Inducement mechanism and control of self-acidification in elemental sulfur fluidizing bioreactor

The sulfur fluidizing bioreactor (S0FB) has significant superiorities in treating nitrate-rich wastewater. However, substantial self-acidification has been observed in engineering applications, resulting in frequent start-up fail-ures. In this study, self-acidification was reproduced in a lab-scale S0FB. It was demonstrated that self -acidification was mainly induced by sulfur disproportionation process, accounting for 93.4 % of proton gener-ation. Supplying sufficient alkalinity to both the influent (3000 mg/L) and the bulk (2000 mg/L) of S0FB was essential for achieving a successful start-up. Furthermore, the S0FB reached 10.3 kg-N/m3/d of nitrogen removal rate and 0.13 kg-PO43-/m3/d of phosphate removal rate, respectively, surpassing those of the documented sulfur packing bioreactors by 7-129 times and 26-65 times. This study offers a feasible and practical method to avoid self-acidification during restart of S0FB and highlights the considerable potential of S0FB in the treatment of nitrate-rich wastewater.

Automated summary

This study investigates the advantages and problems of sulfur fluidizing bioreactor (S0FB) in treating nitrate-rich wastewater. It reveals that self-acidification is the main problem and can be addressed by providing sufficient alkalinity. The experimental results show that S0FB has higher nitrogen and phosphate removal rates compared to conventional sulfur packing bioreactors.