title: Assessment of the endogenous respiration rate and the observed biomass yield for methanol-fed denitrifying bacteria under anoxic and aerobic conditions.
abstract: In this study, the endogenous respiration rate and the observed biomass yield of denitrifying methylotrophic biomass were estimated through measuring changes in denitrification rates (DNR) as a result of maintaining the biomass under methanol deprived conditions. For this purpose, activated sludge biomass from a full-scale wastewater treatment plant was kept in 10-L batch reactors for 8 days under fully aerobic and anoxic conditions at 20 °C without methanol addition. To investigate temperature effects, another biomass sample was placed under starvation conditions over a period of 10 days under aerobic conditions at 25 °C. A series of secondary batch tests were conducted to measure DNR and observed biomass yields. The decline in DNR over the starvation period was used as a surrogate to biomass decay rate in order to infer the endogenous respiration rates of the methylotrophs. The regression analysis on the declining DNR data shows 95% confidence intervals of 0.130 ± 0.017 day-1for endogenous respiration rate under aerobic conditions at 20 °C, 0.102 ± 0.013 day-1under anoxic conditions at 20 °C, and 0.214 ± 0.044 day-1under aerobic conditions at 25 °C. Results indicated that the endogenous respiration rate of methylotrophs is 20% slower under anoxic conditions than under aerobic conditions, and there is a significant temperature dependency, with an Arrhenius coefficient of 1.10. The observed biomass yield value showed an increasing trend from approximately 0.2 to 0.6 when the starvation time increased from 0 to 10 days.
authors.affiliation: Civil Engineering Department, The Catholic University of America, Washington, DC 20064, USA E-mail: massoudieh@cua.edu.
authors.forename: Jamal
authors.initials: J
authors.lastname: Alikhani
authors.affiliation: DC Water, Washington, DC 20032, USA.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Al-Omari
authors.affiliation: DC Water, Washington, DC 20032, USA.
authors.forename: Haydee
authors.initials: H
authors.lastname: De Clippeleir
authors.affiliation: DC Water, Washington, DC 20032, USA.
authors.forename: Sudhir
authors.initials: S
authors.lastname: Murthy
authors.affiliation: Dynamita, 26110, Nyons, France.
authors.forename: Imre
authors.initials: I
authors.lastname: Takacs
authors.affiliation: Civil Engineering Department, The Catholic University of America, Washington, DC 20064, USA E-mail: massoudieh@cua.edu.
authors.forename: Arash
authors.initials: A
authors.lastname: Massoudieh
mesh_terms: D000332:Aerobiosis; D000693:Anaerobiosis; D001419:Bacteria / Q000145:classification / Q000378:metabolism*; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology*; D058440:Denitrification; D000432:Methanol / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology*; D056152:Respiratory Rate; D012722:Sewage / Q000382:microbiology; D062065:Wastewater
chemical_list: D000432:Methanol; D012722:Sewage; D062065:Wastewater