Study On Nearshore Ecological Remediation Of Nitrogen And Phosphorous Pollution And Bioenergy Extraction From Macroalgae

Large quantities of nitrogen (N) and phosphorous (P) nutrients are transported into the coastal ocean, which introduce the eutrophication of sea water, contributing to a series of ecological problems, like harmful algae bloom (known as HAB). Thus, it's an important subject to control the N and P pollution in coastal ocean.By in-field investigations and the use of 226Ra tracing technique, it is confirmed that submarine groundwater discharge has an ineglectable effect on near shore eutrophication, and it's one of the reasons for the on-going N and P pollution in coastal oceans.The in-situ remediation of N and P in sea water can help reduce the pollution. Through modeling experiments and in-situ investigation, the thesis studied the N and P absorption characteristics, process and its influencing factors of the macroalge—Laminaria japonica (also called as kelp in China). It is found that nitrate, ammonia and phosphate in the culture media are absorbed efficiently by the kelp, which can be a remediation alga for N and P pollution. And the suitable conditions for N and P absorption are confirmed. These results make large scale kelp cultivation an effective way to control the near shore eutrophication.In order to utilize the harvest kelp, the extraction of bio-energy is also studied. The carbohydrate in the kelp is the main source for bio-energy extraction. After various pretreatments and optimization of the cultivation conditions, the enzymatic treatment, using protease, cellulose and pectinase, shows the best result, obtaining an ethanol yield of 3.32g/100g DW, fermented by Saccharomyces cerevisiae. The economic feasibility and ways to improve the kelp value are also investigated, offering a basis for integrated utilization of the kelp.