Date of Award
Master of Science (MS)
Civil & Environmental Engineering
Charles B. Bott
It is well known that soluble organic carbon (sCOD), especially in the form of volatile fatty acids (VFA), is critical to achieving reliable enhanced biological phosphorus removal (EBPR) in biological nutrient removal (BNR) processes. Consistent and reliable EBPR in systems treating wastewaters deficient in sCOD may be accomplished by the addition of VFA and sCOD – rich fermentate produced by the fermentation of primary sludge, return / waste activated sludge (RAS / WAS), or other suitable carbon sources. The solids retention time (SRT) of fermenters being used to supplement carbon in sidestream EBPR processes must be controlled such that complex organics are hydrolyzed into simpler fractions, which are then converted into soluble organic carbon, including but not limited to short chain VFAs (i.e. SCVFA) via acidogenesis and acetogenesis, while also preventing methanogenesis from occurring (Skalsky and Daigger, 1995).
Perhaps the most widely employed sidestream EBPR processes involve sidestream RAS fermentation using several different configurations (J. Barnard et al., 2010; Vollertsen et al., 2006). These systems typically divert 5 – 30% of the RAS flow in an activated sludge process to an anaerobic, sidestream bioreactor, with hydraulic residence times (HRTs) in the range of 16 – 48 h. These HRTs may be reduced by the addition of supplemental carbon derived from the fermentation of a portion of the primary sludge. While there are several papers available in the literature detailing the operation and optimization of fermenters fed with primary sludge, little information is available about the performance of fermentation processes that employ sludge generated in high rate activated sludge (HRAS) systems. This study was carried out at a pilot plant operating an A/B type process and involved fermentation of a portion of the WAS from a HRAS A-stage process to add soluble carbon to a sidestream EBPR process receiving a portion of the RAS from B-stage. The goal was to achieve biological phosphorus removal and optimize performance in the sidestream reactor while utilizing supplemental carbon from the A-stage WAS fermenter.
Ferguson, Lindsey E..
"Sidestream RAS Fermentation for Stable Bio-P Combined with Short Cut Nitrogen Removal in an A/B Process"
(2019). Master of Science (MS), Thesis, Civil & Environmental Engineering, Old Dominion University, DOI: 10.25777/qeqm-2n59