Study On A Novel Folded Plate Bioflim Reactor For Wastewater Treatment In Rural Areas

In recent years,although the level of material life of rural residents in China has been greatly improved,the construction of water supply and drainage facilities have been lagging behind,90% of rural wastewater discharged directly without treatment,which not only caused serious damage to the village environment,also cause great pollution to the water flowing through.Although researchers have been committed to the development of new wastewater treatment technology,but the problems of rural wastewater treatment are the difficulty of wastewater collection,equipment maintenance and operation cost.Our research group investigated 58 rural areas in Shanxi,Guangdong and Guizhou,and summed up the common demand of wastewater treatment of rural areas.According to our previous experience in the field of wastewater treatment equipment development,we treat the rural wastewater by folded plate biofilm reactor for the first time.This research studies the theoretical and application problems of this system for startup and operation.During the start-up stage,using ceramic plate of the rough surface and polymer fibers as carriers,more than 80% COD removal efficiencies as the success criteria of start-up,the biofilm thickness of polymer fiber wire reached 20 mm,which was 3 times of the ceramic tile board.In the later stage of the start-up phase,the biological membrane appeared two times obvious shedding in ceramic board,the removal efficiencies of COD and TN also had great fluctuation,but the biological membrane of polymer fibre always adhered firmly,the COD removal efficiencies was over 93%,and the total nitrogen removal efficiencies was over 60%,with polymer fibre as carrier has better performance and stability.The COD/TN is one of the most important parameter for biofilm degradation.With the gradual increase of COD/TN,the concentration of COD in effluent was stable within 100mg/L,the COD removal efficiencies reached more than 90%,the whole reaction system had a good performance for resistance to organic load impact.The NH₄⁺-N removal efficiencies decreased after a rapidlyincreased with the increase of COD/TN,at COD/TN was 14,NH₄⁺-N removal efficiencies reached a maximum value of 97.1%,and there was no obvious accumulation of nitrite and nitrate nitrogen?less than 3mg/L?.The whole reaction system reached a best performance for the simultaneous nitrification and denitrification.It must be pointed out that as the limitation of biofilm,TP removal effect was not obvious.In order to investigate the bacterial community shifts for different COD/TN,the high throughput sequencing analysis results showed that,at the Phylum level,the biofilm was mainly made up by Proteobacteria,Actinobacteria,Bacteroidetes,Firmicutes and Nitrospirarein,with the increase of influent COD/TN,Proteobacteria gradually increased?increased from 28% to 64%?,and Actinobacteria and Bacteroidetes decreased gradually.Measurement results of biomass showed that,the biomass decreased gradually with the increase of flow rate?reduced from 18.98 g VSS/g to 15.19 g VSS/g?,the measurement results of EPS also confirmed it,the contents of protein and polysaccharide were decreased with the increased flow rate.The monitoring data of DO showed,the drop rates of dissolved oxygen concentration gradually decreased.Considering the combined effects of scouring action for wastewater biofilm and dissolved oxygen efficiency to get a better processing efficiency and stable operation,the folded plate biofilm reactor flow should be set to 2 L/min.