Abstract
Removal efficiencies of Simazin, Fenitrothion, Napropamid, and tetrachloroethylene, PCE, from synthetic wastewater by the multi-soil-layering, MSL, method were studied. Volcanic ash soil (Kuroboku) was generally more effective than sandy soil (Masa) for removal of pesticides. Fenitrothion could be effectively removed by even sandy soil only or zeolite only. Addition of 2 weight % of activated carbon to an MSL system using volcanic ash soil significantly improved its performance for Simazin, Napropamid and PCE removal. Removal efficiencies of the above-mentioned toxic chemicals from wastewater containing mean concentrations (μg·l-1) of 350 for Simazin, 800-1300 for Fenitrothion, 2000-3500 for Napropamid, and 140 for PCE were 73-100%, 95-97%, 71-100%, and 95-99%, respectively, at their steady state with the loading rates of 270-400 l·m-2·day-1. In terms of PCE removal, an MSL system using sandy soil with the addition of metal iron also showed a high removal efficiency of more than 90%. In this MSL system and that with added activated carbon at the rate of 0.2 weight %, PCE was removed not only by sorption but also by degradation. Chemical degradation by metal iron added to the MSL system and biodegradation of PCE into TCE and cis-1,2DCE seemed to occur simultaneously.
