Assessment of the endogenous respiration rate and the observed biomass yield for methanol-fed denitrifying bacteria under anoxic and aerobic conditions.

Water science and technology : a journal of the International Association on Water Pollution Research

PubMedID: 28067645

Alikhani J, Al-Omari A, De Clippeleir H, Murthy S, Takacs I, Massoudieh A. Assessment of the endogenous respiration rate and the observed biomass yield for methanol-fed denitrifying bacteria under anoxic and aerobic conditions. Water Sci Technol. 2017;75(1):48-56.
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(-1) for endogenous respiration rate under aerobic conditions at 20 °C, 0. 102 ± 0. 013 day(-1) under anoxic conditions at 20 °C, and 0. 214 ± 0. 044 day(-1) under 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.