ENVIRONMENTAL IMPLICATIONS 



167 



TABLE 2 



CONCENTRATIONS AND WASTE-WATER TREATMENT 



EFFICIENCIES OF MAJOR CONSTITUENTS OF 



COAL-CONVERSION EFFLUENTS* 



*Adapted from Herbes, Southvi^orth, and Gehrs, 1977. 



Identities of classes and their anticipated levels in untreated and 

 treated wastes are given in Table 2. Phenols will be the predominant 

 class of chemicals present in the untreated effluents, with levels as 

 high as 6000 mg/liter being measured (Wender, 1975). Chemical 

 stripping of most of the phenolics (to retrieve them for use as 

 chemical feedstocks) will be followed by biological treatment, which 

 will reduce levels to <1 mg/liter. Concentrations of unsubstituted 

 aromatic hydrocarbons present in untreated waste waters will be 

 hmited primarily by water solubility, with the higher molecular 

 weight polycyclic aromatic hydrocarbons constituting lesser 

 amounts. Microbial degradation rates of aromatic hydrocarbons are 

 inversely related to molecular weight as reflected in the estimated 

 removal efficiencies of 90+% and 30 to 80% for monoaromatic and 

 polycyclic aromatic hydrocarbons, respectively (Table 2). In- 

 corporating nitrogen (aromatic amines) or sulfur (thiophenes) into 

 the basic aromatic ring structure tends to increase solubility and 

 decrease microbial degradation rates as compared with unsubstituted 

 aromatics. Thus these two classes of compounds are expected to 

 comprise a significant percentage of the total organics contained in 

 treated, aqueous, coal-conversion effluents. 



POTENTIAL TOXICITY OF COAL- 

 CONVERSIOIM EFFLUEIMT CLASSES 



The toxicity of phenolics to aquatic life is better defined and 

 understood than is the toxicity of other organic classes expected to 



