Study On Remediating Eutrophic Water With Immobilized Nitrobacteria-modular Submerged Plant

Water is the source of life and the basis of the survival.However the world has more than one-third of the lakes(reservoirs)showing varying degrees of eutrophication.The eutrophication of water is one thing we have to take seriously.So far,many studies have proved that microbes or submerged plants can effectively recover eutrophic water.In addition,the combination of microbes and aquatic plants has also begun,but most of the methods are to put microorganisms and plants into the eutrophic water to be treated to purify the water.In this paper,we used direct extraction of highly heterotrophic nitrifying bacteria from Taihu Lake sludge.And the heterotrophic nitrifying bacteria were optimized and fixed and then combined with the modular submerged macrophylla and Euphorbia lobate to recover eutrophic water.the fixed bacteria solve the problem that bacteria easily flow with water.The modular aquatic plants solve the problem of planting and harvesting for water plants or other issues when recover the eutrophic water.In addition the modular water plants use the combination of Pleurotus ferulae increasing the diversity of species in the water system.It not only purifies the eutrophic water but also increases the stability of the water ecosystem.At the same time,It prevents the recurrence of water deterioration and provides theoretical basis for the exploration of eutrophication of Taihu Lake.This study mainly includes three pieces.1.Heterotrophic and efficient nitrifying bacteria screening and identification.2.Determination and optimization of embedding conditions of heterotrophic nitrifying bacteria.3.Immobilized nitrifying bacteria combined with modular submerged plants on water quality.(1)Through the enrichment of nitrifying bacteria and multiple purification screening from the Taihu Lake sludge,we selected five strains of bacteria which grow well.After the observation of bacterial morphology and comparison of "Berger's bacteria identification manual",we initially identified the five strains of bacteria as heterotrophic nitrifying bacteria.And then,the nitrifying bacteria were tested for nitrification and ammonization respectively.The results showed that all five nitrifying bacteria had strong ability to degrade ammonia nitrogen and nitrite nitrogen.What'smore,bacteria J-4 has the best transformation effect.The transformation rate of nitrite nitrogen and ammonia nitrogen reached 69.00% and 90.25% respectively after been cultivated for 48 h.Through 16 SrDNA identification,bacteria J-4 belongs to the Dyadobacter fermentans.Then we build the phylogenetic tree of strains bacteria J-4.(2)According to the materials used in previous studies,we selected sodium alginate(SA)polyethylene glycol(PEG)immobilized embedding carrier material through a series of comparative tests.The orthogonal test concentration of sodium alginate(SA),polyethylene glycol(PEG),activated carbon(AC)and CaCl2 were1.5%-2.5%,7%-9%,1.5%-2.5% and 2%-4% respectively by single factor test.The orthogonal experiment and variance analysis results show that:In the four kinds of materials,sodium alginate(SA)has the largest effect,followed by polyethylene glycol(PEG),CaCl2,and activated carbon(AC).The optimal concentration of Carrier for embedding material sodium alginate(SA),polyethylene glycol(PEG),activated carbon(AC)and CaCl2 were 2.5%,8%,1.5%,4%.(3)For other conditions in the same situation,we design six processing: A,controls water;B,control water + free of bacteria C,controlled water + immobilized bacteria D,controlled water + modular aquatic plants,E,controlled water + free bacteria + modular aquatic plants,F,control + water + immobilized bacteria modular aquatic plants.The nitrogen and phosphorus removal effect of group F is best,overall were superior to that of immobilized bacteria,modular vallisneria natans and Elodea nuttallii alone and when to replace free bacteria immobilized bacteria effect.Combine the two,in 12 days,the removal rate of TN,NH4-N,TP,and the CODMn was 84.22%,99%,73.79% and 41.24% respectively;The regression equations showed that: the removal ability of TN,TP and CODMn from large to small in turn was F>E>D>C>B.