Study On The Capacity Of Secondary Treatment Of Intercepted Sewage In Urban Sewage Plant In Rainy Season

Rainwater in rainy season intercepted by available intercepting combined sewage plant is only in the primary treatment,carrying a large number of organics,nitrogen and phosphorus into the receiving water,which poses a serious threat to the water environment with insufficient environmental capacity.To upgrade the secondary treatment of intercepted rainwater has become the key to water environment protection.In this paper,the upgraded secondary treatment of intercepted rainwater in the intercepting combined sewage plant is taken as the research object.By adjusting the operation condition of biological unit in an non-engineering measure,the capacity of the secondary biological treatment unit to absorb intercepted rainwater is enhanced,and the pollution control of intercepted rainwater is realized.This paper focuses on the influence of sludge concentration and addition of filler on the capacity of upgraded secondary treatment-SBR/A~2O to absorb intercepted rainwater so as to determine key parameter to enhance the capacity of systems absorbing rainwater under designed working conditions.Based on this,it explores the influence of sludge concentration and addition of filler on the capacity of upgraded secondary treatment-SBR/A~2O to absorb intercepted rainwater under the alternate operation mode of dry season and rainy season and the microbial community structure and dominant functional bacteria in SBR system both in dry season and rainy season by using 16SrRNA Amplicon-a high-throughput sequencing technology.The main conclusions are as follows:By increasing the sludge concentration and adding filler the efficiency and the capacity of SBR treatment system absorbing rainwater are significantly improved.In rainy season,when the C/N of sewage is 7.5,5.22 and 3.76,the sludge concentration increases from 4g/L to 6g/L and 8g/L,the net reduction of COD、TN in the reactor increaseing increasing.In order to reach a class A standard of GB18918-2002 urban sewage treatment,when the sludge concentration is 4g/L and 6g/L,for the C/N of sewage in rainy season being 5.22,the reactor can absorb 1.5 times the amount of water in dry season;when the sludge concentration is 8g/L,it can absorb twice the amount of water in dry season;for the C/N of sewage in rainy season being 3.76,when the sludge concentration is 8g/L,it can absorb once the amount of water in dry season.When add filler,the net reduction of TN and COD in SBR treatment system with filler increases,higher than that in conventional SBR system.With the goal that the effluent meets a class A standard of GB18918-2002 urban sewage treatment,when the C/N of sewage in rainy season are 7.5 and 5.22,SBR reactor with filler can absorb twice the amount of the water in dry season;for C/N of sewage in rainy season being 3.76,it can absorb 1.5times the amount of the water in dry season and twice the amount of the water in dry season based on a class B standard.There is no significant difference in the phylum level of microbial community in SBR System with or without addition of fillers in dry season and rainy season,but there was significant difference in the genus level of functional bacteria.The relative abundance of AOB and NOB bacteria in SBR System in rainy season is higher than that in dry season while the relative abundance of denitrifying functional bacteria in dry season is higher than that in rainy season.There are more species of denitrifying functional bacteria in rainy season than in dry season.The similarity of microbial community in SBR system is higher in dry season and rainy season while the similarity of microbial community is lower in SBR system with filler in dry season and rainy season.The dominant denitrifying functional bacteria in SBR System in dry season are Nitrospira,Other-f-Gemmataceae,Other-f-Nitrosomonadaceae,Other-f-Pirellulaceae,Gemmata and Nitrosomonas;there is another Rhodocyclus in rainy season than in dry season.The abundance of AOB bacteria in SBR System in dry season and rainy season is 5.10%and 7.47%,and the relative abundance of NOB bacteria is 2.51%and 3.41%respectively.There are mainly noclassified-f-Comamonadaceae,Other-f-Chitinophagaceae,Comamonas,lanctomyces,Paracoccus in the denitrification functional bacteria in SBR System in dry season,and there is another rubrevivax in rainy season than in dry season.The relative abundance of dominant denitrification functional bacteria in the SBR System in dry season and rainy season is 26.33%and 16.97%.The dominant AOB functional bacteria in the SBR system with filler in dry season are Other-f-Nitrosomonadaceae;the NOB functional bacteria are rhodocyclus and Nitrospira,and the denitrifying functional bacteria are dechloromonas,Flavobacterium,zooglobe,cytohagaceae,pseudoxandromias and comanamonas.In the SBR System with filler in rainy season,AOB functional bacteria mainly includes other-f-nitrosomonadaceae,other-f-gemmataceae,other-f-pirellulaceae;NOB functional bacteria mainly includes Nitrospira and rhodocylus;denitrifying functional bacteria mainly includes nonclassified-f-comaonadaceae,other-f-chitinophagaceae,zooglobe,dehloromonas and brachymona.The abundance of AOB bacteria is 1.43%and 3.34%;the abundance of NOB bacteria is 17.89%and 2.08%;the total relative abundance of denitrifying bacteria is 39.40%and 17.10%respectively.By increasing the sludge concentration and adding filler the efficiency and the capacity of A/A/O treatment system absorbing sewage in rainy season are significantly improved.In rainy season,when the C/N of sewage is 3.76 and the water inflow equals to that in dry season,the sludge concentration increases from 4g/L to 6g/L and 8g/L,the net reduction of TN,COD and TP increasing.In order to reach a class A standard of GB18918-2002 urban sewage treatment,when the sludge concentration is 8g/L,it can absorb once the amount of water in dry season.When the effluent reaches a class B standard,the sludge concentration being 4g/L,6g/L and 8g/L,with increasing efficiency the reactor can absorb 1.5 times the amount of dry season water.By adding filler,when the C/N of sewage in rainy season is 3.76,the net reduction of TN,TP and COD in the A/A/O treatment system with filler increases by 168mg,6.9mg and 278.1mg respectively,higher than that in the conventional A/A/O system.With the goal that the effluent reaches a class A standard of GB18918-2002 urban sewage treatment,it can absorb once the amount of the water in dry season,and twice the amount of the water in dry season based on a class B standard.