Examining the influence of substrates and temperature on maximum specific growth rate of denitrifiers

Abstract

Facilities across North America are designing plants to meet stringent limits of technology (LOT) treatment for nitrogen removal (3-5 mg/L total effluent nitrogen). The anoxic capacity requirements for meeting LOT treatment are dependent on the growth rates of the denitrifying organisms. The Blue Plains Advanced Wastewater Treatment Plant (AWTP) is one of many facilities in the Chesapeake Bay region that is evaluating its ability to meet LOT treatment capability. The plant uses methanol as an external carbon source in a post-denitrification process. The process is very sensitive to denitrification in the winter. One approach to improve anoxic capacity utilization is to use an alternative substrate for denitrification in the winter to promote the growth of organisms that denitrify at higher rates. The aim of this study was to evaluate denitrification maximum specific growth rates for three substrates, acetate, corn syrup and methanol, at two temperatures (13 degrees C and 19 degrees C). These temperatures approximately reflect the minimum monthly and average annual wastewater temperature at the Blue Plains AWTP. The results suggest that the maximum specific growth rate (mu(max)) for corn syrup (1.3 d(-1)) and acetate (1.2 d(-1)) are higher than that for methanol (0.5d(-1)) at low temperature of 13 degrees C. A similar trend was observed at 19 degrees C.

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

“…Acetate can be readily used by other biomasses, but the acetate biomass does not seem to readily use either methanol or ethanol (at least after 24 hours acclimation).CONCLUSIONS † At 138C, the SDNR for methanol grown biomass was found to be approximately 9.2 mg NO 3 -N/g VSS/hr, the SDNR for ethanol grown biomass was about 30.4 mg NO 3 -N/g VSS/hr and the SDNR for acetate utilisers was about 31.7 mg NO 3 -N/g VSS/hr. The denitrification rate with acetate was approximately three times that of methanol confirming other work byMokhayeri et al (2006). † The final (at the end of 24 hour-acclimation) ex situ SDNR value of acetate with ethanol grown biomass was approximately 25.6 mg NO 3 -N/g VSS/hr, and ethanol and acetate with methanol grown biomass was 9.7 and 7.3 mg NO 3 -N/g VSS/hr, indicating near complete acclimation of these substrate-biomass combinations toTable 1 | Comparison of ex situ SDNR rates for the different substrates added to each of the grown biomass during 24 hours SDNR (mg NO 3 -N/g VSS/hr) that of the original substrate-biomass.…”

“…However, it has been observed that the denitrification process at Blue Plains AWTP is retarded in the winter due to an expected decline in microbial growth rates at lower temperatures. Results from the study conducted at Blue Plains AWTP suggest that the mmax for methanol utilisers at 198C is double the mmax obtained at 138C and denitrification with methanol addition does not achieve low total nitrogen values during the winter (Mokhayeri et al 2006). Minimum winter wastewater temperature at Blue Plains AWTP is approximately 138C.…”

Estimating The Kinetics And Stoichiometry Of Heterotrophic Denitrifying Bacteria With Glycerol As An External Carbon Source

“…The maximum specific growth rate using glycerol as the substrate is approximately 2.5 times greater than the μ MAX value of 1.3 d -1 at 20ºC reported by Dold et al (2008) and Nichols et al (2007) using methanol as an external carbon source and similar to the μ MAX values of 3.7 d -1 at 19 ºC for acetate (Mokhayeri et al, 2006). Likely, the μ MAX for glycerol is similar to the μ MAX of acetate.…”

“…274 heterotrophic bacteria participating in the process (Grabinska-Loniewska et al, 1985;Dold et al, 2008). Methanol is the most widely used external carbon source for denitrification since it is low in cost (Mokhayeri et al 2006). However, the need to evaluate alternate sources of external carbon has been recognized.…”

Phycoremediation strategies for rapid tertiary nutrient removal in a waste stream

“…Although algal C:N requirements (average of 6.6) are similar to, if not greater than those of denitrifiers (which ranges between 2 and 10), denitrifiers are heterotrophs and so require an organic C source and electron donor to fuel denitrification. Methanol, the most common C compound added to fuel bacteriallymediated denitrification in WRRFs, has many drawbacks including its cost, safety, and reliability [26,49]. By using algae to mediate nutrient removal in bioreactors, the need for organic C additions is removed thereby providing a significant cost savings.…”