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Abstract

An enhanced biological phosphorus removal (EBPR) process is currently one of the most economical and practical ways to reduce high phosphorus content in wastewaters. Under sequential conditions of anaerobic and aerobic environments, the phosphateaccumulating organisms (PAOs), which are able to accumulate intracellular phosphorus in a much higher quantity than other microorganisms, become predominant. In anaerobic stage, the PAOs absorb readily biodegradable substrate by destroying their storage polyphosphate to form adenosine triphosphate (ATP) and adenosine diphosphate (ADP), sequentially, and releasing free phosphate to the bulk solution. The substrate taken up is metabolized in the following aerobic stage to produce energy some of which replenishes the polyphosphate storage pool by absorbing phosphate from the bulk solution. The amount taken up aerobically is more than that released anaerobically; hence the phosphorus in the liquid phase is reduced. Although many researchers have recently attempted to investigate the ecology and microbiology of the EBPR processes using either culture-dependent or -independent approaches, the results are still inconclusive.1 In parallel to microbiologial approach, several investigators have tried to solve this problem through biochemical models which are developed based on mechanistic considerations of the mixed cultures in activated sludge under control conditions. These models, e.g., Comeau model, 2 Mino model, 3 metabolic model, [4][5][6] and enhanced culture kinetic model, 7-9 involve stoichiometry and process kinetic rate equations. Many EBPR systems have been designed and constructed by using the simplified versions of these models. Although most of them perform reliably as expected, some behave unpredictably. One possible explanation of most interest to the researchers is that, under certain operating conditions, other microorganisms are more selectively favored than the PAOs, hence diminishing the EBPR performance. The microbial group believed to be a major competitor of the PAOs are the glycogenaccumulating organisms (GAOs), which also assimilate substrates under anaerobic conditions. 10 As named, this microbial group aerobically synthesizes and stores glycogen as its primary energy source. Since polyphosphate is not involved in substrate assimilation, ABSTRACT: Four anaerobic-aerobic sequencing batch reactors with 9-day of sludge age were operated under a 12-hour cycle of 5, 290, 360, 60, and 5 minutes for the filling, anaerobic, aerobic, settling, and withdrawal periods, respectively. The results indicated that increasing temperature from the phosphate-accumulating organisms (PAOs) preferred temperature of 20°C by either pulse (5°C after every 5 days) or step (1°C per day) manner had negative impacts on the PAOs' activities, particularly on the aerobic phosphorus uptake. However, the pulse-increase scenario, especially from 30 to 35°C, caused more severe impacts than the stepincrease scenario. On the contrary, the shock in a decreasing manner regardless of experimen...

Multi-cycle operation of enhanced biological phosphorus removal (EBPR) with different carbon sources under high temperature

“…However, the P/C ratios in both reactors were higher than models (0.50 and 0.42 P-mol/C-mol) developed under lower temperature (Oehmen et al 2005e, Smolders et al 1994. Panswad et al (2003) also observed that the specific phosphorus release rates increased with the increase of temperature. The higher P/C ratios should be partly due to higher maintenance energy required for PAO at high temperature.…”

“…Previous research demonstrated that the employment of EBPR in tropical climate was challenging due to the proliferation of GAOs when the temperature was higher (25 o C~30 °C) (Lopez-Vazquez et al 2009a, Lopez-Vazquez et al 2009b, Panswad et al 2003, Whang and Park 2006. However, a few successful EBPR processes operated at high temperature have shone some light on the feasibility of high temperature EBPR (Freitas et al 2009, Ong et al 2013, Winkler et al 2011.…”

Microbial synergies and dynamics in biological nutrient removal processes

“…Studies had contradictory results regarding EBPR efficiency and stability at different temperature ranges, but it was widely agreed that low temperature (below 20°C) favored PAO against GAO in many lab-scale studies (Whang and Park, 2002, Panswad et al, 2003, Whang and Park, 2006. Nevertheless, the reason for cold temperature favoring PAO was still under debate (Gebremariam et al, 2011).…”