[Substrate Flow by Different Biochemical Activities in the Urban Sewage Network].

In order to investigate the consumption mechanism of organic contaminants in different biological metabolism pathways within an urban sewage network, a pilot-scale system using two kinds of sediments (urban sewage sediment and artificial sediment) was constructed. The pilot system was operated to study the migration and transformation characteristics of COD, methane, nitrate, and sulfate between sediment and sewage. Results showed that the variation of COD in sewage was 170.58 mg·L-1, with change of COD by deposition and bioreaction of 101.53 mg·L-1 and 69.05 mg·L-1, respectively. Due to biological metabolism, the generation of methane in sewers was of 7.39 mg·L-1; the decrease of nitrate and sulfate in sewage was 0.33 mg·L-1 and 21.35 mg·L-1, respectively. Based on our calculations, the consuming concentration of COD was 32.51 mg·L-1for methane generation, 8.04 mg·L-1 for denitrification, and 6.41 mg·L-1for sulfate degradation by sulfate reducing bacteria. The decrease in COD by deposition was responsible for 65.38% of total variation of COD in sewage. The decrease in COD by bioreaction was responsible for 34.62% of total variation in COD. Meanwhile, total variation values of COD for methane generation, denitrification, and sulfate degradation were responsible for 68.01% of COD variation by bioreaction. Deposition was therefore the main pathway for removal of organic contaminants from the sewer system; biochemical activities of methane generation, denitrification, and sulfate degradation also played important roles.