Proof of concept and improvement of a triple chamber biosystem coupling anaerobic digestion, nitrification and mixotrophic endogenous denitrification for organic matter, nitrogen and sulfide removal from domestic sewage

In this study, two versions of a triple chamber biosystem, coupling anaerobic digestion, nitrification and mixotrophic endogenous denitrification (ADNMED), were evaluated and compared. They were designed to maximize the use of endogenous electron donors produced by anaerobic digestion (residual organic matter and sulfide) to abate a portion of the influent nitrogen contained in domestic sewage while removing the inconvenience of effluent sulfide. The first version was able to abate 40% of the influent nitrogen but presented operational and hydrodynamic problems, which resulted in sulfide emissions. A modified second version was proposed, improving the first approach and achieving a nitrogen abatement of more than 60% and a sulfide-free effluent, complying with local emission standards. The results demonstrated that endogenous electron donors produced by anaerobic digestion should not be neglected, and a significant cost reduction in nitrogen removal from domestic sewage could be achieved by exploiting their potential with novel reactor configurations.