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The Mechanism of Enhanced Biological Phosphorus Removal Washout and Temperature Relationships
Author(s) -
Erdal Ufuk G.,
Erdal Zeynep K.,
Randall Clifford W.
Publication year - 2006
Publication title -
water environment research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.356
H-Index - 73
eISSN - 1554-7531
pISSN - 1061-4303
DOI - 10.2175/106143006x101737
Subject(s) - enhanced biological phosphorus removal , washout , chemistry , phosphorus , anaerobic exercise , zoology , wastewater , biochemistry , chromatography , environmental engineering , activated sludge , biology , medicine , environmental science , organic chemistry , physiology
In this study, the combined effects of temperature and solids retention time (SRT) on enhanced biological phosphorus removal (EBPR) performance and the mechanism of EBPR washout were investigated. Two pilot‐scale University of Cape Town (South Africa) systems fed with synthetic wastewater were operated at 5 and 10°C. The results showed that the phosphorus removal performance was optimum at total SRT ranges of 16 to 24 days and 12 to 17 days for 5 and 10°C, respectively, and steady‐state phosphorus removal was greater at the lower temperature. Higher SRT values of up to 32 days at 5°C and 25 days at 10°C slightly reduced EBPR performance as a result of increased extent of endogenous respiration, which consumed internally stored glycogen, leaving less reducing power for poly‐hydroxy alkanoate (PHA) formation in anaerobic stages. The phosphorus‐accumulating organism (PAO) washout SRTs of the systems were determined as 3.5 days at 5°C and 1.8 days at 10°C, considerably less than the washout SRTs of nitrifiers. Polyphosphorus, the main energy reserve of the EBPR bacterial consortium, was not completely depleted, even at washout points. The inability of EBPR biomass to use glycogen to generate reducing power for PHA formation was the major reason for washout. The results not only suggest that glycogen mechanism is the most rate‐limiting step in EBPR systems, but also that it is an integral part of EBPR biochemistry, as proposed originally by Mino et al. (1987), and later others (Pereira et al., 1996, Erdal et al., 2002; Erdal, Z. K., 2002). The aerobic washout SRT values (2.1 and 1.2 days for 5 and 10°C, respectively) of this study did not fit the linear line for PAO washout developed by Mamais and Jenkins (1992). Perhaps this was because the feeds used during this study were chemical‐oxygen‐demand‐limited (acetate‐based synthetic feed), whereas the feeds used for their study were phosphorus‐limited (external acetate added to domestic wastewater), resulting in different ratios of PAOs and nonPAOs in the biomass.