Microbial Characteristics And Mechanisms Of Nitrogen Removal On Constructed Rapid Infiltration System

Constructed rapid infiltration system is a new sewage treatment system developed on the basis of the traditional sewage land treatment technology. Controlled sewage is allocated to the performance of a good natural media filtration surface, when sewage downward infiltration of gravity, it is purified as a result of the process of biological oxidation, nitrification, denitrification, filtration, precipitation, oxidation, reduction and other effects. The system has a good removal effect of organic compounds, ammonia nitrogen and SS, but the removal efficiency of total phosphorus and total nitrogen is not ideal.On the basis of making up constructed rapid infiltration system, the paper monitored the various nitrogen concentrations of effluent at different depths, finded out removal and transformation rules. Meanwhile, it studied on microbial characteristics of aerobic stage, facultative stage and anaerobic stage, to explore the mechanisms of nitrogen removal.The system was started by raw water, increasing with hydraulic loading, mainly divided into three periods: prophase (well physical purification), metaphase (instability of effect or biochemical culture) and anaphase (effective biochemical decontamination). At prophase, COD removal mainly dued to physical adsorption; metaphase, as adsorption saturation and slow rate of microorganisms' growth and propagation, COD removal decreased; anaphase, COD removal mainly dued to microbial degradation. The COD removal was mainly concentrated on 80cm above the system; it had better removal efficiency.During stability, monitor and analysis of nitrogen at different depths showed that: (1) ammonia concentration of effluent was 2.9 mg/L, the removal rate as high as 87.3%. (2) nitrite nitrogen concentrations of outlet were relatively low, less impact on the system. (3) nitrate nitrogen concentrations of effluent influent was about 6 times higher than the influent, nitrogen was transformed into nitrate nitrogen, just completing of migration, transformation and degradation, had not been completely removed from the system. (4) total nitrogen had a certain decline, the final concentration of effluent was 13.2 mg/L, the removal rate was 47.8%.The microbial characteristics of the system showed that: (1) qualities of microorganisms at different depths were between 0.0112g/10g fillers and 0.0187g/10g fillers. (2) at the same conditions, the colonies of aerobic medium were the most. Through observation, the volume of aerobic bacteria was largest, followed by denitrifying bacteria, nitrifying bacteria was the smallest. The surfaces of all colonies were moist and smooth. (3) bacteria distribution at different depths:â‘ aerobic stage: aerobic bacteria was the largest, followed by nitrifying bacteria, denitrifying bacteria almost did not exist, the system was mainly of aerobic bacteria;â‘¡facultative stage: the number of aerobic bacteria greatly decreased, and so was nitrifying bacteria, while denitrifying bacteria had a slight increase, the system was still mainly of aerobic bacteria;â‘¢anaerobic stage: aerobic bacteria and nitrifying bacteria almost did not exist, denitrifying bacteria greatly increased; the system was mainly of denitrifying bacteria.Combined with microbial characteristics, the paper studied on the mechanisms of nitrogen removal: nitrogen was mainly removed by biological mechanisms. Ammonia concentration was oxidized through nitrification, and then nitrate nitrogen was reduced into nitrogen by denitrification, and ultimately escaped from the system. Removal of nitrogen mainly depended on nitrification, denitrification, and there may be anaerobic ammonium oxidation. Because of lack of carbon source, the system was inadequate to meet carbon source of denitrification, removal efficiency of total nitrogen needed to be improved.