Removal of Pollutants From Soil Infiltration Systems

Hydraulic load, organic load and the C/N ratio are main factors affecting nutritive salt removal efficiency of wastewater soil infiltration systems. In a laboratory with controlled temperature, effects of hydraulic load, organic load and environmental conditions on pollutants removal efficiency of soil infiltration systems were analyzed. Results show that when hydraulic load was lower than 0.15 m³•m^-2•d^-1, removal efficiencies of COD_Cr, TN and P in simulated domestic sewage reached over 84%, 37% and 93%, respectively, meanwhile the number of Nitrosomonas was up to 4.50×10⁶ per gram dry soil. The perched water in the upper layer of the installation did not affect much the removal efficiencies of COD_Cr, and phosphates. However, as a result of lowered dissolved oxygen in the system, nitrification of ammonia nitrogen was inhibited and the removal efficiency of ammonia nitrogen and TN lowered. Under the condition of enough DO, higher C/N ratio (5:1) was conducive to TN removal efficiency in the system.