Effects of Integrated Fixed Film Activated Sludge on nitrogen removal in biological nutrient removal systems

The performance of Integrated Fixed Film Activated Sludge (IFAS) was evaluated for its effect on nitrification and denitrification in a bench scale biological nutrient removal (BNR) process configured as a Virginia Initiative Project (VIP) process. The IFAS systems consisted of a sponge - like biomass support system (Captor) operated in the aerobic zone of two independent treatment trains, and a fibrous biomass support system (Ringlace) operated in the aerobic zone of one independent treatment train. A fourth treatment train containing no biomass support system was operated as a control. A range of four aerobic MCRTs was studied, from 3.4 days to 1.7 days. All experiments performed for this research effort were conducted using domestic wastewater obtained directly from Blacksburg, VA and the Virginia Tech campus.

Results indicated that the presence of the sponge - like biomass support media (Captor) freely floating in the aerobic zone mixed liquor greatly increased the ability of that system to achieve nitrification at temperatures of 12 degrees Celsius and aerobic suspended growth MCRTs as low as 1.7 days. A statistical t-test analysis demonstrated this with 99% confidence. Results early in the research, as well as previous research by Mitta (1994) indicated that fibrous biomass support systems (Ringlace) did not perform as well with respect to nitrification as did Captor, and experiments on Ringlace were discontinued midway through the research.

Increased denitrification throughout the IF AS/Captor train was noted as a result of the increased nitrification. However, the use of Ringlace appeared to enhance denitrification which occurred in the aerobic zone. Further study is recommended to verify this data. A decrease in sludge production in the IFAS train containing Captor could not be statistically established. However, observed sludge yield coefficients for the IF AS/Captor train were consistently lower than those for the Control train. A statistical analysis was not performed, but the values varied considerably so that direct comparison was difficult.