Research On Restore The Polluted Groundwater By The Synergistic Effect Of Autotrophic And Heterotrophic

At present,The nitrate pollution from groundwater has seriously affected People’s lives in many countries and regions, As we all know, China is a large industrial and agricultural country,And being in the stage of rapid development of developing countries. That makes our nitrate pollution more serious.The water polluted by nitrate will not only do harm to our health, cause cancer, but also restricts the development of industry and agriculture of our country. The biological denitrification method is more economical and practical than the physical and chemical method, however, the shortage of the organic carbon source has been limited to the nitrogen removal of heterotrophic denitrification in our country. This study solved this problem from the following two aspects: First, a new type of carbon material with slow release function was created by straw, polyvinyl alcohol(PVA), cellulase and other raw materials, and the compressive strength, structural properties and carbon release properties were studied;second, Establish the electrode biofilm reactor and add the carbon release material to the reactor. Making the polluted groundwater be restored by the synergistic effect of autotrophic and heterotrophic.In this study, polyvinyl alcohol(PVA), straw, five kinds of amylase are used as raw material, According to orthogonal test, the raw materials are divided into 5 groups according to different proportions, 5 groups of 28 kinds of carbon materials release are prepared by the gel forming process after pretreatment, solution blending,injection molding mould, frozen four stages. Make the mechanical testing of materials by the microcomputer control electronic universal testing machine. The results showed that the straw and PVA could be well mixed, and the compressive strength was about 1066.67KN/m2, which could meet the pressure of the material in the underground water, and the higher the PVA content, the stronger the compressive strength;Analyse the material surface structure by scanning electron microscopy(SEM), Results show that PVA as matrix material to wrap straw into a fixed shape, The two kinds of material has good biocompatibility and with the two-phase content changing, the surface morphology also showed a gradual changing trend; The higher the straw content, the higher the carbon content released from material, and when the material additive for cellulase, the material release carbon performance is best. Through the orthogonal test table of the ratio of the material, The order of effective extent that dffect the carbon releasewas Straw,PVA, additive, add dose; Through fitting the static release data of the materials at room temperature, the formula for the kinetic formula of the carbon release is finally obtained,The higher the K value, the better the release of carbon.The autotrophic reaction stage results of this study showed that: NO3--N removal rate with the current intensity is increased first and then decreased with the current intensity increasing. When the current is 150 m A, NO3--N removal rate reached the maximum, the removal rate was 27.5%, it is the best removal effect; Different influent concentrations can effect the denitrification. During the test, with NO3--N concentration increased, NO3-- removal rate decreased, and NO2--N concentration a. increased. When the influent concentration is more than 30mg/L, the nitrogen removal rate decreases rapidly; Hydraulic retention time has obvious effect on denitrification. In a certain range, the longer HRT,the higher NO3-- N removal rate, at rhe sanme time the NO2-- N accumulation was reduced. But from the economic considerations, 12 h was identified as the best HRT autotrophic stage.Autotrophic heterotrophic synergistic reaction stage results are as follows: hydraulic retention time is too long or too short will limit reactor NO3--N removal efficiency, and the long hydraulic residence time will cause accumulation of NO2 –N. When HRT was 8h, the removal rate of NO3--N was the highest, up to 98.8%; Due to lack of hydrogen or hydrogen inhibition phenomenon, The current is too large or too small will decrease the NO3--N removal efficiency and cause the accumulation of NO2--N.The current intensity of 50 m A is the most ideal, and the NO3--N removal rate is 90%, and there is no obvious accumulation of NO2--N in the treatment of simulated groundwater; Temperature influenced enitrification by effect denitrification bacteria in reactor,The high or low temperature will affect the enzyme activity of bacteria,thereby affecting the removal rate of NO3--N and the accumulation of NO2--N. Considering the economic costs and the quality of effluent water, this experiment will set the temperature of 30℃, at this time the removal rate was 84.3%; with influent concentration increased NO3--N removal rate decreases slowly and gradually produce nitrite accumulation phenomenon test initial NO3--N concentration is 30mg/L.High throughput sequencing was performed on two samples taken from the composite system. The results showed that the Coverage index of the two samples were all above 0.999, and the results were true. Shannon and Simpson index value show that autotrophic heterotrophic denitrifying bacteria has more abundant bacteria diversity compared with pure heterotrophic denitrifying. 12 bacterial phyla wewe found in autotrophic heterotrophic contact surface of carbon materials sample. Among them, Proteobacteria has the largest proportion, the abundance of the sample was 98%, and the second dominant bacteria phyla in the sample was the Bacteroidetes, which was 1.06% in the sample. Pseudomonadaceae and s Sphingomonadaceae were the dominant bacteria, The proportion was 48.08% and 22.7% respectively. Pseudomonas have the maximum abundance in the genus which is 37.4%. Pseudomonas is a relatively common type of anti nitrification bacteria.Second bacterial genus in the sample is Sphingobium,which proportion is15.07%.