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Abstract:
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Autotrophic denitrification is an effective treatment technique for nitrate removal from groundwater . Six basic elements are required for the growth of autotrophic denitrifiers : (1 ) electron donor , (2 ) electron acceptor , (3 ) active bacteria , (4 ) anoxic /anaerobic environment , (5 ) micronutrients , and (6 ) optimum pH and temperature . In this research , granular sulfur is an electron donor ; nitrate is an electron acceptor ; anoxic and anaerobic environment was maintained in the reactor , and micronutrients were added ; pH was controlled between 6 and 9 , and temperature was maintained at the room temperature (20 + 2 oC ) . Batch reactor and continuous up -flow reactor experiments were carried out to investigate the denitrification rate , and reaction rate kinetic constants . The observed nitrate removal corresponded to the first order reaction kinetic . The data correlation between alkalinity destruction and nitrate nitrogen reduction was linear with a slope of 3 .09 mg -CaCO3 alkalinity destroyed per mg -NO3 N removed . The data correlation between sulfate production and nitrate nitrogen reduction was linear with a slope of 6 .91 mg - produced per mg - removed . Based on the biologically mediated half -reaction equations , the overall reaction equations were developed . Based on the experimental data , the energy coefficients and the stoichiometry of autotrophic denitrification were developed . Finally , an analytical model based on conjugate reaction kinetic was utilized . The reaction rate constants k1 and k2 were determined from the experimental data . The model provides an analytical tool to predict the nitrate and nitrite concentrations in the effluent from the up -flow column . An example is presented to illustrate the design procedure of a sulfur -packed up -flow column . In this example a sulfur -packed up -flow column is designed to treat a given flow rate and influent concentration of nitrate nitrogen to achieve a desired degree of treatment . |