Using off-gas testing to map mixing gradients and audit blower capacity.

A water resource recovery facility sited in a region at a high elevation has experienced the effects of over-designing its blowers. In this case study, we used off-gas analysis and site-specific power tariffs to quantify actual process loading and air requirements, and we quantitatively evaluated various options for blower replacement or upgrade. Off-gas analysis mapped the oxygen uptake rate at the surface of the tank, suggesting that the tanks were not evenly loaded across their sections.