Transient temperature effects on biofilters in recirculating systems ammonia removal rates

Abstract

Acclimation of biological filters and ammonia oxidation at transient temperature regimes was the focus of the research. A batch system of automated temperature controlled tanks was used to determine effects of temperature on biofilter response to total ammonia nitrogen utilization. Each tank contained internal biofilters loaded with synthetic chemical feedstock. The biofilters were exposed to temperature regimes of 13 °C, 20 °C and 30 °C steady state temperatures in the first experiment, and cyclical (diurnal) temperatures of 20 ± 3 °C and 30 ± 3 °C in the second experiment. A direct linear regression line method was used, with tau (τ) value from the slope of the linear regression line used to determine the biofilter substrate utilization response to varying temperature regimes.Biofilter response was determined as the capability to utilize total ammonia nitrogen (TAN) by ammonia oxidizing bacteria (AOB). Tau (τ) values for ammonia oxidation were 40.73 day−1, 58.81 day−1 and 159.70 day−1 at 13 °C, 20 °C and 30 °C respectively. Total ammonia nitrogen substrate utilization rates as indicated in a decay plot differed significantly (P < 0.05) between temperature regimes 20 and 30 °C. However substrate utilization between 13 and 20 °C were not different (P > 0.05). Ammonia oxidation tau values were 118.20 day−1 and 223.50 day−1 at (20 ± 3 °C) and (30 ± 3 °C) diurnal temperatures respectively. These were significantly different (P < 0.05). The data in this study can be applied to future seeded or acclimating biofilters operating within these temperature ranges.