Organic carbon removal from wastewater by a PHA storing biofilm using direct atmospheric air contact as oxygen supply

Abstract

Flavigny, R.M.G. and Cord-Ruwisch, R. (2015) OrganicThis is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. The principal reason for the high energy costs for biological wastewater treatment is the poor transfer efficiency of oxygen to the bulk water phase. The current paper describes a biofilm reactor in which oxygen transfer to the bulk solution is avoided by alternating anaerobic submersed (2h) and drained (1 h) operation of the biofilm. During the submersed phase the biofilm enriched for glycogen accumulating organism (GAO) stored the organic carbon (acetate) as poly-hydroxy-alkanoate (PHA). After draining the reactor, this carbon stored as PHA was biologically oxidised, using oxygen directly from the atmosphere. The 12 Cmmol/L (384 mg/L BOD) of acetate was completely removed during long term automated operation of the reactor for 9 months with a cycle length of 3.3 hours. As the process specifically removes dissolved organic carbon but not N or P it could possibly be coupled with novel processes such as Anammox or nutrient recovery.

Direct oxygen uptake from air by novel glycogen accumulating organism dominated biofilm minimizes excess sludge production

“…The BOD removal performance remained steady for about five months of continuous operation with about 7 cycles per day. This result is in accordance with the observation reported by Flavigny and Cord-Ruwisch (2015).…”

“…On the other hand, Candidatus competibacter the most abundant genus in the matured biofilm samples is a known glycogen accumulating organism (GAO) (Yi et al, 2017). The stable organic carbon removal performance of the described biofilm system is attributed to the predominance of GAO in the biofilm which is in accordance with previous reports (Flavigny and Cord-Ruwisch, 2015;Hossain et al, 2017). Although the relative abundance of Candidatus competibacter decreased from 48.7% (day 56) to 35.1% (day 140), there was no significant effect of their reduction on the carbon removal performance of the biofilm system (Fig.…”

“…Further, the observed sludge yield described in this study is significantly lower than that of other biofilm processes found in literature (Table 1). Hence, next to the previously described benefits in saving 60-75% aeration energy (Flavigny and Cord-Ruwisch, 2015; a Synthetic wastewater used in all these studies.…”

Ecosystem activation system (EAS) technology for remediation of eutrophic freshwater

“…The anoxic stage was operated as an open-mouthed biological filter bed. Polyhydroxyalkanoate (PHA) can not only serve as easy-consuming carbon source for microorganism but also the specific activating reagent only for nitrifying-denitrifying bacteria and phosphorus-accumulating bacteria in conditions where exogenous N and P are lacking 14–16 . If PHA is artificially added to the water, it can specifically favor the reproduction of whole microbial community and beneficial nitrifying-denitrifying bacteria and P-accumulating bacteria 17 .…”

“…If PHA is artificially added to the water, it can specifically favor the reproduction of whole microbial community and beneficial nitrifying-denitrifying bacteria and P-accumulating bacteria 17 . In this study, PHA particles, with a size range of 5–10 mm, were chosen both as biofilm carriers in the anoxic stage and as an activating reagent for the promotion of the growth of the microbial community with specific physiological functions, including nitrifying and denitrifying, and phosphorus accumulation based on previous test results 14–17 . The fill amount of PHA particles was 2/3 the volume of the anoxic stage.…”