It has been shown under laboratory conditions that it is possible to produce and utilize the alkali (alkalinity) for the nitrification of fixed ammonia nitrogen contained in sewage waters of byproduct coke plants with the biological denitrification of the additionally added amount of nitrites and/or nitrates at the pretreatment stage which precedes the single-phase nitrification-denitrification stage.Denitrifying bacteria, while being facultatively anaerobic, can oxidize, under high-load conditions characteristic for the equalizing preaeration tank, organic contaminants contained in effluents of byproduct coke plants not only by air oxygen but also by the bound oxygen of nitrites and nitrates specially added to sewage water in the form of their salts.The possibility of producing the alkali by addition of nitrites and nitrates to the water is limited and depends on the ratio of the initial COD to the initial content of fixed ammonia, which is called here the denitrifying capacity (DC) of sewage waters.The alkali produced upon biological denitrification of nitrites or nitrates may serve as a fully satisfactory replacement for conventional alkaline reagents used in the ND technology.The results obtained also make it possible to come to the conclusion concerning the expediency of the combined purification of liquid effluents of byproduct coke plants and the sewage of plants with the content of nitrites and/or nitrates within the range of the reserve of the denitrifying capacity of the former [4].This makes it possible not only to reduce the consumption of air (power consumption) at the pretreatment stage but also to rule out or reduce, depending on the content of nitrites and/or nitrates, the consumption of conventional alkaline reagents in the technology of denitrification of sewage waters of byproduct coke plants and, hence, to reduce the general expenses on their purification. The sewage waters of interest in this respect (in our opinion) include the effluents of the "Azot" plant (Cherepovets) provided that they are treated in the nitrification regime.
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