해수조건에서 황을 전자공여체로 이용하는 자가영양 탈질 효율에 대한 S/N비와 초기 pH의 영향

Abstract

Most denitrification studies have tested carbon based heterotrophic denitrification in freshwater conditions, which result in excessive bacterial biomass over the denitrification process. This study evaluated the performance of sulfur based autotrophic denitrification with different sulfur/nitrogen (S/N) ratios and initial pHs in the seawater condition. Experimental S/N ratios in the first experiment were 0.2, 0.7, 1.2, 1.7, 2.2 and 2.7 in the mole basis. Daily removal rates of nitrate-N ranged 248~257 g/m3·day-1 at S/N ratios of over 1.7, showing no differences among the treatments. In addition, the produced sulfate (the end-product of sulfur) per removed nitrate-N increased with increasing S/N ratio, indicating that more electron donors were used to remove the same amount of nitrate-N. Also, concentrations of total ammonia nitrogen and nitrite-nitrogen were not significantly different among the treatments over S/N ratio of 1.7 (P>0.05). Experimental initial pHs used in the second experiment were set at 5, 6, 7, 8 and 9. The removal rate of nitrate-N was highest (235 g/m3·day-1) at the initial pH of 8, decreasing at the higher or lower initial pHs. In conclusion, the optimum S/N ratio and initial pH or autotrophic denitrification using thiosulfate as an electron donor were found at 1.7 and 8, respectively.