Effect of high concentration of organic and inorganic matters in landfill leachate on the treatment of heavy metals in very low concentration level

摘要

Various heavy metals in the landfill leachates were measured up to very low concentration levels of micrograms per litre. Though no violation to Japanese effluent standards was found in respect of individual metal, leachate or treated leachate it still contains higher concentrations of total heavy metals than surrounding water environment. The effluent concentration after treatment was of the same order as raw leachate. Maximum metal solubilities in leachate were calculated taking the presence of inorganic metal complexes into account. Solubilities of metals were high enough and they were not the limiting factor determining concentrations after coagulation. The coagulation with higher pH was not successful in reducing origin metals contrary to the case of pure chemical metals. The heavy metals especially nickel and copper in the leachate were associated with organic matter and consequently they remained in solution unless organic matter was removed. Application of nanofiltration to leachate treatment was studied. It was possible to separate metals from less toxic salts by low retention nanofiltration membranes.