Re-analysis of the Pros and Cons of Sulfur Autotrophic Denitrification Technology
Sulfur autotrophic denitrification (SAD) has attracted increasing attention due to its low cost, no need for external carbon sources, and low sludge production. This review systematically examines the reaction principles and key material elements of various electron donors for SAD, including elemental sulfur, sulfide, thiosulfate, and iron sulfide. It discusses recent research progress on different SAD processes and the influence of environmental factors. A comparative analysis between heterotrophic denitrification and SAD highlights SAD's advantages in reaction rate, secondary pollution, and cost-effectiveness, underscoring its promising application prospects. Notably, iron sulfide-based autotrophic denitrification maintains stable pH and produces fewer by-products (e.g., sulfate, nitrous oxide). When developed into an aggregate sulfur concrete system, it can purify nitrogen and phosphorus from secondary effluent standards to Class IV surface water standards within a hydraulic retention time of only 0.5–2 hours, addressing the contradiction between SAD reaction rate and engineering demands. This enables efficient simultaneous nitrogen and phosphorus removal, making it viable for groundwater remediation, advanced wastewater treatment, eutrophication control, and deep nitrogen removal. The national 'Dual Carbon Strategy' (carbon neutrality and peak) positions SAD as a promising method for wastewater treatment plants to meet increasingly stringent nitrogen and phosphorus discharge standards.