The effect of Temperature on Biofilter Nitrification Performance in Recirculating Aquaculture Systems
InfoEnd date: 31 July, 2015 Project type: BSU Students' Master Thesis Project code: mge13-1K2 BSU Countries: Tanzania Lead institution: Technical University of Denmark (DTU), Denmark Project coordinator: John Peter Hewa Kinyage
Temperature is considered on the main factors affecting biofilter nitrification in recirculating aquaculture systems (RAS). Previous studies confirm the positive impact of temperature on ammonia removal while others reports nil/or negligible effects. The effects of temperature on the second step of the nitrification process, the nitrite removal is often overlooked in the current literatures. In this study, batch reactors were used to examine the acute effect of six temperatures (6, 12, 18, 24, 30 and 36 C) on moving bed biofilter (MBB) nitrification using water from a steady-state, experimental RAS (18 - 20 °C). The average surface-specific total ammonia nitrogen removal (STR) and nitrite nitrogen removal (SNR) increased with temperature between 6 – 30 °C from 0.033 to 0.25; g NH4-N m-2 day-1 and 0.033 to 0.14; g NO2-N m-2 day-1 respectively. Nitrogen removal rates were decreased at 36 °C. Long-term experiments testing the effect of temperature at 6, 18 and 30 °C showed a reduction in STR and SNR over time and reduced removal rates compared to the acute experiments. Under limited substrate concentration, 1’ order nitrification had an increase in k_1 for both ammonia and nitrite removal reaching maximum value of 0.664 and 0.229 m day-1 at 30 °C; equivalent to a 114.9% and 95.3% increase compared to the source temperature of approximately 18 °C.