Towards mainstream deammonification of municipal wastewater: Partial nitrification-anammox versus partial denitrification-anammox.

The mainstream deammonification has been believed as a viable technology for the energy-neutral municipal wastewater treatment, which can be realized through two approaches known as partial nitrification-anammox (PN/AMX) and partial denitrification-anammox (PDN/AMX). However, large-scale applications of these deammonification processes for municipal wastewater treatment have been rarely reported thus far. Given such a situation, this review examined the mainstream PN/AMX and PDN/AMX processes with the focus on their engineering feasibility, economic viability and potential challenges. It was revealed that soluble COD and stable nitrite production were the main challenges for mainstream deammonification. Pre-capture of COD was essential for mitigating the competition between denitrifiers and anammox bacteria on nitrite, while NOB suppression and partial denitrification control to nitrite stage were critical issues for stable nitrite production in PN and PDN processes respectively. Compared to nitrification-denitrification, the unit oxygen demand for nitrogen removal in PN/AMX and PDN/AMX could be reduced by 57.3% and 47.7%, while the sludge production could also be cut off by 83.7% and 66.3% in PN/AMX and PDN/AMX respectively. These clearly showed the greater economic viability and environmental sustainability of PN/AMX against PDN/AMX. Consequently, more effort is needed to improve the engineering feasibility of large-scale mainstream deammonification for municipal wastewater treatment.