NH₄⁺-N removal rate can reach 82.9%,the effluent quality can reach the national sewage comprehensive discharge second class standard;the TN removal rate can reach 67.6%,and the effluent quality can reach the national sewage comprehensive discharge first class standard.3.Pollution load,carbon-to-nitrogen ratio and temperature have different effects on the pollution treatment of different filler biological filters.The ceramsite filler has good carbon,nitrogen and phosphorus treatment effects under low,medium and high pollution load conditions,and the removal rate is higher at medium pollution load,and the removal rate of COD,TP,NH₄⁺-N and TN reaches 96.9%,64.2%,82.2%,and 68.9%;ceramsite fillers have good carbon,nitrogen,and phosphorus treatment effects under the three C/N conditions of 5:1,10:1,and 15:1,the removal rate is higher at 10:1,and the removal rates of COD,TP,NH₄⁺-N and TN are 95.6%,64.7%,81.3%and67.9%;the ceramsite filler is at 8°C,18°C and 28°C,under all temperature conditions,ceramsite filler have good carbon,nitrogen,and phosphorus treatment effects,the removal rate is higher at 28°C,the removal rates of COD,TP,NH₄⁺-N and TN are96.1%,63.9%,81.6%and 68.5%.4.The biofilm characteristics of different fillers are different.The biofilm amount（31.689mg/g）and dehydrogenase activity（44.589mg TF/g SS）of ceramsite filler are higher than those of elastic filler and polypropylene balls;fourier infrared spectroscopy（FTIR）shows that the hydroxyl（carbohydrate）and amino（protein）substances of ceramsite filler and the substance with protein group in amide I,II and III are higher than that of elastic filler and polypropylene ball,that is,the functional group and material composition of ceramsite filler are higher than that of elastic filler and polypropylene ball.5.There are significant differences in the biofilm EPS formed by different fillers.The biofilm EPS content shows that the T-EPS content of ceramsite filler（245.2mg/g VSS）,PN/PS value（2.76）and the proportion of TB-EPS in T-EPS（67.58%）are higher than those of elastic filler and polypropylene balls,that is,the ceramsite filler biofilm EPS secretion and structural stability are superior to elastic fillers and polypropylene balls,the ultraviolet spectrum and three-dimensional fluorescence spectrum show that the EPS of ceramsite filler biofilm,especially TB-EPS,contains tryptophan,tyrosine protein and humus substances more abundant than elastic filler and polypropylene ball.