Fermentation of Mixed Liquor for Phosphorus Removal

Abstract

All discoveries associated with phosphorus removal were first made in plants as accidental occurrences. Once observed, they were followed by laboratory and pilot scale work to be studied and explained. While the mechanism of biological phosphorus removal has been well researched and documented to the point where it is now possible to design a plant with a very reliable phosphorus removal process using formal flow sheets, biological phosphorus removal is still observed in a number of plants that have no designated anaerobic zone, which is considered essential for phosphorus removal. It was also not possible to model all these plants with standard simulation packages such as BioWin and GPS-X. This paper will discuss some of the background, and some case histories and applications, and present a simple postulation as to the mechanism and efforts at modeling the results.

Survey of full‐scale sidestream enhanced biological phosphorus removal (S2EBPR) systems and comparison with conventional EBPRs in North America: Process stability, kinetics, and microbial populations

“…Based on operating data from full‐scale and pilot‐scale operations of the process, it appears that a reduction in effluent PO 4 –P concentrations can be realized using the UMIF operation. During a pilot test at the Pinery Water Facility in Colorado, the average secondary effluent TP concentration was less than 0.5 mg P/L, without chemical addition (Barnard et al, ). The intermittent mixing operation at this facility resulted in an estimated SRT in the UMIF reactor of approximately 3 days (Barnard, Dunlap, & Steichen, ).…”

“…S2EBPR refers to modified EBPR configurations that include diversion of a portion of RAS or anaerobic mixed liquor to a sidestream reactor, where VFA production via sludge fermentation and PAO activity-related P release and carbon uptake occur. S2EBPR has proven successful at a number of facilities worldwide; currently, there are about 80 full-scale facilities that have implemented various forms of the S2EBPR process (Barnard, Houweling, Analla, & Steichen, 2010;Copp, Belk, & Vale, 2012;Stevens, Ellsworth, Wyman, & Lambrecht, 2015;Stroud & Martin, 2001;Vale, Barnard, Thomas, & Dold, 2008;Vollertsen, Petersen, & Borregaard, 2006). A few recent studies that compared EBPR activities, rates, and microbial populations between S2EBPR and conventional EBPR facilities suggested observable differences between the two configurations (Lanham, Oehmen, et al, 2013a;Mielczarek, Nguyen, Nielsen, & Nielsen, 2013;Stokholm-Bjerregaard et al, 2017).…”

Activated Sludge – 100 Years and Counting

“…The excellent performance of the plant ceased when the pilot was reconfigured and there was no longer a connection between the two zones. Barnard et al (2010) used this technique to improve P removal in the Henderson, Nevada, USA plant, which had no primary settling tanks. In the basic Bardenpho plant, they passed the RAS through an anoxic zone and then through an anaerobic stage with a portion of the RAS being fermented and returned to the anaerobic zone.…”

Fundamentals of Sludge Fermentation for Enhanced Biological Phosphorus Removal

“…The secondary process was not designed to remove phosphorus, but when vapor-phase odor control was added and chlorination stopped, the plant removed phosphorus to low levels even with only anoxic zones. At the Henderson NV plant (Barnard et al 2010) there was sufficient VFA in the influent during the design phase but a subsequent introduction of nitrates for odor control reduced the influent VFA to less than 5 mg/L which resulted in the loss of phosphorus removal. This was recovered by using mixed liquor fermentation as will be described later.…”

“…No nitrification took place in this process. Barnard et al (2010) proposed fermentation of a portion of the mixed liquor from the anaerobic zone and then return it to the anaerobic zone.…”