Characterization of organic contaminants present in coal slurry wastewaters

The qualitative and quantitative occurrence and fate of dissolved organic carbon (DOC) leaching into coal slurry transport waters was examined in laboratory generated coal slurries and wastewaters from the Black Mesa coal slurry pipeline. Laboratory slurries were formulated with both western coals (Wyodak, Montana Rosebud and Black Mesa) and eastern coals (Illinois #6 and Pittsburgh #8). The influence of selected physical/chemical parameters on the leaching of DOC material into slurry transport waters was examined. Slurry pH alteration, transport medium, slurry heating and coal storage age were all found to significantly affect slurry wastewater DOC loads.

Qualitative analysis of selected wastewaters demonstrated that the majority of organic compounds present in laboratory formulated coal slurry wastewaters were lower molecular weight species, < 1,000 MW. Fulvic acids represented 31 to 64% of the wastewater DOC loads for laboratory and pipeline generated slurry wastewaters. Oxidation and subsequent derivatization of slurry wastewater organic compounds produced five distinct compound classes, the most predominant being benzenecarboxylic acid and aliphatic dibasic acid esters.

Chlorination of coal slurry wastewaters produced substantial quantities of trihalomethane (THM). Primary THM precursors present in slurry wastewaters were coal derived fulvic acids. An analysis of chlorinated and non-chlorinated coal slurry wastewaters for the presence of mutagenic agents as determined by the Ames assay demonstrated an absence of mutagenic activity in these samples.