Comparative Study on Nitrogen Removal Efficiency of Surface Water by Three New Combined Processes of Autotrophic Denitrification

Abstract

Surface water usually has high dissolved oxygen, low BOD₅ and C/N. In the process of water self-purification, denitrification reaction cannot be carried out due of insufficient carbon source and difficulty in forming anaerobic environment, so it is easy to present nitrate nitrogen pollution. In this study, three new combined processes were proposed to remove nitrogen from high dissolved oxygen micro-pollution surface water: 1) Iron autotrophic denitrification combined with moving bed biofilm reactor (MBBR); 2) Hydrogen autotrophic denitrification combined with MBBR; 3) Hydrogen autotrophic, iron autotrophic denitrification and MBBR combined process, and the nitrogen removal effects of three combined processes were compared. The results showed that ${\text{NO}}_{3}^{-}\text{-N}$ and TN removal rates of iron autotrophic and MBBR combinations, hydrogen autotrophic and MBBR combinations, and iron autotrophic, hydrogen autotrophic and MBBR combinations were 60.9%, 57.1%, 62.1% and 34.3%, 20.5%,35.2%. After laboratory deblocking, the water sample has evaporated more than half, but the removal rate of ${\text{NO}}_{3}^{-}\text{-N}$ and TN increased to 67.5%, 84.3% and 47.5%, 63.9% by iron autotrophic and MBBR combination and iron autotrophic, hydrogen autotrophic and MBBR combination. The research results provide a technical reference for denitrification of high dissolved oxygen micro-polluted surface water.