Intensified Nitrogen Removal Of Kitchen Waste Fermentation Wastewater In An AOAA Process

Aiming at the problems of high-concentration ammonia nitrogen（HAN）,low carbon-to-nitrogen（C/N）ratio and insufficient carbon source for nitrogen removal in kitchen waste fermentation wastewater（KWFW）,the enhanced nitrogen removal technology in an Anoxic/Oxic/Anoxic/Anoxic（AOAA）system was developed.The AOA biofilm and activated sludge system with low C/N ratio and HAN wastewater based on partial nitrification and denitrification（PND）was developed,focusing on the degradation of pollutants in AOA system along the process.The microbial population and dominant functional bacteria of AOA system were analyzed by 16S r RNA high-throughput sequencing technology.On this basis,in order to further enhance the nitrogen removal efficiency,the first path was to add carbon source extracted from primary sludge into A₃-O₃ units.Therefore,the carbon source extraction technology for enhanced hydrolysis acidification of primary sludge based on iron and its compounds was systematically studied.Meanwhile,the AOAA-coagulation combined process treating KWFW based on extracted carbon source was investigated.The second path was to establish a bio-electrolysis coupling system in the A₂ unit of AOAA system to enrich autotrophic denitrifying bacteria.Attention was paid to the impact of current intensity on the nitrogen removal efficiency of system.Also,the nitrogen removal efficiency and microbial mechanism of bio-electrolysis coupling AOAA system treating KWFW was investigated.The main conclusions are as follows:After 27 days of operation,the AOA system based on PND was successfully developed.The removal rates of NH₄⁺-N,TN and COD in the biofilm system were83.45±0.82%,76.90±0.21%and 88.11±0.05%respectively,and the effluent concentration of NO₂^--N was 65.10 mg/L with nitrite accumulation rate of 98.42%.The removal efficiency of biofilm system was better than activated sludge system.Results showed that DO had a significant effect on the development of system,and the suitable DO for the biofilm system was 3.5±0.5 mg/L.The dominant denitrifying bacteria in the system were Chryseobacterium,Stenotrophomonas,Bacillus,Clostridium＿sensu＿stricto,Ottowia,Sphingobacterium,Gemmatimonas,Bradyrhizobium,Azospira and Rhodobacter.In the system,nitrogen removal was carried out synergistically by multi-paths such as partial heterotrophic nitrification-aerobic denitrification（HN-AD）,endogenous denitrification（ED）and heterotrophic denitrification（HD）.The effect of zero valent iron（ZVI）on sludge hydrolysis acidification was stronger than that of magnetite.Under the conditions of p H 9 and 55℃,the concentrations of SCOD and TVFAs in the control group were 8310±125 and 3819.09±84.51 mg/L respectively,the reduction of VSS was 27.91%,and the release of NH₄⁺-N and PO₄^3--P was 679.30±62.13 and 4.07±0.93 mg/L respectively.Compared with the control group,SCOD of magnetite group and ZVI group increased by 14.60%and 20.47%,TVFAs increased by 15.82%and 30.43%,VSS reduction increased by 5.66%and 36.30%,PO₄^3--P release decreased by 33.42%and 35.14%respectively with no significant decrease of NH₄⁺-N.The C/N ratio of additional carbon source from hydrolysis acidification had significant effect on nitrogen removal efficiency in A₃-O₃ process of AOAA system for KWFW.At C/N ratio of 3,the system had the highest nitrogen removal efficiency.The NO_x^--N removal rates of the biofilm and activated sludge system were 70.32%and 66.28%respectively,and TN removal rates were 78.81%and 76.12%respectively.The current intensity had a significant effect on the efficiency of bio-electrolysis coupling AOAA system treating HAN wastewater.Under the optimal current intensity of50m A,the nitrogen removal efficiency of biofilm electrolysis coupling system was better than that of activated sludge electrolysis coupling system,and the removal rates of NH₄⁺-N,TN and COD in biofilm system were 5.67%,6.07%and 0.22%higher respectively.The nitrogen removal efficiency of A₂ unit was significantly improved by bio-electrolysis coupling process,and the TN removal increased by 86.41%compared with that without electrolysis.The dominant denitrifying bacteria in the system were Chryseobacterium,Stenotrophomonas,Bacillus,Clostridium＿sensu＿stricto,Proteiniclasticum,Bradyrhizobium,Thermomonas,Ottowia,Gemmatimonas,Truepera,Brevundimonas and Rhodobacter.Results demonstrated that the nitrogen was removed by the synergism of partial HN-AD,ED,autotrophic denitrification and HD.At 30℃,the effluent NH₄⁺-N,TN,COD and BOD₅ of biofilm-electrolysis coupling AOAA-coagulation combined system for KWFW could satisfy the discharge standards specified in"Table 2"of"Pollution Control Standards for Domestic Waste Landfill Sites"（GB 16889-2008）.Among them,the average removal rates of NH₄⁺-N,TN and COD in AOAA system were 99.23%,98.34%and 93.0%respectively,and the average removal rates of COD in coagulation unit were 81.8%.The sharing rate of COD removal in AOAA system and coagulation unit were 94.2%and 5.8%,respectively.In this system,the dominant denitrifying bacteria were Chryseobacterium,Stenotrophomonas,Bacillus,Pseudomonas,Alcaligenes,Paracoccus,Proteoclasticum,Bradyrhizobium,Thermonas,Ottowia,Gemmatimonas,Truepera,Brevundimonas,Petrimonas,Luteimonas,Thiopseudomonas,Methylobacillus and Vitellibacter.The nitrogen removal of the system was carried out through the multi-path cooperation of partial HN-AD,ED,autotrophic denitrification and HD.