Authors: KEREM GÜNGÖR, KAHRAMAN ÜNLÜ
Abstract: Bench-scale soil column experiments were performed to examine the effects of soil type and infiltration conditions on the removal efficiencies of wastewater nitrites and nitrates during the biological ripening phase of soil aquifer treatment (SAT) columns. SAT was simulated in three 1-m-high soil columns packed with 3 different natural agricultural soils having sandy clay loam (SCL), loamy sand (LS) and sandy loam (SL) textures. All columns were equipped with tensiometers and soil-water sampling ports, and received secondary effluent from a wastewater treatment plant with a conventional biological treatment system. Soil columns were ponded with wastewater to a depth of 2.5 cm above the soil surface and operated under 2 different alternating wet and dry cycles, 7 days wet/7 days dry and 3 days wet/4 days dry. The effect of wetting and drying periods on SAT nitrogen removal performance was assessed comparing nitrite and nitrate removal rates of 7 days wetting/7 days drying and 3 days wetting/ 4 days drying cycles. Infiltration rate and the length of wetting period were important parameters affecting nitrogen removal efficiency of SAT columns. Denitrification performance of the columns decreased significantly when the infiltration schedule was switched from 7 days wetting/7 days drying to 3 days wetting/4 days drying cycles. LS soil operated with 7 days wetting/7 days drying cycles had the highest (95%) nitrogen removal performance. SCL and SL soils can be operated under both 7 days wetting/7 days drying cycles and 3 days wetting/4 days drying cycles to meet the denitrification/nitrification requirements of SAT.
Keywords: Soil aquifer treatment, Wastewater, Nitrite and nitrate removal
Full Text: PDF