The biological treatment of carbonization effluents—IV

Abstract

Abstract Biological systems operating the continuous, completely mixed activated-sludge process have been employed to investigate the further benefits obtained from the addition of certain biochemical factors such as p-aminobenzoic acid and glucose, which have been shown to have a significant effect on the rates of removal of constituents of coke-oven wastes such as thiocyanate and cyanide. These “growth factors” have now been shown to encourage the oxidation of ammonia, not only in non-bactericidal wastes, but also in the biological treatment of coke-oven effluents. The results of the investigation show that, in addition to the normal maintenance of neutral conditions in the aeration tank, acidification of a limed liquor before biological treatment, greatly reduces the deposition of calcium compounds in the bacterial sludge. This procedure can enable increases to be made in the organic loadings applied to such systems, with the added likelihood of additional benefits from growth factor application. It has been shown that, if the influent ammonia concentration during this modified treatment of a limed coke-oven waste can be reduced to 100–200 mg 1−1 by efficient operation of the lime still, it may be possible to oxidize the ammonia to nitrate, without any additional aeration stage. Yet another property of glucose and other growth factors is their ability to promote the biochemical oxidation of organic bases such as pyridine, the latter normally being regarded as resistant to bacterial breakdown. Experimental evidence suggests that, when once a particular breakdown pathway has been established, the continued application of an organic additive may not always be necessary.