Measurement and evaluation of pollutants in landfill leachate.

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We investigated the leachates from three solid waste disposal sites for several times. Various heavy metals in the landfill leachates were measured up to very low concentration level of microgram per liter. Though no violation to Japanese effluent standard was found in respect of individual metal, leachate or treated leachate still contains higher concentration of total heavy metals than surrounding water enviromment. The effluent concentration after treatment was of the same order of raw leachate. Maximum metal solubilities in leachate were calculated taking the presence of inorganic metal complexes into account. Solubilities of metals were enough high and they were not the limiting factor determining concentrations after coagulation. The coagulation with higher pH was not successful in reducing concentration of leachate-origin-metals contrary to the case of pure chemical metals. The heavy metals especially nickel and copper in the leachate were associated with organic matters and consequently they remained in solution unless organic matters were removed. Application of nanofiltration to leachate treatment was studied. It was possible to separate metals from less toxic salts by low retention nanofiltration membranes.We also measured organic micropollutants by GC/MS.Plastic additives were detected at every site. Less hydrophobic compounds with low octanol-water partition coefficient were decreased in concentration with time elapsed from disposal. High level of disinfection by-products formation potential was detected in leachate. The treatment process of landfill leachate was very effective for plastic additives but not effective for disinfection by-products formation potential.