Bioaugmentation Of Biological Contact Oxidation Technology For Coal Gasification Wastewater Treatment

Due to the supply gap and rising price of natural gas, coal gasification industry plays an important role in renewable energy system. However, coal gasification industry is still in demonstration phase. Thus, coal gasification wastewater(CGW) treatment was still a serious problem, which hinders the development of coal gasification industry. CGW from China Coal Longhua Harbin Coal Chemical Industry Co. Ltd., contains large amout of refractory compounds, such as phenolic compounds, polycyclic aromatic hydrocarbons and heterocyclic compounds. These refractory compounds could not be removed sufficiently in biological wastewater treatment system. In order to meet the discharge standard, a large amount of medicament agent were consumpted in coagulated deposition system. According to operation data in site, biological contact oxidation system was the crucial unit for organic compounds removal. Thus, bioaugmentation technology was adopted in this research.Phenol degrading bacteria with inducers release ability were isolated based on conventional isolation method and quorum sensing theory. Three phenol degrading bacteria FF1, FF2 and FF3 isolated from biological contact oxidation system, were characterized as Stenotrophomonas sp., Klebsiella sp. and Enterobacter sp.. The optimum complex proportion of FF1, FF2 and FF3 was 1: 1: 1. Phenol degrading agent(PDA) constructed by FF1, FF2 and FF3 could resistant to phenol of 733.4mg/L. The optimum inoculation dosage of PDA was 5.0‰.Based on the research of phenol degrading ability and inducers release ability, performence of biological contact oxidation system bioaugmented with PDA was investigated. In the experiment of laboratory scale, effiectiveness of biological contact oxidation system bioaugmented with PDA was investigated by sequencing batch biofilm reactor. According to the results in laboratory scale, organic compounds, total phenol and NH3-N removal before and after bioaugmentation were increased from 81.0% to 87.0%, from 76.2% to 89.4%, from 22.4% to 36.2%, respectively. The performance of biological contact oxidation system bioaugmented with PDA in summer was better than in winter. p H in the range of 6.0 to 8.0 and dissolved oxygen in the range of 0.5 to 5.5mg/L would not affect organic compounds, total phenol and NH3-N removal. The pilot plant was designed according to biological contact oxidation system in China Coal Longhua Harbin Coal Chemical Industry Co. Ltd.. In the experiment of pilot scale, effieciency of biological contact oxidation system bioaugmented with PDA was investigated. According to the results in pilot scale, organic compounds, total phenol and NH3-N removal before and after bioaugmentation were increased from 58.1% to 78.2%, from 66.0% to 80.0%, from 5.1% to 25.1%, respectively. Biological contact oxidation system bioaugmented with PDA could resistant to 350~3 000mg/L total phenol of CGW.Bioaugmentaion mechanism of PDA was discussed by investigating the effect of phenol degrading agent and its inducers on pollutions removal, enzyme activity, inducers release ability and microorganism diversity. The results showed that phenol degrading ability of PDA was not the only resean for the improvement of total phenol removal. Moreover, inducers released by PDA which increased C12 O and C23 O activity and speeded up ring opening was the main reason for the improvement of total phenol removal. Due to the improvement of microorganism composition and capability, other organic compounds removal was increased, which was also the reason for NH3-N removal enhancement.The research of PDA in this paper was applied in China Coal Longhua Harbin Coal Chemical Industry Co. Ltd.. Organic compounds, total phenol and NH3-N removal before and after bioaugmentation were increased from 78.5% to 82.3%, from 80.0% to 86.6%, from 25.1% to 27.3%, respectively. The consumption of medicament agent in coagulated deposition system was significantly reduced.In summary, the research of biological contact oxidation system bioaugmented with PDA expanded the basic theory of CGW treatment, which was significant for CGW treatment plant saving cost and meeting the discharge standard.