The implementation of the two-phase (nitrificator-denitrificator) technology of biochemical purification of wastewaters of the byproduct coke section of the Severstal plant from nitrogen in the newly built third stage of the biochemical installation made it possible to substantially improve the quality of the plant effluents sent for additional purification to city sewage works in order to remove not only ammonia nitrogen but also other specific contaminants (1). Since the design volume of additional units of the biochemical installation (BC1) was realized by about 70 percent at the time of startup and adjustment operations the volume of wastewaters purified in the nitrification-denitrification regime was about 180-300 m~3/hr with the volume of their formation being 250-300 m~3/hr. This did not make it possible to achieve sufficiently rigorous (30 mg/liter) standards, as compared with those realized (ca. 60-70 mg/liter), with respect to the content of residual ammonia nitrogen in the effluents from byproduct coke production, which were established by environmental protection organizations. The solution of this problem prior to the completion of the construction of additional units of the biochemical installation seemed to be possible due to the implementation, in its second stage, of a single-phase technology of nitrification-denitrification of sewage, which is more efficient than the two-phase technology (2).
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