Study On Microorganisms Agent For Refractory Organic Wastewater Treatment

Reference to the analysis of water quality data for the majority of refinery wastewater in journals, and according to the composition and content of various organic compounds of the refinery wastewater, the refinery wastewater main contains alkane, hydrocarbons, aromatic categories. substituted aromatic compounds, phenols and other types of refractory organic pollutants.High concentrated refractory organic- aromatic, is selected to represent as a goal of this study, aimed to give some certain simulated research for the treatment of wastewater containing aromatics in laboratory-scale. The effect of the method-microorganisms agent, which is appropriate for the treatment of the wastewater, is investigated, which providing some operation reference for the treatment of refractory organic wastewater in refinery wastewater treatment plant. Based on such pollutants as a target degradation products, screening against refractory pollutant- high-efficiency degrading bacteria. Characters of all the bacteria and its degradation rate of the corresponding organic pollutants is investigated. In order to verify the function of microorganisms agent and the effect of bioaugmentation technology, one degrading bacteria which has relatively better performance in degrading capacity is choosed, respectively, to form microorganisms agent, exogenous bacteria were inoculated to a sequencing batch reactor to treat wastewater containing aromatic mixture. Through my own assembly test reactor, two tests were conducted over two months of tracking tests, respectively, and the result has some certain reference.The study selected Toluene(called T), Ethylbenzene(called E), p-Xylene(called X), Benzothiazole(called T), Dibutylphthalate(called B) and 2-Methylpyridine (called P) of aromatic (for convenience, referred TEXTBP in the paper) as the research goal of the paper. In view of the above six pollutants, several bacteria were screened in solid and liquid screening media through preliminary screening. Through observing in electric microscope, they are bacilliform and orbicular. When cultured to log growth phase after one day time, degrading bacteria of ethylbenzene and pyridine are orange, the others are light white in color. And optical density(OD)grow to maximum, 5 on the average, pH also increase from 7 to 8-9.Through flask degradation experiment and chromatographic analysis, and after several rounds of determination, two strains of the degrading bacteria were choosed to determine the performance of degradation of organic pollutants. The values of degradation rate and degradation percent represent as the extent of substrate degradation, and the extent of substrate degradation represent as the degradation performance of the bacteria. Results showed that, the degradation percent of Toluene and Ethylbenzene can both reach 100% in 17 hours, the degradation rate can achieve to 0.127mg/A·h, 0.073mg/A·h, respectively.The degradation percent of 2-Methylpyridine is 75% in 17 hours, the degradation rate is 0.127mg/A·h. The values of degradation rate and degradation percent of Benzothiazole is 31% and 0.063mg/A·h in 17 hours. In 24 hours the two values of Dibutylphthalate can get to 53% and 0.028mg/A·h, p-Xylene can get to 38% and 0.089mg/A·h within 22h.According to the growth and degradation capability of the bacteria, the best five strains, which corresponding to toluene, ethylbenzene, p-xylene, and 2-benzothiazolyl and the five numerical values were identified by the Institute of Microbiology of the Chinese Academy of Sciences. They are Bacillus megaterium, Staphylococcus xylosus, Bacillus sphaericus, Pseudomonas nitroreducens and Staphylococcus xylosus in species, and had been collected in the institute. Named B.megaterium J1, S.xylosus Y1, B. sphaericus 2J1, P.nitroreducens S1 and S.xylosus B1, respectively. The strain which had better degradating performance corresponding to dibutylphthalate summarized above, was named L1 for research and writing convenience.When the effluent quality results expressed in the form of COD using dichromate method, pyridine is difficult to oxidize in acidic potassium dichromate conditions, and the oxidation rate is very low. So 2-methylpyridine will not be added in the simulated refinery wastewater, and only sewage containing TEXTB would be treated in the paper.The sewage containing TEXTB treated by conventional activated sludge method, the effect is not so good. In order to improve the performance of the system treating sewage containing refractory organic, treatment system was amended improved by microorganisms agent in the same condition.Specialized degrading bacteria including B.megaterium J1, S.xylosus Y1, B. sphaericus 2J1, P.nitroreducens S1 and L1 were cultured to log growth phase, bacterial suspension were mixed by 1:1 ratio and centrifugal later, getting 1g wet soil bacteria by adding 100mL mineral salt additived as aid agent, then coat on plate for colony counting. The viable cell counts per gram were3.6×107CFU/g, 5.2×107CFU/g, 4.8×107CFU/g, 5.1×107CFU/g and 4.2×107CFU/g, respectively, which prepared microorganisms agent. According to the water solubility of the organic, mixed the organic with some hot water, and exposured with air violently in high-speed by a electric stirrer, then prepared the simulated synthetic sewage containing TEXTB.The study was carried out in a 1L conical flask made of glass, with working volume of 0.65L. The reactor's temperature was kept at 25°C±3°C by the automatically boiling water bath pot, and operated in ventilation hood in room temperature. The reactor was operated in sequencing batch mode, with a cycle of 24 h. The cycle consisted of five phases: filling, aerobic reaction phase (23h), settling phase (0.5h), decanting phase and idle phase (0.5h). filled and decanted manually, and five-stage influent concentration gradient increased program was adopted.In the study the effect of bioaugmented system(BS), which added activated sludge with microorganisms agent was compared with non-augmented system(NBS), which was not added microorganisms agent and only started with conventional activated sludge. Its impact on the removal efficiency of COD and the capability of system enduring shock loading after augmented with agengt were studied. Supply amount were also investigated. Results showed that, the start-up time for the SBR was shortened by augmentation with high effect bacteria, its ability to endure shock loading was strengthened, and removal efficiency of COD was improved.Bioaugmented system can maintain consistent removal after 10 hours of augmentation with 10% supply amount(effluent COD<100 mg/L), while the control system without the addition of agent needs 36h to reach the demand fundamentally. The average value of the initial influent COD is 643mg/L, the average value of the effluent COD is around 160mg/L, the removal efficiency can go up to 94% due to relatively low influent. When the influent COD maximum reaches to 1221mg/L, COD removal efficiency falles below 50%, 35% on average. With the concentration of COD, their removal reduced gradually. When the volumetric loading rate rises from 0.692Kg/m3·d to 0.751Kg/m3·d, COD removal efficiency falles simply to 27.4%. Change of the concentration of influen COD affectes the effluent COD greatly. Removal efficiency of BS maintained at above 90% from beginning to end, can reach maximum 96%, and endure maximum volumetric loading rate of 1.020Kg/m3·d. And can maintain stabilized higher removal efficiency, which improved significantly compared to NBS system.The ultraviolet-visible light spectrum chromatographic analysis of effluent quality also reflects the strengthening effect of bioaugmentation. Blank sample existes five peaks obviously in the curve line, which illustrates five types of substances existing in sample. System augmented with agent showes no clear peaks in the curve line proves that no more organic pollutant existing in sample. Pollutant has been effectively dealt with after augmentation with agent, and the numerical value of effluent further illustrates this problem. Scanning curve of non-augmented system without the addition of agent existes peaks obviously proves that there still existes organic pollutant in sample. The higher the value of effluent COD, the higher the peak curve of scanning curve.The study summarized the possibility of the application of bioaugmentation in dealing with refractory organic.The results presented in this study demonstrated successful application of a bioaugmentation strategy to improve the performance of aerobic reactor operated in sequencing batch mode operation treating wastewater containing refractory organic in the lab. The study discussed the treatment of sewage containing aromatic mixture in laboratory-scale, which provides some certain light for refinery refractory organic wastewater operating.