Abstract
Management of phosphorus discharge from human waste is essential for the control of eutrophication in surface waters. Enhanced biological phosphorus removal (EBPR) is a sustainable, efficient way of removing phosphorus from waste water without employing chemical precipitation, but is assumed unachievable in tropical temperatures due to conditions that favour glycogen accumulating organisms (GAOs) over polyphosphate accumulating organisms (PAOs). Here, we show these assumptions are unfounded by studying comparative community dynamics in a full-scale plant following systematic perturbation of operational conditions, which modified community abundance, function and physicochemical state. A statistically significant increase in the relative abundance of the PAO Accumulibacter was associated with improved EBPR activity. GAO relative abundance also increased, challenging the assumption of competition. An Accumulibacter bin-genome was identified from a whole community metagenomic survey, and comparative analysis against extant Accumulibacter genomes suggests a close relationship to Type II. Analysis of the associated metatranscriptome data revealed that genes encoding proteins involved in the tricarboxylic acid cycle and glycolysis pathways were highly expressed, consistent with metabolic modelling results. Our findings show that tropical EBPR is indeed possible, highlight the translational potential of studying competition dynamics in full-scale waste water communities and carry implications for plant design in tropical regions.
Highlights
Temperatures >25 °C, glycogen accumulating organisms (GAOs) can outcompete polyphosphate accumulating organisms (PAOs) for organic carbon[7,8,9,10,11]
The presence of enhanced biological phosphorus removal (EBPR) activity was investigated by subjecting biomass collected from Ulu Pandan Water Reclamation Plant (WRP) to cyclic anaerobic/ aerobic conditions that encourage P release and uptake activity by PAOs
Tropical EBPR has long been considered unfeasible because GAO–organisms will outcompete PAO–organisms for organic carbon at the higher temperatures encountered in tropical conditions[6]
Summary
Temperatures >25 °C, GAOs can outcompete PAOs for organic carbon[7,8,9,10,11]. Higher GAO to PAO proportions were consistently observed in lab-scale reactors operated at 30–35 °C compared to those at 20 °C10,12. Studies conducted on enriched Competibacter–GAO and Accumulibacter cultures showed higher maximum acetate uptake rates of GAOs compared to those of PAOs at temperatures of 20–35 °C7. All of these findings were based on lab–scale enrichment systems, and have far not been verified in full–scale treatment systems. The well-defined operational conditions in lab-scale systems likely eliminated potential ecological niches for the growth of other Accumulibacter clades, putative PAOs and other GAOs20,22. We hypothesized that increased dissolved oxygen concentration will provide a competitive advantage to GAOs over PAOs in full–scale tropical EBPR systems, a view supported by a more recent reactor study showing that excessive aeration suppresses PAOs but will favour the growth of GAOs37.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
