Integrated urban wastewater management through on-site generation and application of ferrous carbonate

Integrated urban water management is an increasingly popular concept that cost-effectively maximizes system-wide performance by holistically considering all aspects of water and wastewater sectors. An innovative technology enabling production of high-quality bioenergy and an iron salt, ferrous carbonate (FeCO₃), represents a significant opportunity for integrated urban water management. This study experimentally evaluates the effect of in-sewer FeCO₃ dosing on the performance of sewers and the downstream wastewater treatment plants. Two continuous-flow laboratory-scale urban wastewater systems, each consisting of sewer reactors, a sequencing batch wastewater treatment reactor, and an anaerobic digester, were operated in parallel. After establishing comparable performance, one served as the control without any chemical dosing, while the other received a dosing of 10mgFe/L of FeCO₃ in its sewer reactors. Compared to the control, the FeCO₃-dosed experimental system reduced dissolved sulfide concentrations by 32.2±3.3% (at 0.58 ± 0.05 mg S/mg Fe, or 1.0 mol Fe/mol S) in sewer reactors, decreased phosphate concentrations by 38.3% ± 3.2% (at 0.37 ± 0.04 mg P/mg Fe, or 1.5 mol Fe/mol P) in sequencing batch reactors, and lowered dissolved sulfide concentrations by 72.0 ± 4.2% (18.9 ± 2.4 mg S/L) in the anaerobic sludge digester. Iron accumulated in the sludge and improved sludge settleability by 33.9 ± 5.5% and enhanced dewaterability of anaerobically digested sludge by 15.9 ± 2.0%. The findings indicate multiple benefits from the integrated use of FeCO₃, potentially being as a substitute for the currently used iron salts in urban wastewater systems. © 2024 The Author(s).