Preliminary Studies On Pollution In Yundang Lagoon, Xiamen Bay And Its Microorganism Bioremediation

With the acceleration of urbanization and the improvement of industrialization process,the level of pollution in urban lakes is more and more serious and the waters are in eutrophic state.The eutrophication of water environment seriously restricts the city's economic sustainable development and has effect on the resident life quality. Bioremediation is a new technology which has many advantages such as low investment,high efficiency and no secondary pollution.Now the technology has been successfully applied to the fields of wastewater treatment,agriculture,animal husbandry,aquaculture and environmental protection.This study is focused on the pollutant level of sediments after 20 years continuous rehabilitation in Yundang Lagoon and bioremediation of the polluted water by direct adding different kind of mixed microorganisms.Main work and results are as follows:(1) Different techniques such as Inductively Coupled Plasma Mass Spectrometry, Gas Chromatography and elemental analysis were employed to characterize the heavy metals,nitrogen,sulfur and organic matter in the sediment of Yundang Lagoon. Polymerase Chain Reaction--Denaturing Gradient Gel Electrophoresis(PCR- DGGE) analysis of 16S rDNA genes was carried out in order to determine the microbial diversity of Yundang Lagoon.The results show that the pollution in Yundang Lagoon was moderate and the ranking of heavy metals followed the order:As＞Ni＞Pb＞Cu＞Cr＞Zn.The contents of TN,TC,TOC and TS from surface sediments of Yundang Lagoon were the highest and the distribution of the stations were as follows:S2＞S3＞S1＞S4.The total content of sixteen PAHs from four stations of Yundang Lagoon followed the order:S2＞S3＞SI＞S4,and mainly came from incomplete combustion of fuels such as gasoline,diesel and coal.n-Alkanes were mainly distributed in the nC₂₂-nC₃₀ and mainly from aquatic plants and land-based plants.Fatty acid from four stations contained the following:C10:0,C12:0,C14:0,C15:0,C16:0 and C18:0, indicating the contribution of microalgae to the sediments.Total DNA was extracted from sediments with the Phenol-Chloroform Extraction method,and the V3 variable region of 16S rDNA gene was PCR-amplified.DNA fragments of 200 bp were obtained as PCR products.DGGE analysis of 16S rDNA genes showed that the community diversity was abundant in different stations of Yundang Lagoon.(2) Bioremediation of real wastewater from Yundang Lagoon was carried out by direct adding different kind of effective microorganisms(EM) in order to change water quality effectively and provide the basic data for rehabilitation.The results show that maintaining dissolved oxgen at 5-6 mg/L by gentle aeration was effective to bioremediation process.EM were more capable of degrading organic matter than CB and had combined effect on bioremediation of polluted water.The enrichment of EM showed that four predominant microorganisms(photosynthetic bacteria,yeast, lactobacillus and actinomycete) could be cultivated by different methods.Change of the dosage of microorganisms in EM would influence the effect of bioremediation. The optimal adding dosage was 0.8 mL enriched bacteria(four predominant microorganisms in accordance with the proportion of 1:1:1:1).The removal rates of COD_Mn,TN and TP were 39.56%,66.98%and 68.42%during the experiment, respectively.The concentration of pollutants in water also influenced the effect of bioremediation.COD degradation rate was increased and the removal time of COD was shorter during the treatment of higher polluted water bodies by EM.