Balancing yield, kinetics and cost for three external carbon sources used for suspended growth post-denitrification

Abstract

Facilities across North America are designing plants to meet stringent limit of technology (LOT) treatment for nitrogen removal. In the Mid-Atlantic region of the United States, this is in response to the Chesapeake Bay Agreement, which limit effluent total nitrogen discharges from wastewater treatment plants to between 3-5 mg/L. Since denitrification is crucial for the removal of nitrogen, maximizing this process step will result in a decrease in nutrient load to the receiving waters. Of particular interest is the use of an alternate external carbon source to replace the most commonly used carbon, methanol. Three external carbon sources were evaluated in this study including: methanol, ethanol and acetate at 13 degrees C. The aim of this study was to evaluate the relative benefits and constraints for using these three carbon types. Laboratory scale Sequencing Batch Reactors (SBRs) were set up to grow and acclimate carbon free biomass to the specified substrate while in-situ Specific Denitrification Rates (SDNRs) were conducted concurrently. The results suggest that the SDNRs for acetate (31.0 + or - 4.6 mgNO(3)-N/gVSS/hr) and ethanol (29.6 + or - 5.6 mgNO(3)-N/gVSS/hr) are higher than that for methanol (10.1 + or - 2.5 mgNO(3)-N/gVSS/hr). The yield coefficients in g COD/g COD were observed to follow a similar trend with values of 0.45 + or - 0.05 for methanol, 0.53 + or - 0.06 for ethanol and 0.66 + or - 0.06 for acetate.

Proteomics unravels metabolic strategies employed by nitrate reducing bacteria during growth on different carbon sources

“…Similarly, higher yield coefficients for denitrifying bacteria grown on ethanol than methanol has been previously observed using activated sludge (Mokhayeri et al 2009;Peng et al 2007). The kinetics during three phases demonstrated the versatility of M. universalis FAM5 in responding to differences in the carbon substrate in terms of denitrification kinetics (Figure 2), which was manifested in sustained nitrate conversion during all three phases (Figure 1).…”

Enhancing combined biological nitrogen and phosphorus removal from wastewater by applying mechanically disintegrated excess sludge

“…A simple method to improve the effectiveness of nutrient removal is to add commercially available organic compounds (i.e. methanol, ethanol, acetic acid), called "conventional" carbon sources (Cho et al, 2004;Mokhayeri et al, 2009). Because these processes generate additional operational costs, alternative solutions to the problem are currently being sought.…”

Endogenous Nitrous Oxide Emission for Denitrifiers Acclimated with Different Organic Carbons

“…The anaerobic, anoxic and aerobic (A 2 O) process has been widely used for biological nitrogen and phosphorus removal from wastewater. Shortages of organic carbon in influent wastewater also occurs, and the supplement of external organic carbons such as acetate and methanol has been examined and practiced for enhancing biological nitrogen removal [5,6]. Another enhanced biological nitrogen removal is through endogenous denitrification in intermittently aerated systems or in processes with alternative anoxic/oxic phases [7,8].…”