Re-analysis of the Pros and Cons of Sulfur Autotrophic Denitrification Technology

• • Iron sulfide-based autotrophic denitrification achieves stable pH and reduces by-product formation (e.g., sulfate, nitrous oxide), with a hydraulic retention time of only 0.5–2 h to purify secondary effluent to Class IV surface water standards, enabling efficient simultaneous nitrogen and phosphorus removal. • • SAD eliminates the need for external carbon sources, reducing operational costs and sludge production compared to heterotrophic denitrification, as evidenced by pilot-scale studies (e.g., sulfur-limestone biofilter achieving high nitrate removal). • • The use of pyrite (FeS2) as an electron donor in autotrophic denitrification has been shown to effectively remove nitrate and phosphate simultaneously, with studies demonstrating enhanced performance in constructed wetlands and vertical-flow biofilters. • • SAD technology aligns with the 'Dual Carbon Strategy' by offering a low-carbon approach for deep nitrogen removal, addressing the bottleneck of meeting stringent nitrogen and phosphorus discharge standards in wastewater treatment plants.