QUANTITATIVE ASSESSMENT OF NATURAL PURIFICATION IN WETLAND FOR LINEAR ALKYLBENZENESULFONATES

Natural purification in a small wetland (474 m2) for linear alkylbenzenesulfonates (LAS) was assessed quantitatively and was found to involve adsorption on sediment particles and degradation with bacteria in the wetland. Temperature affected the amount of biodegradation but not adsorption. Consequently, biodegradation did not occur and LAS was decreased only by adsorption in winter in the present wetland. In the summer, decrease by biodegradation was larger than that of LAS in the inflow, and thus, LAS already adsorbed was also decreased. Natural purification is discussed from the standpoint of the carrying capacity of adsorption or biodegradation calculated from field data. It was concluded that the wetland could adsorb about 5 kg of LAS and could remove more than 20 kg of the chemical in a year while about 35 kg of LAS inflowed in a year.