Experimental Research About Hydrogenotrophic Denitrification For The Removal Of Nitrate In Groundwater

With the progress of society and the rapid development of industry and agriculture,human dependence on groundwater is increasing. Because of the surface ecologicalenvironment pollution and destruction, the groundwater quality gradually deteriorated.Groundwater pollution problems become more serious, the protection of groundwaterresources has become one of the world’s major environmental issues. Nitrate and nitritehas gradually become the popular factors of the groundwater pollution. Nitrate andnitrite could cause a series of problem such as high iron protein disorder, cancer, so thisproblem received extensive attention of researchers all over the world.So far, no more mature technology can be specifically used for the removal ofnitrate in groundwater. Today, the major task of water treatment is developed a stable,economic and environmental protection technology for removal nitrate in groundwater.Under hypoxic conditions, the hydrogen autotrophic denitrifying bacteria can usehydrogen as an electron donor reduction of nitrate in groundwater. The technology ofhydrogen autotrophic denitrification removal nitrate in groundwater with advantages ofclean and efficient, no secondary pollution, economic and environmental. In this thesis,established a quantitative method analysis of the hydrogen autotrophic denitrifyingbacteria biomass, studied the characteristics of hydrogen autotrophic denitrificationbacteria in different conditions. The main results are as follows:⑴By enrichment culture and purification, succeeded in screening high efficienthydrogen autotrophic denitrifying bacteria H2-117, H2-118, H2-128and iron autotrophicdenitrifying bacteria Fe–118.⑵The optimum pH of the hydrogen autotrophic denitrification bacteria and ironautotrophic denitrification bacteria is7~8. This range is most suitable for removal nitrate of autotrophic denitrification biological.In additional, cell growth and theremoval efficiency of nitrate is high in this range also. The nitrate removal efficiency ofthe three hydrogen autotrophic denitrifying bacteria are94.30%,95.38%,94.23%, ironautotrophic denitrification bacteria of nitrate removal rate is87.13%. The optimumtemperature range of the screening autotrophic denitrifying bacteria is30℃~35℃.When the temperature is30℃, denitrification rate of two kinds of autotrophicdenitrifying bacterias all are high, generally the residues nitrite below0.3mg/L.⑶The C/N has little effect on the desulfurization process of the hydrogenautotrophic denitrification bacteria and iron autotrophic denitrification bacteria. Theoptimum C/N of the bacteria is3~4.5. Considering the economy, to control the C/Nabout3is the best choice.⑷Autotrophic denitrifying bacteria involved in denitrification process, and directlyaffected the denitrification process. The nitrate concentrations sharply decreased as theproliferation of denitrifying bacteria increased, the removal efficiencies of nitrate are allup to about90%. Autotrophic denitrifying bacteria have less residual nitrite, usuallyabout1mg/L.