Decontamination of landfill leachate by soil infiltration.

A soil column study was conducted to evaluate the efficiency of soil to attenuate pollutantsin landfill leachate.It was found that more than 60% of the initial alkalinity,COD,and totalnitrogen was removed after the leachate had percolated through the soil column.Lower effi-ciencies were observed for the removal of dissolved cations,ammonia nitrogen,and nitratenitrogen.When previously percolated leachate was recirculated through the soil column,sig-nificant removal(93.6%)of ammonia nitrogen was achieved.Moreover,a further reduction inCOD,total nitrogen,nitrate nitrogen,and potassium was evident.Bioassay tests of seed germi-nation and root growth of Brassica chinensis were performed to compare the phytotoxicitiesof untreated,percolated,and recirculated leachates.The phytotoxicity was reduced by bothtreatments,with the greatest detoxification observed in the leachate recirculation treatment.Thevalues ofpH and Olsen phosphorus were significantly reduced(P<0.01)in the treated columnsoil.whereas significant increases(P<0.05)in electrical conductivity(EC),various forms ofnitrogen,exchangeable sodium percentage(ESP),potassium,magnesium,zinc,and iron wereobserved.EC,ESP,potassium,magnesium,sodium,iron,and various forms of nitrogen accu-mulated at the soil surface(10 cm).On the other hand,manganese was deposited at 20 to 50cm below the soil surface of the treated column.1989 Academic Press.Inc.