Effective utilization of refractory dissolved organic matters in domestic sewage allows to enhanced nitrogen removal by integrated fermentation, nitrification, denitratation and anammox process

To take full advantage of refractory dissolved organic matters (rDOMs) and generate sufficient nitrate for domestic sewage treatment, this study presented a novel integrated fermentation, nitrification, denitratation and anammox (IFNDA) process in a combined ABR-CSTR reactor. The results showed that an advanced total nitrogen (TN) removal efficiency of 94.1% was obtained after over 190 days operation, resulting in effluent TN concentration as low as 3.6 mg/L. The system nitrogen removal was dominated by anammox with a high proportion of 88.6%. The high conversion rate of acetic acid (54.0%) and volatile fatty acids (64.5%) from rDOMs in domestic sewage by in-situ fermentation drove efficient denitratation. Microflora analysis indicated that the enriched Commamonas (3.5%) and Longilinea (3.3%) dominated hydrolysis and acidogenesis of organics, and Methanosaeta (9.0%) obligated acetoclastic methanogenesis in two-stage fermentation process. Thauera (8.4%) and Candidatus Brocadia (2.5%) were the core bacteria for nitrogen metabolism in the IFNDA system.