| The in situ repair of sediments is an effective means that can fundamentally solve the continued pollution of the urban river.Microorganism community occupies an important position in the migration of nitrogen and phosphorus elements. By the denitrification of microbes, nitrogen element can be removed from the system permanently. Meanwhile the fixation effect of bacteria will reduce the release of phosphorus, so it can reduce the risk of eutrophication. The foundation of Anti-pollution is the key of in situ bioremediation of sediment. In this paper, Guangzhou heavy pollution river was studied as an example. In aim to solve the problems of low dissolved oxygen and excess nitrogen and phosphorus pollutants, and base on the view of building a micro ecosystem that have high efficiency degradation of pollutants, the influence of changing of overlying water dissolved oxygen and pH on the microbial community were researched. And then the investigation methods of micro ecology system structure and bacteria activity were sifted. At last, the effects of bioaugumentation to the biology community structure in the sediment by addition of bio-energizer were researched. The results showed that:Dissolved oxygen and pH were the important factors that influenced microbial growt h. In the high dissolved oxygen conditions, sediment pH and ORP were increases, and t he microbial community changed from anaerobic type to aerobic type, nitrobacterium and heterotrophic bacteria had large growth, the phosphate-solubilizing bacteria was decline, so it could promote the change fromeNH3-N to NO3-N, and weaken the microbial activat e effect to the phosphate content, the soluble nitrogen and phosphorus transformed into c ombination state of iron and manganese, reduced mobility of nitrogen and phosphorus. U nder the Anaerobic conditions, the microorganism communities evolved to the anaerobic t ype, nitrobacterium and nitrosobacteria number decreased greatly, so the nitrogen cycle w as obstructed, and sediment ORP had reduced, that caused a large release of nitrogen an d phosphorus. pH had an big effect on the microbe in sediments. Ammonifier and inorg anic phosphorus bacteria were decreased in acid conditions so the mineralization rate of organic matter was reduced. Amount of nitrobacterium was improved in alkaline conditio ns, and improved the transformation of ammonia nitrogen, but alkaline conditions blocked the growth of heterotrophic bacteria. So acid and alkaline environment both had adverse effects on the sediment microbial diversity, enzyme activity declined, neutral condition was more advantageous to the sediment microbial growth.Contrasting the oxygen uptake rate(OUR),dehydrogenase activity and the change la w of sediment FDA activity under the same experimental conditions, it could be seen th at three characterization method could get the same change trend of microorganism activi ty. The oxygen uptake rate of sediment could be reflected in the proportion of nitrobacte rium,nitrosobacteria and heterotrophic bacteria, but testing of OUR was existing errors by the affect of atmospheric oxygen enrichment. Dehydrogenase activity represented the e lectron transfer rate in the sediments. Activity of sediment in the reducing condition was more accurate. Though FDA activity was affected by the sediment microbial biomass, it was a more comprehensive reflection of the microbial activity, so this paper chooses th e FDA as active investigation means.Five diversity indices for sediment microbial community under different aeration con dition were contrasted based on BIOLOG ECO microplates. The results show that the A verage Well Color Development (AWCD) of saturated dissolved oxygen condition is high er than the experimental group without aeration. Shannon index and evenness, Simpson i ndex, McIntosh index and evenness are decreasing at first and then increase. After60da ys experiment, the sediment microbial community has evolved, community diversity of ae robic condition is higher than other conditions. ECO method could get fully structure fea ture of the microbial community, and reflected the using of a single carbon and different carbon sources of the microorganism, so could concluded the sediment microbial diversit y with different physiological and biochemical indexes. In this article, ECO microplate w as chosen to reflect the effect of foundation of micro ecosystem.CaO2, Nitrate of lime and hydrogen peroxide could improve the DO content and ORP of sediment, improve the reducing environment, but they were based on different oxidation principle. The CaO2could react with water and produced oxygen, so it could improved the DO of overlying water, promoted evolution of the microbial community; Ca(NO3)2acted as electronic receptors for denitrification in the sediment, it could stimulate denitrifying bacteria, and promote the degradation of the organic matter, slow down the consumption of DO; Hydrogen peroxide could decompose organic matter for its strong oxidation, but had poisonous effect on the sediment microbes, and it could inhibit microbial growth. So contrasted with the characteristics of three sediment repair method, CaO2could be used as a aerobic technology, on one hand, it could improve the DO of overlying water, on the other hand, nitrogen and phosphorus could combined with calcium that could deposit into the sediment, so it could inhibit the release of nitrogen and phosphorus; Ca(NO3)2could be used as microbial activation agent, which could promote the sediment heterotrophic bacteria growth and the decomposition and mineralization of organic matter.Amino acids and small molecular organic acid were helpful for the improving of sediment microorganism activity, and promoted the degradation of total organic matter in the sediments. Through the experiment, the formula of composite biostimulant was determined:1. Amino acids, including Lysine, Isoleucine, Tryptophan, Glycine and Glutamic acid;2. Carbon source, including Glucose, Sodium lactate, Sodium citrate, Xylose and D-galactose;3. Large elements, including NaH2PO4, MgSO4, KCl, NaCl, MgCl2, FeCl3;4. Trace elements, including EDTA, FeSO4,(NH4) Mo7O4, CuSO4, CoCl2, CaCl2, ZnSO4, MnCl2;5. Sediment oxidant, including CaO2and Ca(NO3)2.Through the indoor static test, an investigation on the micro-ecology system construction and in situ stabilization effect of sediment had been discussed. Conclusions showed that, through the adding of composite biostimulant, the sediment microbial system activity increased; Compared with the blank group, by adding of30ppm composite biostimulant, the microbial community evolution cycle shorten from15days to6days; by adding60ppm,120ppm and250ppm, the microbial community diversity was higher than that experiments without adding the biostimulant. Meanwhile the utilization of carbon source and species were increased. The degradation rates of TOC were separately5%,7%,10%and15%. Micro-ecology system that was able to bear or endure pollution had been set up preliminarily, and had positive effect on the in situ repair of sediment. |
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