Treatability and Assessment of Coal Conversion Wastewaters

University of North Carolina at Chapel Hill, 9/1/78-8/31/80

Investigators: Singer, Lamb, Pfaender, Goodman, Reckhow, Speitel, Rader, Marshall

The objectives of this research were to assess the environmental impact of wastewaters originating from the production of synthetic fuels from coal and to evaluate various technologies for the treatment of these wastewaters. The major focus was on aerobic biological treatment which wais projected to be the principal means of removing organic impurities from these wastewaters and a cornerstone of any overall wastewater treatment program.

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Additional Background: A synthetic wastewater, designed to simulate a real conversion process wastewater, was formulated and fed to a series of aerobic biological reactors. In addition to TOC, BOD, and COD data, the treated wastewaters were analyzed with respect to their phenolic content and the presence of residual organics using chromatographic techniques. Aquatic bioassays and mammalian cytotoxicity tests were performed on the raw and treated wastewaters to evaluate their potential environmental impact.
Experimental results from Phase I of the project, included coagulation, adsorption, and preliminary biological treatability studies. Model studies, using a simulated coal conversion wastewater at 25% of full strength, suggest that coal conversion wastewaters are biologically treatable via aerobic treatment processes; phenol is completely removed by biological systems with sludge ages greater than 5 days. Preliminary aquatic bioassay experiments and cytotoxicity bioassays showed that the toxicity of the wastewater was substantially reduced following biological treatment and that the reduction in toxicity increased with increasing sludge age. The adsorbability of the residual organics following biological treatment on activated carbon was found to decrease with increasing sludge age. Acidification and coagulation studies indicated that tar can be effectively precipitated and removed from coal conversion wastewaters by acidification to pH 4.5 to 5.0; coagulation using alum appears to be an ineffective means of removing tar from these wastewaters.



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