Effect Of Nutrients On Biodegradation Of Oil Pollutants In Seawater And Optimization

With our country economy's development, the demand of petroleum products increased substantially, but because our country petroleum mining quantity is limited, oil transport and various types of ships are flourishing more and more daily. In our country, petroleum is the most main pollutant in the offshore seawater and pollution scope is broader. After sea water suffers oil pollution, its petroleum degradation rate is influenced, in addition to by microbial degradation, chemical and physical characteristics of pollutants factors, also by supply of nutrients. The petroleum pollutant provides mainly carbon, hydrogen, lack of oxygen, nitrogen; phosphorus in the water is most likely to constraint microbial degradation of oil. Therefore, studying on the effects of nutrition to microbial degradation in the seawater has extremely important significance.This research studys that effection of nutrients on biodegradation of oil pollutants in seawater. The results of the investigation are as follows:1. Exerting N and P nutrition salt may promote petroleum pollutant biodegradation, may reduce resident time of pollutant in the environment and may cause oil pollutant half-life to reduce from 25d to 5d. Exerting nutrient salt have the obvious promoter action to indigenous fungus in the degeneration oil aspect, the biggest degeneration rate enhances from 28.91% to 53.64%. By exerting N, P nutrients and simultaneously exertsing Mg²⁺, Fe³⁺, and other trace elements, biodegradable rate of oil pollutants can reach 83.7%.2. The degradation of the diesel makes best effect to more than 60 percent at pH 7.0～7.5, and the cell has a higher degree of concentration (0.387～0.409, for the minimum of 2 times). The diesel oil degeneration rate increases along with the oxygen dissolution quantity increasing rapidly When oxygen dissolution quantity is 5.25～6.86mg/L. the degeneration rate achieves 61.37% When the oxygen dissolution quantity is 6.86mg/L. Therefore, rotate speed is 120r/min.3. Compared with the ammonium salt, the nitrate nitrogen is remarkable effect in the stimulation microorganism growth aspect, but the microorganism first absorbs is ammonia nitrogen and the ammonia nitrogen existence can limit microorganism absorption the nitric acid nitrogen. Compared with the organic nitrogenous, the microorganism is favor to using inorganic nitrogen as N source. Best C:N:P approximately is 150:10:1.4. Exerting the simple inorganic nutrition and the slow release urea, the former is quite obvious to the diesel oil degeneration rate. Throws interruptly compared to throws directly enhance diesel oil degeneration rate.5. Six conditions which affect the diesel oil degeneration rate are carried on screening optimization by using Plackett-Burman (PB) and central composite design (Central Composite Design). The PB experimental design and statistics analysis indicate: The nitrogen source, the phosphorus source and pH are three key aspects affecting the diesel oil degeneration rate. Take the diesel oil degeneration rate as the response goal and carry on the central composite design to three factors, we can obtain the influence diesel oil degeneration rate second-order model after the response surface law optimization analysis,make sure most superior operating condition: Nitrogen source (NaNO₃) 0.143, phosphorus source (KH₂PO₄) 0.022, pH 7.4.