Characterizing denitrification kinetics at cold temperature using various carbon sources in lab-scale sequencing batch reactors

Abstract

Wastewater treatment plants in the Chesapeake Bay region are becoming more interested in external carbon sources for denitrification. This is in response to the recent regulations to remediate the Chesapeake Bay, which will limit effluent total nitrogen to near 3 mg/L for plants, thus requiring near complete elimination of inorganic nitrogen species. Since sufficient internal carbon is usually not available for complete denitrification, external carbon is needed to supplement internal sources. Of particular interest is the use of an alternate external carbon source to replace the least expensive source methanol. This study focuses on three commonly available external carbon sources: methanol, ethanol and acetate. The aim of this study was to obtain the specific denitrification rate (SDNR) of the substrates under several conditions. Sequencing batch reactors (SBRs) were set up to first grow biomass to the specified substrate while in situ SDNRs were conducted concurrently. Once the biomass was grown with the corresponding substrate, a series of ex situ SDNRs were performed using various biomass/substrate combinations to evaluate response to substrate combinations at 13 degrees C. Results from this study indicate that the SDNRs for biomass grown on methanol, ethanol and acetate were 9.2 mg NO(3)-N/g VSS/hr, 30.4 mg NO(3)-N/gVSS/hr and 31.7 mg NO(3)-N/g VSS/hr, respectively, suggesting that acetate and ethanol were equally effective external carbon sources followed by much lower SDNR using methanol. Ethanol could be used with methanol biomass with similar rates as that of methanol. Additionally, methanol was rapidly acclimated to ethanol grown biomass suggesting that the two substrates could be interchanged to grow respective populations with a minimum lag period.

Enhancing denitrification using a carbon supplement generated from the wet oxidation of waste activated sludge

“…Even though methanol produced the highest increase in SDR with the methanol-acclimated biomass (7 ± 0.3 mg NO 3 gVSS À1 hour À1 ) it was still low compared to other SDRs. Similarly, Mokhayeri et al (2008) found that ethanol could be used with methanol biomass with similar rates to that achieved with methanol. However, Mokhayeri et al (2008) also found ethanol-grown biomass responded rapidly to methanol, suggesting that the two substrates could be used interchangeably to grow respective populations with a minimum lag period.…”

“…The SDRs obtained when using methanol or formate were much lower than those with acetate and ethanol, but were slightly higher than the control (pure primary wastewater as its sole carbon source). Mokhayeri et al (2008) also found ethanol and acetate to be excellent external carbon sources to aid denitrification when comparing methanol, ethanol and acetate. They also used SBRs to acclimate biomass' to a specified substrate and then conducted a series of ex situ SDR assays.…”

“…Pure carbon sources such as ethanol (Mokhayeri et al, 2008), methanol (Foglar and Briški, 2003), acetate (Isaacs and Henze, 1995;Kampas et al, 2009;Mokhayeri et al, 2008) and VFA mixtures (Fass et al, 1994) have increased denitrification rates, but it is very important to find an economical carbon source and minimise sludge production, as the carbon source and solid waste management costs are responsible for the majority of the total costs of treated wastewater (MacDonald, 1990).…”

Sulfur-based mixotrophic denitrification corresponding to different electron donors and microbial profiling in anoxic fluidized-bed membrane bioreactors

“…This can be explained by the fact that denitrifying bacteria are more accessible to ethanol than methanol (Baytshtok et al, 2009). Some researchers also reported that ethanol fostered higher specific denitrification rates than methanol (Martin et al, 2009;Mokhayeri et al, 2008;Lu and Chandran, 2010;Salminen et al, 2014). The carbon source in a given system produces a strong impact on denitrifying performance as organic carbon and energy metabolism with diverse pathways form the foundation for heterotrophic growth.…”

Assess the Denitrification Potential of Fermented Biosolids Based on Their Specific Denitrification Rate (Sdnr)

“…These values were much higher than the 1.53-2.57 for sucrose and 1.29 ± 0.21 for wastewater that were gotten from earlier study using the same methodology [11]. The SDNR values for fermented biosolids were also comparable to the 6.1-10.0 SDNR value for methanol [2,7,10], the most studied and commonly used external carbon in US. This shows some genuine potential of fermented and dark-fermented biosolids as external carbon sources…”