The Biological Denitrification Using Ferric Hydroxide Desulfurized Waste as an Electron Donor

This study aimed to investigate the feasibility of using iron-rich ferric hydroxide desulfurized waste (FHDW) as an alternative electron donor for biological denitrification, with the objective of diverting it from landfill disposal. By harnessing the potential of the FHDW as the electron donor, we can effectively offset landfill costs while simultaneously mitigating environmental pollution.

Batch and lab-scale up-flow column tests were conducted. The batch experiment was conducted in a 500 mL media bottle, using 200 mL FHDW and 250 mL synthetic wastewater. For the column test, two plastic reactors having an internal diameter of 3.8 cm and a height of 21 cm were established. Column I was filled with FHDW (240 mL), and column II with S⁰ (240 mL), and operated at different empty bed contact times (EBCTs).

Both the batch and column test results confirmed the possibility of using FHDW as an electron donor for biological denitrification. The batch test achieved 100% nitrogen removal in 5 days of operation. The highest denitrification activity was observed in column I, achieving 100% nitrate reduction at 16 and 8 h EBCTs, and the denitrification activity reduced significantly as the EBCT shortened. Column II exhibited the lowest denitrification performance compared to the FHDW-based denitrification system. The FHDW-based denitrification system produced alkalinity so no buffer addition was needed.

This study confirmed the feasibility of using FHDW as an electron donor in a biological denitrification system. Utilizing desulfurized waste as an electron donor, we can achieve the dual benefit of alleviating financial burdens associated with landfilling and reducing environmental pollution.