The occurrence of enhanced biological phosphorus removal in a 200,000 m3/day partial nitration and Anammox activated sludge process at the Changi water reclamation plant, Singapore

Abstract

Mainstream partial nitritation and Anammox (PN/A) has been observed and studied in the step-feed activated sludge process at the Changi water reclamation plant (WRP), which is the largest WRP (800,000 m/d) in Singapore. This paper presents the study results for enhanced biological phosphorus removal (EBPR) co-existing with PN/A in the activated sludge process. Both the in-situ EBPR efficiency and ex-situ activities of phosphorus release and uptake were high. The phosphorus accumulating organisms were dominant, with little presence of glycogen accumulating organisms in the activated sludge. Chemical oxygen demand (COD) mass balance illustrated that the carbon usage for EBPR was the same as that for heterotrophic denitrification, owing to autotrophic PN/A conversions. This much lower carbon demand for nitrogen removal, compared to conventional biological nitrogen removal, made effective EBPR possible. This paper demonstrated for the first time the effective EBPR co-existence with PN/A in the mainstream in a large full-scale activated sludge process, and the feasibility to accommodate EBPR into the mainstream PN/A process. It also shows EBPR can work under warm climates.

Toward Energy Neutrality in Municipal Wastewater Treatment: A Systematic Analysis of Energy Flow Balance for Different Scenarios

“…The COD residual was recirculated from the ANAMMOX zone into an anoxic tank (minimum aeration), to facilitate denitrification and the uptake of phosphorus. 53 However, the per capita electricity consumption data of the whole treatment system have yet to be reported from the onsite data. In this treatment process (Figure 2b), the ANAMMOX functional bacteria reproduce at a fairly slow rate (e.g., <0.03 day −1 ), 54 which corresponds to a sludge retention time (SRT) of one month.…”

“…However, so far, very few cases of existing large-scale mainstream ANAMMOX treatment systems in operation, such as the Changi Water Reclamation Plant in Singapore, appear to have been unaffected by the transfer of soluble COD to the ANAMMOX system. The COD residual was recirculated from the ANAMMOX zone into an anoxic tank (minimum aeration), to facilitate denitrification and the uptake of phosphorus . However, the per capita electricity consumption data of the whole treatment system have yet to be reported from the on-site data.…”

Emerging biological processes for municipal wastewater treatment

“…However, it should also be realized that the observed nitrogen removal was likely enhanced by conventional heterotrophic denitrification in consideration of the high influent C/N ratio. For example, conventional denitrification contributed to 44.6% of the total nitrogen removal in the Changi WRP (Cao et al, 2017b). Obviously, more work is needed to convincingly demonstrate the feasibility and long-term stability of deammonification for treating municipal wastewater.…”

Global warming readiness: Feasibility of enhanced biological phosphorus removal from wastewater at 35°C

“…In addition to these laboratory-scale studies, which included either special process operation control or the presence of a specifically enriched bacterial PAO community, there are reports of stable EBPR in full-scale systems in warm climates (Sayi-Ucar et al, 2015; Law et al 2016; Cao et al, 2017). The presence of both GAOs and PAOs had no apparent effect on long-term stability of EBPR at 30°C (Law et al, 2016).…”