An effective method for decentralized wastewater treatment: addition of polyurethane foam to subsurface wastewater infiltration system

Abstract

Subsurface wastewater infiltration system (SWIS) is widely used in the treatment of wastewater, which is very effective in purification of the sewage and improving its quality, but it is known to be prone to clogging. A laboratory-scale research was therefore proceeded to solve the clogging problem in this study. The experimental results showed that it could significantly enhance the ability of anti-clogging with the addition of polyurethane foam content of 6‰ (mass mixture ratio) to the soil column (R3), which was proved to be the optimum composition and worked successfully with a hydraulic loading less than 26 cm/d for over 4 months. The saturated permeability of the soil columns increased along with the increasing concentration of polyurethane foam. The average removal efficiencies for chemical oxygen demand, NH3–N, TN, and TP were 85, 98, 62, and 99%, respectively, at a hydraulic loading value less than 30 cm/d treated by R3 column. The saturated permeability rate of the control column (R1) was only 1.8 cm/d leading to the clogging after operation of SWIS for 20 weeks, while other three columns (columns 2, 3, and 4 have different packing volumes of polyurethane foam: 3, 6, and 8‰) were not clogged with the saturated permeability rate of 17.3, 46.3, and 84.1 cm/d, respectively.