The Influence Of Environment Factors On Microcystis Producing DBPFP And Its Mechanism

In recent years, the situation of eutrophication in our country is quite grim, over 80% of lakes and reservoirs is involved.Many reservoirs and lakes where the drinking water come from have great algae blooms caused by eutrophication. When this kind of water containing algae is treated by chlorination, the algal cells will die and rupture, releasing disinfection by-product precursors. And the precursor will react with chlorine, producing various disinfection by-products which can cause cancer. Unlike natural organic matter, algae are living creature which has certain sensitivity to the change of environmental factors. So environmental factors change is bound to influence its ability to produce disinfection by-products precursor material.In order to figure out this problem, this topic select the microcystis as the research object, which is the dominate algae when algal blooms outbreak, to find out the formation dynamic laws of three typical DBPs(CHCl3, DCAA and TCAA) when algae metabolites react with plenty of chlorine disinfection. The results show that the three kinds of DBPs will stay stable after the reaction start 3 days, and the yield of those DBPs is CHCl3 > DCAA > TCAA. The three kinds of disinfection by-products formation reaction conform to first-order reaction kinetics model, the fitting results of the Origin software show that the R2 > 0.90, so the fitting effect is quite good. According to the reaction rate constant k, we can conclude the reaction priority of DBPs that TCAA > CHCl3 > DCAA. Besides, the typical metabolites protein and polysaccharide reacted with plenty chlorine is observed, finding that the reaction also conform to first-order reaction kinetics model and protein have a priority when the reaction is start, compared to polysaccharide.To reveal the influence on microcystis algae produce disinfection by-products precursor capacity by environmental factors, this research culture microcystis on the control of a single factor: the growing period, temperature, p H, light intensity, and the concentration of nitrogen, phosphorus, to investigate the DBPFPs of those microcystis under the different condition after 7 days. The results show that:(1) The DBPFPs of microcystis in decline phase are mainly concentrated out of cell; the DBPFPs of microcysits in stable phase are mainly concentrated in cell; the density of the logarithmic microcystis is lower, while its DBPFPs is relatively low.(2) The microcystis on 25℃ condition have the most capacity to produce DBPFPs.(3) The microcystis on p H=7 condition would produce more DBPFPs than those cultured in weak base and weak acid environment.(4) When the light intensity is more than 3300 lx, the microcystis produce less DBPFPs with the increases of light intensity.(5) Nitrogen concentration has little effects on the yield of DBPFPs, while phosphate concentration, no matter too high or too low, will inhibit the microcysitis producing DBPFPs.