The Preparation Of Controlled-released Fertilizer And Their Application On Spilled-Oil Bioremediation Of Intertidal Zone

Boremediation, which has many advantages such as less secondary pollution and low-cost, has become the important method to remove petroleum hydrocarbon pollution in oil-spilled shoreline. In the oil-spilled shoreline, nutrients such as nitrogen, phosphorus usually are the main limiting factors to biodegradation. In order to thoroughly degraded petroleum and purified the environment, we often strengthen the biodegradation of pollutants by adding nutrients.This research chose Tianjin shoreline, which was the area of high incidence of oil spilling, as experimental site to comprehensive study of field investigation, laboratory handling and on-site simulated bioremediation. Based on the field investigation of the typical characteristics of the ecological environment of Bohai Sea coastline, we developed fertilizer which is both lipophilic and slow-released according to the characteristics of petroleum hydrocarbon degrading bacteria on nutrient absorption and utilization of different sustained-release fertilizer. Based on the evaluation of lipophilic efficiency, slow-released efficiency and the impact to bioremediation in laboratory, through the further in-suit test to study the role in the process and mechanism of the slow-released fertilizer in bioremediation of oil-spilled shoreline, in order to seek a theoretical foundation and scientific basis of the development of slow-released fertilizer and its application in the bioremediation of oil-spilled shoreline. The main results of this research are shown as follows:(1) The investigation result of ecological environment of 23 stations Round Bohai Area in Summer,2008 shows that the environmental factors such as temperature, pH, DO et al Round Bohai Sea are appropriate for the growth of hydrocarbon degrading bacteria. The organic pollution of Round Bohai Sea Area are serious, petroleum hydrocarbons and TOC are between 57.90 mg/Kg-2788.60 mg/Kg and 0.15%-6.16% respectively, there are 70% and 61% of total stations higher the National Sediment Quality Criteria class 1. High value areas are mainly located in Pier 6 of Tianjin Port, Tianjin Hangu Caijiabao Pier, Caofeidian and Liaoning Yingkou Liaohe River Estuary. The eutrophication of Round Bohai Sea Area is also serious, the total dissolved nitrogen (TDN) and total dissolved phosphorus (TDP) in matrix pore water are between 15.75μmol/L-55.70μmol/Land 1.10μmol/L-2.17μmol/L respectively. However, the lack of nitrogen and phosphorus are still the main limiting factors to bioremediation. The number of heterotrophic bacteria, petroleum hydrocarbon degrading bacteria, alkane degrading bacteria and aromatic degrading bacteria are between 4×104-7.40×106CFU/g,0-8×105CFU/g,170-3.50×106CFU/g and 0-1.58×103CFU/g respectively. The alkane degrading bacteria are more abundant, while the number of aromatic degrading bacteria is small.(2) Through laboratory single factor experiments, we found the optimum conditions and technology of preparing lipophilic and slow-release fertilizer, which make particulate nitrogen and phosphorus as the core layer, sulfur as the coating layer, polymer wax as the outer layer. The fertilizer has the highest slow-released efficiency when the sulfur core layer is 20%, the polymer wax layer is 4%, the surface conditioner is 1%, spraying temperature is 170℃. The fertilizer has good sustained release efficiency not only in different salinity and pH of the seawater, but also can maintain the growth of hydrocarbon degrading bacteria with sustained released nutrients, and promote hydrocarbon degrading bacteria degrading the crude oil components, including alkanes and aromatic hydrocarbons, the degradation rate of n-alkanes increased by 13.9%-59.0%, with an average of 41.2%; the degradation rate of aromatic compounds increased by 9.6%-32.3%, with an average of 19.9%.(3) Apply the lipophilic slow-released fertilizer in the in-suit oil-spilled bioremediation field of medium crude oil and heavy crude oil, and compare the efficiency with water-soluble fertilizer. The result shows that both slow-released fertilizer and water-soluble fertilizer can greatly improve the level of the nutrients in Matrix pore water. But water-soluble fertilizer are easily washed away because of water erosion and make it has a extremely weak Fertilizer effect (≤7 days), however the slow-released fertilizers has a release cycle of up to 25-30 days. In the release cycle, the fertilizer can release enough nutrients stably to maintain the growth of microbes, The number of heterotrophic bacteria, petroleum hydrocarbon degrading bacteria, alkane degrading bacteria and aromatic degrading bacteria in the system adding slow-release fertilizer are much high than that in the system adding water-soluble, the PCR-DGGE result shows that the microbial community heterotrophic bacteria, petroleum hydrocarbon degrading bacteria, alkane degrading bacteria and aromatic degrading bacteria in the system adding slow-release fertilizer are much high than that in the system adding water-soluble, the PCR-DGGE result shows that the microbial community structure of the system adding slow-released fertilizer and microorganism preparations are significantly different from that adding water-soluble and microorganism preparations and Oil control system, which means that the slow-released fertilizer can not only promote the growth of the indigenous microorganisms but also the growth of exogenous microorganisms. For both medium crude oil and heavy crude oil, the most effective way to Improve the efficiency of bioremediation is adding slow-released fertilizer and microorganism preparations, it can not only improve the biodegradation rate of the alkanes but also aromatic hydrocarbons components. For medium crude oil, the degradation rate in the system adding slow-released fertilizer and microorganism preparations are 1.4 times higher than that in oil controlled system; for heavy crude oil, the degradation rate in the system adding slow-released fertilizer and microorganism preparations are 1.5-2.7 times higher than that in oil controlled system. This paper can provide a theoretical foundation and scientific basis both for the development of slow-released fertilizer and its application in the oil-spilled shoreline; it also can improve the bioremediation technology for oil-spilled shoreline and support the wide range usage of bioremediation.