Main Article Content
Abstract
Based on a large number of experimental data, this paper puts forward a three-stage hypothesis of biochemical degradation of coking wastewater. And studies on the biochemical degradation kinetics in various stages through laboratory experiments have been made. In these studies, a new concept has been proposed, that of substances present in coking wastewater that can be biochemically treated to produce ammonia nitrogen. And this class of substances, we define and call BN for short. BN’s meaning is to produce ammonia nitrogen in the process of biochemical treatment. The relationship between COD, the substances that can biotreatedly produce ammonia nitrogen (BN), ammonia nitrogen and time in biochemical degradation is revealed. In the first stage of biochemistry is the removal of a large amount of organic pollutants, so that the strong smell of the wastewater is removed while most of the COD is removed. In the second stage of biochemistry is the removal of substances that produce ammonia nitrogen (BN). These increases the ammonia nitrogen in the wastewater. In the third stage of biochemistry is degradation of ammonia nitrogen, so that ammonia nitrogen meets the emission standard. The mathematical model of biochemical degradation kinetics is proposed. The mathematical model consists of 12 formulas. The first stage has one formula, the second stage has five formulas, and the third stage has six formulas. The hydraulic retention time of biochemical treatment tank at different stages can be calculated by these formulas. Based on the proposed mathematical model, this paper illustrates the significance of the three-stage theory to the design and operation of the biochemical treatment of coking wastewater. At the same time, we can see the importance of the new concept of BN.