Post-combustion carbon capture (PCC) wastewater treatment using pre-anoxic denitrification process

Amine-based post-combustion carbon capture (PCC), widely used for CO 2 mitigation, generates amine-rich wastewater containing ammonia and hazardous byproducts, posing environmental challenges. Biological treatment offers a sustainable solution for its management. This study investigated a pre-anoxic denitrification–nitrification system operated in sequencing batch reactors (SBRs) to treat synthetic PCC wastewater containing both monoethanolamine (MEA) and diethanolamine (DEA), representing a more realistic mixture than commonly studied. The system operated at a 2-day hydraulic retention time (HRT) with low organic loading (COD/N ≈ 3.5), without nutrient adjustment (C:N:P ≈ 61:18:1), and influent amine concentrations were gradually increased to 3000 mg/L to simulate real operating conditions. Initial tests used synthetic wastewater formulated from a local PCC plant's contaminant profile. Later, a 5 M MEA-rich pilot-scale stream containing multiple degradation byproducts was diluted into the influent, reaching approximately 10,000 mg/L total amines. Results showed that the system effectively degraded MEA and DEA in the anoxic stage and achieved high ammonium and COD removal at amine concentrations up to 3000 mg/L. However, introducing the real MEA-rich stream exposed process limitations, including incomplete amine biodegradation, nitrite accumulation, and inhibition of nitrite-oxidizing bacteria. Microbial community analysis indicated functional separation between reactors: the pre-denitrification SBR was enriched with amine-degrading denitrifiers (e.g., Thauera , Rhodobacter ), while the nitrification SBR developed an aerobic, carbon-limited community supporting ammonia oxidation. • Pre-anoxic denitrification was evaluated for PCC wastewater treatment containing both MEA and DEA. • Amine levels were increased up to 10,000 mg/L, including real MEA-rich streams. • The system operated under low-COD/high-N conditions without nutrient adjustment. • Introducing a real MEA-rich stream revealed process limitations, including nitrite accumulation and NOB inhibition. • Thauera and Rhodobacter were identified as dominant amine-degrading genera.