Infuse

Phosphorus (P) is a pollutant in surface waters but also a nonrenewable resource. Enhanced biological phosphorus removal (EBPR) is a process widely employed for P removal in municipal wastewater treatment plants (WWTPs), because it is relatively cheap and sustainable and desirable for downstream nutrient recovery. Despite the advantages, its application in warm climates has long been considered unfavorable, owing to observations that the functional polyphosphate accumulating organisms (PAOs) in the process were outcompeted by glycogen accumulating organisms (GAOs) at high temperatures. In contrast, we demonstrate stable EBPR in full-scale systems operating at water temperatures of 28–32◦C in Singapore, despite the presence of GAOs. A recent field study revealed a wide range of PAOs exhibiting high micro-diversity in carbon usage, which may explain the observed EBPR stability in these WWTPs. We also demonstrate the long-term feasibility of EBPR at 35◦C in a lab-scale reactor. Diverse and abundant Candidatus Accumulibacter amplicon sequence variants are closely related to those found in temperate environments, suggesting that EBPR at higher temperatures does not require a highly specialized PAO community. In general, a slow-feeding strategy and sufficiently high carbon input effectively limits the carbon uptake rates of GAOs at elevated temperatures, representing basic conditions suitable for full-scale treatment plants experiencing higher water temperatures.

Reclaimed water is an important source of water globally. Typically, the recovery of water reclamation process by membrane technology, i.e., microfiltration/ultrafiltration-membrane bioreactor (MF/UF-MBR) and reverse osmosis (RO), is limited to 75-80% due to fouling of RO membrane. In this work, a hybrid nanofiltration-membrane bioreactor + reverse osmosis (NF-MBR+RO) process was developed to achieve ≥90% of recovery in water reclamation. The novel low-pressure hollow fiber NF membrane only requires an operating pressure of <2 bar, possesses a positively charged selective layer, molecular weight cut off (MWCO) of <500 Da, and rejection of Mg2+ and Ca2+ is at ~90%. It has very low rejection of Na+ ions (<15%) while maintaining high rejection of the divalent ions, which is the key to achieve such a low operating pressure condition. The results showed that the NF-MBR achieved superior permeate quality (i.e., TOC < 2 mg/L) due to enhanced biodegradation and excellent rejection properties of the NF membrane, leading to high RO recovery rate of ≥90% (i.e., compared to 75% in conventional UF-MBR permeate as RO feed). Furthermore, the salt accumulation (i.e., build-up of divalent ions) observed in the NF-MBR did not have negative impact on the organics removal efficiency and biomass viability.