Denitrification intensified of compound mixed subsurface wastewater infiltration system

Abstract:

In order to improve the hydraulic permeability and intensify denitrification of subsurface wastewater infiltration system, one apparatus was established in a pilot laboratory with the mediums of 55% cinder, 25% soil and 20% grass carbon mixed completely. The apparatus was dosed 4 times daily with domestic wastewater at 10 cm•d-1. Operating conditions were changed in order to improve the removal efficiency of TN. The average removal efficiency of COD, NH4+-N, TN were 73.3%, 98.2%, 20.1%, respectively, when outlet location was at normal position; The average removal efficiency of COD, NH4+-N, TN were obtained 75.4%, 79.1%, 26.9%, respectively, When outlet location was heightened 30 cm, the bottom of apparatus was submerged so that anaerobic environment was formed; The average removal efficiency of COD, NH4+-N, TN were obtained 88.9%, 88.5%, 55.7%, respectively, when the apparatus was conducted in glucose added in domestic wastewater. The results showed that the removal of TN was not been improved by adding grass carbon in apparatus; outlet location raised could increased TN removal efficiency from 20.1% to 26.9%, but the action was limited; the glucose added could increased TN removal efficiency from 26.9% to 55.7%, and TN concentration of effluent decreased from 22.8 mg•L-1 to 14.2 mg•L-1; at the same time, the removal of COD, NH4+-N had not been affected. So the critical factor of the TN removal blocked was carbon absent.