Study On Degradation Effects Of Phenol In Simulated UCG Wastewater Degradated By Strains

Underground coal gasification(UCG) converts coal into gas fuel or material in underground directly, it has been hailed as "green mining". But the organic pollutants produced in UCG process may contaminate the groundwater, influence the application of UCG. The most substances in organic pollutants are phenolic compounds, primarily include phenol, cresol, xylenol, and so on. Phenolic compounds as protoplasmic poison will produce toxic effects on all living creatures, phenol has been included in the priority pollutants "blacklist" in China, therefore, the degradation of phenolic compounds should be the focus of organic pollutants’ removal in underground coal gasification wastewater.The article takes activated sludge of coking plant and municipal sewage treatment plant as the bacteria source. Taking phenol as the sole carbon source, after domestication and screening, we isolated two high-efficient degradation bacteria:JC and WX. According to physiological and biochemical results of the strains JC and WX, with the analysis of 16 SrDNA sequence alignment, we could identify this two Pseudomonas aeruginosa and Achromobacter xylosoxidans respectively. The optimum environment of JC and WX is: temperature 30~40℃, pH 7, rotation speed 120r/min, inoculation amount 7~16%. When the phenol concentration is 800mg/L, rotation speed is 120r/min, temperature is 40℃, bacteria can grow and reproduct fastest in 40~48h, the bacterial activity is also the highest at this time.Used lignite to simulate gasification processes by tube furnace and UCG simulation platform, collected gas-washing wastewater.Used JC and WX bacteria to degradate the tube furnace gas-washing water.The TOC concentration is 570 mg/L,375.07mg/L and 211.94mg/L respectively, results showed the bacteria work well.The TOC concentration falled from 211.94mg/L to 64.427mg/L and 62.944mg/L in 60 h, the TOC degradation rate were 69.6% and 70.3%. The TOC concentration of the gas-washing wastewater simulated by model test system of UCG was reduced from 1089.19mg/L to 175.07 mg/L after dilution,then used bacteria JC and WX to degradate it, TOC concentration decreased from 175.07 mg/L to 42.01 mg/L、47.44 mg/L after 96 h. Used GC-MS instrument(HP 7890/5975) to analysis the composition and content of orgnic pollutants in the wastewater. Phenol, o-cresol and m-cresol were not found after degradation which were the most organic pollutants in the raw water. Therefore, phenol-degrading bacteria JC and WX had good degradation effects on the removing of phenol and other phenolic compounds in the wastewater simulated by UCG platform.Alkanes, olefins and other small molecule hydrocarbon compounds were found in the wastewater after degradation, maybe the degradation of phenol and other large molecules organic matter was step by step: big molecular substances were decomposed into small molecules at first and then small molecular organics were degradated.