Study On The Efficiency And Mechanism Of Bio-Cage-Coupled Plant Purification Tank For Rural Sewage Treatment

With the continuous improvement of the level of urbanization in my country,although the urban domestic sewage has been effectively treated.However,about 36%of my country’s population still lives in rural areas,and the rural domestic sewage treatment technology is relatively backward.The rural domestic sewage problem has become an important environmental problem in my country.The biological tumbler is a small integrated biofilm treatment equipment,which has the advantages of strong decontamination ability and load impact resistance,rich microbial community,low treatment cost and sludge yield.The plant purification tank has the advantages of constructed wetlands and occupies a small area.It can realize the economic benefits of pollutant removal in water and sewage treatment by cultivating aquatic crops.In this study,a rural domestic sewage treatment process with biological cages coupled with plant purification tanks was constructed,and the effect of the process in the treatment of rural domestic sewage was studied.Technical Support.The main contents and conclusions of this study are as follows:（1）Taking the simulated rural domestic sewage as the research object,research on start-up mode and parameter optimization of the bio-rotating cage reactor was carried out.The biofilm activity and pollutant removal effect during the start-up process of the biological tumbler reactor were studied under the rotating speeds of 4r/min,6r/min and 8r/min respectively.The results show that,compared with the startup modes of 6r/min and 8r/min,the biofilm obtained by the bio-rotating cage reactor under the startup mode of 4r/min is thicker,the interior is more compact,the bacteria on the surface of the biofilm are more abundant,and the pollutants are removed.The best effect;the biofilm thickness is 2.5～3.0mm,the SOUR is 0.2156 mg_˙O₂/g_˙MLVSS_˙min,and the removal rates of COD,NH₄⁺-N,TN,PO₄^3--P are 91.39%,99.99%,75.30%,respectively,68.48%.Therefore,the reactor started at4 r/min was determined as the main reactor for the follow-up research,and the optimization of parameters such as rotational speed,influent COD concentration,influent C/N,and HRT was carried out.The results showed that when the rotation speed was 6r/min,the COD concentration of the influent water was not less than 300mg/L,the C/N of the influent water was not less than 6:1,and the HRT was 24h,the biological cage had the best removal effect of pollutants.The polysaccharide protein was measured on the biofilms of the inoculated sludge,the start-up completion stage and the parameter optimization stage respectively;the results showed that the biofilms in the parameter optimization stage had high polysaccharide and protein content,indicating that the biofilms after parameter optimization were optimized.The performance is better;Fourier transform infrared spectroscopy shows that the peak intensity of polysaccharides in biofilm EPS at 3200～3500cm^-1is significantly enhanced.（2）The nitrogen and phosphorus purification ability was screened for 5 aquatic plants including onion,cabbage,cress,tomato and water spinach,and cress was selected as the follow-up experimental plant comprehensively.Under the conditions of hydroponics,soil culture,filler culture,soil:filler=1:4,soil:filler=1:1,soil:filler=4:1,the research on the removal effect of pollutants in the plant purification tank was carried out.The results showed that the order of strength of TN removal is soil:filler=4:1>soil:filler=1:1>soil:filler=1:4>soil culture>filler culture>hydroponic culture,for PO₄^3--P The order of removal strength is soil:filler=4:1>soil:filler=1:1>soil culture>soil:filler=1:4>filler culture>hydroponics;considering the effect of nitrogen and phosphorus removal,soil:Filler=4:1 is the optimal soil cultivation method.The research on the removal of N and P in the purification tank was carried out under the condition of soil:filler=4:1.The results showed that the removal contribution rate of N in the plant purification tank was other（56.13%）>plant absorption（21.23%）>soil accumulation（5.04%）>zeolite adsorption（4.94%）,and the contribution rate to P removal was soil accumulation（40.26%）>plant absorption（23.64%）>zeolite adsorption（21.15%）>others（3.62%）.（3）Under the optimal operating conditions,the pollutant removal performance and operation stability of the biological turret coupled with the plant purification tank in the treatment of rural domestic sewage were studied.The results show that when the influent COD,NH₄⁺-N,TN,and TP concentrations are 80～165mg/L,20～60mg/L,23～60mg/L,and2～2.5mg/L,respectively,the combined process has a good effect on COD,NH₄⁺-N,TN and TP gradually increased,and the final removal rates were 75%,99%,42%,and 74%,respectively.The effluent concentration met Chongqing’s"Water Pollution Discharge Standard for Centralized Rural Domestic Sewage Treatment Facilities"（DB 50/848-2021）Level 1 standard.The results of scanning electron microscopy showed that the filamentous bacteria encapsulated the bacteria together,the biofilm was denser and formed into clusters.,the biofilm can still maintain good activity.（4）Sequencing and analysis of the microbial community structure was carried out on the sludge samples and biofilm samples of the biological cage under stable operating conditions at different stages,and the root samples in the plant purification tank,to explore the changes of the microbial community under different operating stages,and to analyze the microbial community at different classification levels.At the taxonomic level,the microbial community structure characteristics were analyzed.The results showed that in the stage of parameter optimization and the stage of treating actual rural domestic sewage,the biological classification of biological cages was dominated by Proteobacteria at the phylum level,and there were great differences at the genus level at each stage.After the actual rural domestic sewage treatment,the dominant Thiothrix genera in the biofilm decreased to 5.66%,but other genera were less affected by the actual wastewater.The main dominant bacterial genera were Nitrospira,norank＿f＿＿JG30-KF-CM45,Thiothrix,Phreatobacter,Solimonadaceae,with a richness of more than 30%;Proteobacteria dominated at the phylum level in the simulated wastewater stage and the actual wastewater stage in the plant purification tank,and there were great differences in each stage at the genus level.The root microorganisms at the genus level are mainly Rhodocyclaceae and Comamonadaceae.After treating the actual wastewater,Rhodocyclaceae,Methyloversatilis,and unclassified＿k＿＿norank＿d＿＿Bacteria at the genus level increase to a certain extent,and the abundances are 20.81%,2.73%,and 1.96%,respectively.In addition,new dominant genera were discovered,such as Roseiflexaceae,Rhizobiaceae,Desulfovibrionaceae,Pleomorphomonadaceae.