High-rate nitrogen and phosphorus removal in a sulfur and pyrrhotite modified foam concrete constructed wetland

In order to develop constructed wetland (CW) with high-rate N and P removal, sulfur and pyrrhotite modified foam concrete (SPFC) was prepared and used as a substrate to construct CW (SPFC-CW). At hydraulic retention time 6 h, SPFC-CW achieved effluent total nitrogen (TN) 9.96 mg/L and PO43--P 0.11 mg/L as influent TN and PO43--P were 24.52 and 1.04 mg/L, respectively. TN and PO43--P removal rates of SPFC-CW were 21.8 and 1.4 g/m2d, respectively. Many precipitates with high content of Ca and P attached on SPFC. Sulfurimonas was the most dominant bacterium, and its relative abundances at upper, middle and bottom of SPFC-CW were 53.8 %, 68.4 % and 87.3 %, respectively. SPFC could slowly release Sn2- and S2O32-, which had higher autotrophic denitrification rate than pyrrhotite and sulfur, and more Ca2+ than foam concrete. In SPFC-CW sulfur autotrophic denitrification and Ca-P precipitation were the major N and P removal processes, respectively.