Synergetic effects of pyrrhotite and biochar on simultaneous removal of nitrate and phosphate in autotrophic denitrification system

Abstract

In the trend of upgrading wastewater treatment plants, developing advanced treatment technologies for more efficient nutrient removal is crucial. This study prepared a pyrrhotite‐biochar composite (FexSy@BC) to investigate its potential for simultaneous removal of nitrate and phosphate under autotrophic denitrification conditions. X‐ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), and X‐ray photoelectron spectroscopy (XPS) were used to characterize the novel composite of FexSy@BC, which exhibited 9.2 mg N/(L·d) NO3−‐N reduction rate, 97.3% N2 production, and 81.8 mmol N/(kg·d) NO3−‐N material load with small solid/liquid ratio (0.008). The NO3−‐N removal with FexSy@BC was 1.2–2.2 times higher than that with pure iron sulfides or biochar or their mixtures, whereas the Δn(S)/Δn(N) of FexSy@BC was the lowest (1.80). Moreover, the PO43−‐P reduction rate of FexSy@BC reached 3.23 mg P/(L·d), as high as that of pure pyrite or pyrrhotite. Thiobacillus was the most dominant denitrifying bacterium. FexSy@BC exhibited great promise for enhancing nutrient removal from secondary effluent without additional carbon source. Practitioner Points FexSy@BC enhanced nitrate and phosphate removal simultaneously. First‐order kinetics and Monod model were fitted for denitrification with FexSy@BC. FexSy@BC had smaller molar ratio of sulfate release to nitrate removal. Thiobacillus was the dominant bacterium in FexSy@BC autotrophic denitrification. Synergistic effects on nutrients removal existed between biochar and pyrrhotite.

Removal of Nitrate Nitrogen from Municipal Wastewater Using Autotrophic Denitrification Based on Magnetic Pyrite

“…At present, the research on magneto pyrite autotrophic denitrification is emerging [38][39][40], as a new autotrophic biological denitrification process can effectively achieve the denitrification of synthetic wastewater, surface water, municipal sewage and other denitrification treatments, but due to the high concentration of the influent water, the bioaugmentation time for autotrophic denitrifying bacteria, resulting in a relatively long hydraulic retention time, slower denitrification and the production of a certain amount of SO 4…”

Optimizing phosphate removal by manipulating manganese and cobalt levels in soil aquifer treatment system

“…Filtration through the soil media physically traps and retains larger particles, including particulate forms of PO4 3-. Redox reactions, particularly in anaerobic zones, lead to the precipitation of iron and manganese phosphates, aiding in PO4 3removal (Zhang et al, 2023). Vegetation uptake further enhances PO4 3removal by plants and their root systems (Jacklin et al, 2022).…”