Study On Removal Mechanism And Influencing Factors Of Ammonia Nitrogen And Organic Nitrogen In Subsurface Infiltration Water System

The pilot subsurface infiltration wastewater system（SWIS）was used to study the removal mechanism and influencing factors of ammonia nitrogen（NH₄⁺-N）and organic nitrogen in this paper.This study will provide theoretical foundation for the research on intensified nitrogen removal and regulation of operational parameters,promote the use of SWIS in decentralized domestic wastewater treatment.The main conclusions are shown as follow:The study of the restart-up period of the SWIS showed that: the restart-up period for COD,NH₄⁺-N and TP were 15 d,17 d and 16 d,respectively.As a whole treatment system,its restart-up period would be the longest one.So its restart-up period was 17 d.After its restart-up period completed,the removal rates of NH₄⁺-N,COD and TP were more than 83%,80% and 90%,respectively.The removal mechanism and influencing factors of NH₄⁺-N in the SWIS showed that: the optimal operational conditions of NH₄⁺-N removal were 0.10 m3/（m2·d）for hydraulic loading rate,250-260 mg/L for optimal influent organic concentration,3:1 for C/N ratio and 2:1 for wet and dry ratio.Under such conditions,the removal rates of COD,NH₄⁺-N and TP were more than 90.8%,88.1% and 87.7%.When the hydraulic loading rate was 0.10 m3/（m2·d）,the proportion of ammonia volatilization for nitrogen removal was 3.5%,the nitrification and denitrification for nitrogen removal was 70.8% and soil adsorption for nitrogen removal was 16.5%.When the influent organic concentration was 250-260 mg/L,the proportion of ammonia volatilization for nitrogen removal was 3.6%,the nitrification and denitrification for nitrogen removal was 74.3% and soil adsorption removes nitrogen was 15.9%.When the C/N ratio was 3:1,the proportion of ammonia volatilization for nitrogen removal was 5.7%,the nitrification and denitrification for nitrogen removal was 71.6% and soil adsorption removes nitrogen was 12.6%.When the wet and dry ratio was 3:1,the proportion of ammonia volatilization for nitrogen removal was 4.3%,the nitrification and denitrification for nitrogen removal was 69.4% and soil adsorption for nitrogen removal was 17.6%.The removal mechanism and influencing factors of organic nitrogen in the SWIS showed that: the optimal operational conditions of organic nitrogen removal were 0.10 m3/（m2·d）for hydraulic loading rate,250-260 mg/L for influent organic concentration,3:1 for C/N ratio and 1:2 for wet and dry ratio.Under such conditions,the removal rates of COD,organic nitrogen and TP were more than 87.9%,66.3% and 89.1%.When the hydraulic loading rate was 0.10 m3/（m2·d）,the proportion of ammonia volatilization for nitrogen removal was 4.2%,the nitrification and denitrification for nitrogen removal was 55.2% and soil adsorption for nitrogen removal was 6.9%.When the influent organic concentration was 250-260 mg/L,the proportion of ammonia volatilization for nitrogen removal was 4.2%,the nitrification and denitrification for nitrogen removal was 57.8% and soil adsorption removes nitrogen was 26.6%.When the C/N ratio was 3:1,the proportion of ammonia volatilization for nitrogen removal was 4.9%,the nitrification and denitrification for nitrogen removal was 50.8% and soil adsorption for nitrogen removal was 11.0%.When the wet and dry ratio was 1:2,the proportion of ammonia volatilization for nitrogen removal was 3.1%,the nitrification and denitrification for nitrogen removal was 57.2% and soil adsorption nitrogen removal was 9.8%.