Adsorbable organic halides ( AOX ) , AOX formation potential , and PCDDs / DFs in landfill leachate and their removal in water treatment processes

Adsorbable organic halides (AOX) and AOX formation potential (AOXFP) were investigated in 46 landfill lea-chates as potentially toxic parameters. AOX in landfill leachate was within the range <10–2200 mg Cl/l, and AOXFP was within 51–15 000 mg Cl/l. AOX and AOXFP correlated with chemical oxygen demand (COD).AOX discharge from closed landfills was generally lower than that from operating landfills. The molar ratio of AOXFP/total organic carbon (TOC) suggested that organic compounds in a leachate have a double bond every 15–190 carbons under the supposition that one chlorine would add to one double bond. The five landfills discharging high-level AOXFP (>4000 mg Cl/l) were all landfills where sludge had been dumped. The removal efficiencies of three parameters through leachate treatment processes were as follows: poly-chlorinated dibenzo-dioxins/dibenzo-furans (PCDDs/DFs) > TOC > AOX. PCDDs/DFs were substantially removed at p.p.t. levels, while AOX was hardly removed at relatively low levels.