Changes in characteristics of soils at 50-centimeter depth after passing with domestic wastewater in horizontal direction

Abstract

This study was to determine the potential of removal of cations, anions and E. coli in domestic wastewaters by 4 types of soil, namely, Pak Chong (Pc), Khamphaeng Saen (Ks), Muak Lek (Ml) and Ban Bung (Bb). The soil samples were specifically taken at 50 cm depth from ground surface. The wastewater was allowed to seep through the 60 cm long PVC soil column in horizontal direction for a period of 140 days. The study revealed that the loamy-sand type allowed the highest percolation. Nevertheless, the wastewater could flow freely through the column of all soil series within 140 days without any clogging problem. Khamphaeng Saen, Pak Chong, Muak Lek and Ban Bung soil series entirely removed E. coli after 6, 14, 15 and 16 weeks of treatment, respectively. All soil series could reduce COD, orthophosphate, NH4-N, Na, Mg, Cl and SO4, except the fixed-form of K ion which was leached later. For Khamphaeng Saen soil, K, Na and Mg in exchangeable form were more leached than those by other soil samples. The Ban Bung, Muak Lek and Pak Chong soil series maintained the aerobic condition after 2, 3 and 4 weeks of wastewater treatment, respectively. This was evidenced by the nitrification process in the test column. After the experiment, the soil pH was slightly increased. This was due to the enhanced level of exchangeable cationic pollutants in the soil. In addition, total-P, total Kjedahl nitrogen, exchangeable K, Na and soluble SO4 and Cl were significanty increased while available-P, NH4-N, organic carbon and CEC were slightly increased. However, Mg ion in Khamphaeng Saen soil series was released after passing of domestic wastewater. In addition the movement of ions and E. coli depend on soil permeability. This study indicated that Khamphaeng Saen soil could filtrate most ions and E. coli at 0-5 cm whereas Bang Bung soil accumulated at 30-60 cm of soil column.