Reaction Kinetics of Municipal Wastewater Treatment with Temperature Effects

Anaerobic microorganisms have ideal growth kinetics at temperatures greater than 25 degrees Celsius; however, wastewater treated at the Laramie Wastewater Treatment Plant experiences temperatures ranging from 10 to 25 degrees Celsius. Due to temperature fluctuations in the wastewater, evaluation of growth kinetics of the microorganisms in the system is required. At low temperatures, the microorganisms degrade constituents slowly, so organism retention times in the reactor will have to be adjusted to produce the desired treatment levels. Using microbial reaction kinetics, the required organism retention time was determined to be 186 days at temperatures of 10 degrees, whereas at temperatures of 25 degrees, retention times can be lowered to 31 days. Organism retention times can be set by changing the solids removal rate of the organisms from the bioreactor. At organism retention times ranging from 31 to 186 days, the organism concentrations in the reactor will be between 1981 to 2380 mg/L. These organism concentrations and retention times were then used by the rest of the design team to determine membrane area for the anaerobic membrane bioreactor, as well as biogas production estimates.