Sidestream bio‐P and mainstream anammox in a BNR process with upstream carbon capture

Abstract

AbstractThe integration of biological phosphorus removal (bio‐P) and shortcut nitrogen removal (SNR) processes is challenging because of the conflicting demands on influent carbon: SNR allows for upstream carbon diversion, but this reduction of influent carbon (especially volatile fatty acids [VFAs]) prevents or limits bio‐P. The objective of this study was to achieve SNR, either via partial nitritation/anammox (PNA) or partial denitrification/anammox (PdNA), simultaneously with biological phosphorus removal in a process with upstream carbon capture. This study took place in a pilot scale A/B process with a sidestream bio‐P reactor and tertiary anammox polishing. Despite low influent rbCOD concentrations from the A‐stage effluent, bio‐P occurred in the B‐stage thanks to the addition of A‐stage WAS fermentate to the sidestream reactor. Nitrite accumulation occurred in the B‐stage via partial denitrification and partial nitritation (NOB out‐selection), depending on operational conditions, and was removed along with ammonia by the tertiary anammox MBBR, with the ability to achieve effluent TIN less than 2 mg/L.Practitioner Points A sidestream reactor with sufficient fermentate addition enables biological phosphorus removal in a B‐stage system with little‐to‐no influent VFA. Enhanced biological phosphorus removal is not inhibited by intermittent aeration and is stable at a wide range of process SRTs. Partial nitritation and partial denitrification are viable routes to produce nitrite within an A/B process with sidestream bio‐P, for downstream anammox in a polishing MBBR.