The toxicity and biodegradability of eight main phenolic compounds characteristic to the oil-shale industry wastewaters: A test battery approach

The toxicity of eight phenolic compounds characteristic to the oil-shale in dustry wastewaters was analyzed using a battery of seven microbiotests with species representing different trophic levels (photobacteria, protozoa, cr ustaceans, microalgae). Altogether five monobasic phenolic compounds (pheno l, p-cresol, 2,4-dimethylphenol, 2,3-dimethylphenol, 3,4-dimethylphenol) an d three dibasic phenolic compounds (resorcinol, 5-methylresorcinol, and 2,5 -dimethylresorcinol) were studied. Phenol, 2,4-dimethylphenol, 2,3-dimethyl phenol, and 5-methylresorcinol were classified as "toxic" (lowest 50% letha l (effective) concentration L(E)C-50 of the battery 1-10 mg/L). P-cresol, 3 ,4-dimethylphenol, resorcinol, and 2,5-dimethylresorcinol were classified a s "very toxic" (lowest L(E)C-50 of the battery less than or equal to1 mg/L) . The most sensitive test organisms were crustaceans and/or photobacteria. The toxicity of three different equitoxic mixtures (mixture of all eight ph enols, mixture of five monobasic phenols, and mixture of three dibasic phen ols) was studied using Vibrio fisheri, Daphnia magna, and Thamnocephalus pl atyurus. For all three test organisms the toxicities of individual phenols were proved additive. The efficiency of biotreatment on the toxicity reduct ion of the individual phenolic compounds (2.5 mM) as well as the equimolar mixtures of all eight phenols (1/8*2.5 mM each), five monobasic phenols (1/ 5*2.5 mM each), and three dibasic phenols (1/3*2.5 mM each) was studied usi ng acclimated and nonacclimated activated sludges, in the case of both acti vated sludges phenol, p-cresol, resorcinol, and 5-methylresorcinol were mos t rapidly detoxified. Dimethylphenols and the mixtures had moderate detoxif ication times, while the slowest was the detoxification of 2,5-dimethylreso rcinol and the mixture of resorcinols. Thus, out of eight phenolic compound s studied 2,5-dimethylresorcinol was considered most environmentally hazard ous as very toxic (LC50 for crustaceans 1-5 mg/L) and slowly biodegradababl e. (C) 2000 by John Wiley & Sons, Inc.