38 



sludge to acclimate to oxiuation of a higher concentration of 

 tetrachlorocatechol than normally present in bleach waste or, 

 possibly, to tetrachlorocatechol xtself. In either case, the 

 salient point is that chlorinated catechols apparently can be 

 oxiaizecl, and by proper design and operation, any one of a number 

 of biological treatment systems vith detention times ranging from 

 hours to days could remove thorn. 



AS noted in the Il/i'iiDJUCTIOI;, tho primary reason for studying 

 toxicity of di- ana tetraclilorocatechol \;as the export opinion that 

 they \.;ere likely constituents ox bleach waste, xxapson ana Anderson 

 (1966) suggesteu tiiat chlorinateo. phenols loay represent some 

 fraction of the organically bounu chlorine in bleach waste. 

 Therefore, there is reason tc assume; that chlorinate- 1 phenols as 

 well as catechols may be present m bleach waste. Consequently the 

 results reported herein rogaramg toxicity of di- and 

 tetrachlorophenol (1.6 and 1,8 times as toxic, respectively, as 

 the corrcsponcdng chlorinated catechol) take on added significance 

 in consideration of bleach v;aste toxicity. 



Laboratory results reported by .tapson ana Anderson (1966) showed 

 that substitution of some chlorine .iioxiue for chlorine during the 

 first stage of pulp bleaching significantly reduced the amount of 

 organically boun . clilorine m the waste waters, in other words, 

 toxicants such as chlorinated catechols and phenols might be 

 eliminated by altering the bleaching process. Betts and U'ilson 

 (1966) have confirmed that substitution of chlorine dioxide for 

 some chlorine during bleacning significantly reduced toxicity of 

 bleach wastes. The use of chlorine dioxiae in bleaching may 

 become more significant xn th. future due to technical aevelopments . 

 However, for the present it appears that biological treatment will 

 have to be relieu upon to elii^nnate acute toxicity eauscu by orgaiiic 

 compounus in bleach waste. 



