Research On Biodegradation And Kinetics Of Bilge Water

With the development of the shipping industry,people are paying more and more attention to the problem of the damage to the marine environment caused by the oily bilge water.This kind of oil sewage contains a lot of emulsified oil and petroleum hydrocarbon pollutants.If it is not treated well and discharged at will.When the sewage enters into the water or soil,it will bring a huge potential threat to the ecological environment and human health.At present,the common methods of treating the oily bilge water of ships mainly include physical method,chemical method and biological method.Although biological method has the characteristics of safety,reliability,low cost,good treatment effect and no secondary pollution,it is mainly used in the research of soil pollution treatment,and the research of using biological method to treat the oily bilge water is rare.In this paper,the degradation bacteria were isolated and screened from the oily bilge water environment.According to their properties,they were classified and studied in the biological pool device.The degradation conditions were optimized,the degradation characteristics were studied and the removal effect of petroleum hydrocarbon pollutants was evaluated at the same time in order to verify the biodegradation ability of the biological pool device.Then the theoretical basis and technical support were provided for the biological method to remove the oily bilge water from ships.The main research contents are as follows:?1?Five aerobic bacteria and one anaerobic bacteria,named S1?S5 and SG-1respectively,were domesticated and isolated from the oily bilge water of a supply ship.The results showed that the degradation rates of S1,S2,S5 and SG-1 were higher.The molecular identification results of 16S r DNA of the four dominant strains were as follows:S1 was Bacillus toyonensis,S2 was Bacillus licheniformis,S5 was Bacillus albus and SG-1 was Rhodopseudomonas palustris.The bacterial consortium of aerobic bacteria were constructed,and the degradation rate of S15 to diesel oil in 7 days was83.12%,which was the object of follow-up study??2?Taking the anaerobic SG-1 as the research object,the significant factors influencing the degradation rate of the strain were screened through single factor experiment,and then the best degradation conditions were obtained through response surface?RSM?optimization:the temperature was 29.85?,the p H was 6.94 and the inoculation amount was 6.08%,the maximum degradation rate was 89.0456%,and the actual experimental value was 88.95%.The prediction data of response surface was reliable.?3?Taking S15 as the research object,under different environmental factors,the optimal growth temperature of S15 is 35?,the salinity is within 2 g·L^-1,and the optimal p H value is 7.5.Under the action of surfactant,the bacterial consortium showed very high emulsifying ability?more than 80%?and CSH value?more than 50%?.Biosurfactant played the role of emulsifying solubilizer in the degradation process of petroleum hydrocarbon pollution,and promoted the uptake and degradation of diesel oil by bacterial consortium.The results of GC-FID showed that S15 had the best degradation effect on the short chain alkane C₁₀?C₁₃,the average degradation rate was97.84%,and for medium chain and long chain alkane,the average degradation rate was80.73%and 81.57%respectively,in 7 days.?4?The degradation kinetic equation of SG-1 was lnc=-0.0215t+3.7587.The effective degradation rate of the carcinogen phenanthrene?PHE?in the biological pool system within 24 h reached 75%.The average value of diesel oil pollutants in the bilge water treated by the biological pool device is 13.92 mg·L^-1,which meets the requirements of Discharge standard for water pollutants from ships;the average content of COD is 29.5 mg·L^-1,and the average removal rate is 89.1%,which meets the national level I discharge standard.