Evaluation of alternative electron donors for denitrifying moving bed biofilm reactors (MBBRs)

Abstract

The effectiveness of four different electron donors, specifically methanol, ethanol, glycerol, and sulfide (added as Na(2)S), were evaluated in post-denitrifying bench-scale moving bed biofilm reactors (MBBRs). With the requirement for more wastewater treatment plants to reach effluent total nitrogen levels approaching 3 mg/L, alternative electron donors could promote more rapid MBBR startup/acclimation times and increased cold weather denitrification rates compared to methanol, which has been most commonly used for post-denitrification processes due to low cost and effectiveness. While the application of alternative substrates in suspended growth processes has been studied extensively, fixed film post denitrification processes have been designed to use primarily low yield substrates like methanol. Bench-scale MBBRs were operated continuously at 12 degrees Celsius, and performance was monitored by weekly sampling and insitu batch profile testing. Ethanol and glycerol, though visually exhibited much higher biofilm carrier biomass content, performed better than methanol in terms of removal rate (0.9 and 1.0 versus 0.6 g N/m(2)/day, respectively.) Maximum denitrification rate measurements from profile testing suggested that ethanol and glycerol (2.2 and 1.9 g N/m(2)/day, respectively) exhibited rates that were four times that of methanol (0.49 g N/m(2)/day.) Sulfide also performed much better than either of the other three electron donors with maximum rates at 3.6 g N/m(2)/day and with yield (COD/NO(3)-N) that was similar to or slightly less than that of methanol.

Modeling Glycerol Acclimated Biomass: Using BioWin Add-On to Model the Nitrite Lock

“…Bill, 2009, Uprety, 2012 showed similar responses to what was observed at the 26 th Ward WWTP. The key behavior to be accounted for by the model is summarized below:…”

Moving Bed Biofilm Reactor Technology: Process Applications, Design, and Performance

“…Denitrification. Denitrification in an MBBR has been studied extensively by Aspegren et al (1998), Bill et al (2009), Mases et al (2010), Rusten et al (1996), and Rusten, Hem, and Ødegaard (1995b). The rate of denitrification in an MBBR is influenced by the biofilm area, type of external carbon source, bulk-liquid carbon-to-nitrogen ratio (C:N), wastewater temperature, bulkliquid dissolved oxygen concentration, and bulk-liquid macronutrient concentrations.…”

Biofilm Fixed Film Systems

“…Bill et al [71] did research to evaluate the effectiveness of four different electron donors, specifically methanol, ethanol, glycerol and sulfide in post-denitrifying bench-scale MBBRs. Maximum denitrificaion rate measurements from profile testing suggested that sulfide, ethanol and glycerol substrates exhibited rates greater than methanol.…”