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Column Studies on Nitrate Removal from Potable Water |
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| Authors: | A Darbi T Viraraghavan R Butler D Corkal |
| Institution: | 1. Faculty of Engineering, University of Regina, Regina, Saskatchewan, Canada 2. Faculty of Engineering, University of Regina, Regina, Saskatchewan, Canada (author for correspondence 3. Water Quality Engineer, PFRA, Winnipeg, Manitoba, Canada 4. Water Quality Research Coordinator, PFRA, Saskatoon, Saskatchewan, Canada |
| Abstract: | Biological processes can achieve nitrate removal from groundwater. The sulfur/limestone autotrophic denitrification by Thiobacillus denitrificans was evaluated with three laboratory-scale column reactors. The optimum sulfur/limestone ratio was determined to be 2:1 (mass/mass). Different hydraulic retention times were used during the column tests to examine nitrate removal efficiencies. Under an HRTs of 13 h, nitrate concentration of 60 mgNO3 --N L-1 was reduced to less than 5 mg NO3 --N L-1. On a higher HRT of 26 h the nitrate removal efficiency was close to 100% for all nitrate-nitrogen loading rates. Different initial nitrate-nitrogen concentrations (30, 60, and 90 mg NO3 --N L-1) were used in the study. Column tests showed that the nitrate-nitrogen loading rate in this study was between 50 to 100 g NO3 --N m-3 d-1 to obtain a removal efficiency of 80–100%. It was found that approximately 6 mg SO4 2- was produced for 1 mg NO3 --N removed. Nitrite-nitrogen in all cases was less than the maximum allowable concentration of 1 mg NO2 --N L-1. Effluent pH was stable in the range of 7 to 8; the effluent dissolved oxygen was less than 0.15 mg L-1 and the oxidation-reduction potential in all columns was in the range of –110 to –250 mV. |
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