Study On Sewage Nitrogen Removal With Constructed Rapid Infiltration In Three-Gorges Region

Constructed rapid infiltration (CRI) system is one type of land-treatment technologies. The characteristics of CRI system are high hydraulic loading and less land area, which is stemmed from the applicability of fast infiltration media replaced the natural soil. From previous experiment, it concludes that the low nitrogen removal rate counteracted CRI system run. This article emphatically discusses the nitrogen removal performance of CRI system with the factors of the wet/dry ratio, hydraulic loading cycle, carbon/nitrogen ratio, and the construction of equipment.The prior preparatory experiments would deal with the circumstance of soil oxidation-reduction changed by running parameters. This study result applied reliably data for constructing next experiments device.In the wet/dry (W/D) ratio and hydraulic loading cycle (HLC) testing, research respectively discusses under the condition of W/D ration as 1:1,1:3,1:9, the nitrogen removal performance of three kinds of HLC as 12h,24h,48h. The results indicate that smaller W/D ratio brings effective nitrogen removal. For NH3-N removal, smaller W/D ratio and shorter HLC bring effective result. Lengthen HLC can decrease the effluent NO3-N concentration.In the carbon/nitrogen ratio testing, influent TN concentration keeps the range of 55~65mg/L. The results indicate that increased the amount of carbon brings effective TN removal. The NH3-N removal reactivity mainly finish in 0.6m depth soil, and 1m depth soil is available for wastewater treatment. The NO3-N removal can be improved clearly by increased the amount of carbon, which is show that denitrification could be intensified by increasing carbon.Through the construction of equipment testing, under the condition of soil/sand vol. ratio 3:1 research discusses the nitrogen removal performance of four depth as 0.3m,0.6m,1.0m,1.5m respectively. The results show that the surface 0.6m contributes great for the COD and NH3-N removal, while the 1.0m is most suitable for TN removal. Under the condition of 1.5m depth, research discusses the nitrogen removal performance of three soil/sand vol. ratio as 2:1,3:1,4:1 respectively. The results show that bigger soil/sand vol. ratio bring effective nitrogen removal result. Soil/sand vol. ratio 4:1 have maximal NH3-N, NO3-N and TN removal rates. Meanwhile, the bigger soil/sand vol. ratio lessen the infiltration coefficient. So building CRI setting need to take influent TN concentration and treatment hydraulic loading into account, in this way suitable soil/sand vol. ratio could be selected.