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.
Highlights
Coke is an important raw material in steel production, which is an ideal fuel and reducing agent
The results showed that the average removal rate of COD increased by 18% compared to the activated sludge system by adding sludge bacteria agent; PCR-DGGE results showed that the kind of microbes in the biochemical system became more abundant, the varieties of microorganisms varied from 14 to 23 [6]
The results show that the biotreatedly produce ammonia nitrogen (BN) began to degrade after 2 days, biochemical degradation of phenolics affected the BN, ammonia nitrogen began to degrade after 2 days, that phenolics affected the biochemical degradation of ammonia nitrogen
Summary
Coke is an important raw material in steel production, which is an ideal fuel and reducing agent. In the analysis and detection of the components of coal processing wastewater, Lingdong Kong et al discussed 244 kinds of organic pollutants by GC/MS. There were a small amount of alcohol, aldehydes, acids, vinegar, aromatic hydrocarbons such as fluoranthrene, pyrene, and naphthacene, benz [c] anthracene, benzophenanthrene, benzo [j] fluoranthene, benzoapyrene and so on [2]. Degradation of these pollutants mainly adopts the kind of biochemical treatment process. Biochemical treatment is the use of microbial metabolism to make waste organic pollutants in the water into CO2, water and other harmless substances to realize wastewater purification [3]. The results showed that the average removal rate of COD increased by 18% compared to the activated sludge system by adding sludge bacteria agent; PCR-DGGE results showed that the kind of microbes in the biochemical system became more abundant, the varieties of microorganisms varied from 14 to 23 [6]
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