Rapid Removal Of Organic Pollutants In Coal Gasification Wastewater By Using Halophilic Microorganisms

Coal gasification wastewater is a typical high-concentration,high-pollution,toxic and refractory organic wastewater with high salinity.The existing pretreatment methods are mainly physical and chemical methods,which have problems such as high energy consumption,secondary pollution and unsatisfactory pretreatment effects.In the previous studies,some halophilic microorganisms were found with the efficient flocculation ability for the organic pollutants of coal gasification wastewater.So the osmotic-tolerant halophilic bacteria are as the research object separated from the crystallization pool in this study.The analysis of isolation,identification and characteristics are carried out on the efficient strains,and the correlation study is performed between the release of compatible solutes and the pretreatment effect of coal gasification wastewater in order to provide a theoretical basis for the application of halophilic bacteria in pretreatment of coal gas wastewater.The osmotic-tolerant mixed flora from the crystallization pool of solar saltern is obtained through osmotic enrichment culture.58 strains are isolated and purified,and three representative strains among these strains are selected for the further analysis.The three strains of TG-4,TG-5 and TG-20 are identified as Pseudomonas stutzeri,Salicola marasensis and Halorubrum litoreum by the morphological observation and 16S rDNA sequence analysis,respectively.The osmotic-tolerant mixed flora and strains of TG-4,TG-5 and TG-20 have good pretreatment effect for coal gasification wastewater.After pretreatment,the COD removal rate and COD value of coal gasification wastewater reached 86-90%and 2013-3202 mg/L,respectively;the removal rate and value of volatile phenol reached 64-78%and 94-156 mg/L,respectively.The above value of COD and volatile phenol can meet the requirements of operation load in biochemical treatment process.The correlation of efficient flocculation for halophilic microorganisms with organic pollutants and the rapid release of intracellular compatible solutes is found by comparative analysis of the compatible solute and the wastewater pretreatment effect.The growth conditions optimization of S.marasensis TG-5 is used by the single factor analysis.The optimal culture conditions were the temperature of 40?,the pH value of 7.0,the inoculation amount of 7%and the salinity of 15%,indicating that the bacterial strain is moderate halophilic bacteria with the characteristics of acid and high-temperature tolerance.The growth of strain TG-5 could reach the stable period after 48 h culture,and the biomass accumulation was higher than L60.With the increase of culture salinity,the accumulation of intracellular compatible solutes increased,and the instantaneous release rate of compatible solutes increased with the increase of environmental osmotic pressure difference.The effect of culture salinity on the pretreatment of coal gasification wastewater by bacterial cells was not significant.When the culture salinity was 15%-30%,the bacterial cells had good flocculation effect on the pretreatment of coal gasification wastewater,but the flocculation particles and sedimentation time are both different.Different components of bacteria pretreatment coal gasification wastewater,only small flocculation particles appear and the pretreatment effect is poor.These indicate that the flocculation is due to the interaction of the components.Above all,the flocculation mechanism of halophilic microorganism with organic pollutants in coal gasification wastewater may be that the compatible solute circles form around the cells when the strain cells are in a low permeability condition of the wastewater salinity and make instantaneous release of compatible solutes.According to the principle of similarity compatibility,hydrocarbons,volatile phenol and other organic matters in wastewater gathered around the cells with the formation of hydrophobic surface.Then the similar hydrophobic balls gathered themselves together,form large flocculation particles and rapidly precipitate under their own gravity.