A Pilot Scale Study of Low Dissolved Oxygen Nutrient Removal Supplemented with Ammonia-Based Aeration Controls
Abstract
In order to refine a previously acclimated pilot to low dissolved oxygen (DO) conditions for
nutrient removal, ammonia-based aeration control was introduced in an effort to successfully
remove ammonia throughout an entire year. Historical operations of the low DO pilot, operated at
a fixed DO setpoint of 0.5 mg/L, allowed for efficient nutrient removal until water temperatures
decreased with drastic seasonal changes present in at the Nine Springs Wastewater Treatment Plant
in Madison, WI. By implementing ammonia-based aeration controls in the secondary treatment
process, triggered by operator adjustable ammonia setpoints, the pilot was allowed to operate
between high and low DO modes to call for additional oxygen when ammonia loads increased,
and call for less oxygen, as an energy saver, when an ammonia setpoint is achieved. In addition,
data from the ammonia probe was compiled and summarized which provides an enhanced
understanding of the process that was previously not possible to obtain. This shows the daily, and
even hourly, variability that the pilot experiences in response to influent loadings and seasonal
transitions. In comparing the first iteration of ammonia-based controls with the previous years of
fixed DO operation, recommendations and enhancements are provided to optimize the process for
future work. The study provided insight into the various physical configurations to be considered
with the control strategy and also evaluates the side effects, both positive and negative, that come
with implementing ammonia-based controls on a low DO pilot reactor.
Subject
dissolved oxygen
nutrient removal
wastewater