Energy efficiency approaches in water resource recovery facilities (WRRFs) can be divided into two broad categories: 1) high-efficiency equipment and energy recovery systems that reduce purchased energy use under virtually all operating conditions, and 2) systems that modulate equipment output in response to daily and diurnal variations in plant load conditions. This project investigated the effectiveness of real-world wastewater equipment and control systems in responding to increases and decreases in influent flows, organic loads, and nutrient loads. The analysis was based on a statistical review of daily operating data and electrical data, with a focus on the correlations between blower power consumption and changes in plant influent loads.
This analysis can be used to gauge the effectiveness of automated aeration control systems. There is considerable variation in the industry in the configuration and complexity of these control systems, ranging from manual blower adjustments to sophisticated multi-level dissolved oxygen (DO) and ammonia (NH3)-based aeration control systems. Variability metrics were also used to help identify plants where barriers to effective equipment modulation exist. The statistical analysis found that energy use, including blower energy consumption, is relatively insensitive to changes in plant loading. Blower energy use in plants that nitrify is correlated primarily with process parameters related to NH3 removal, although the blower energy response is only 20-30% of the stoichiometric load increase.
The submetering data gathered for this project were also used to compare the energy intensity of diverse secondary treatment configurations, disinfection technologies, and solids treatment approaches.
This project was managed by the Water Environment & Reuse Foundation. The Water Research Foundation was a co-funder of this project. Published in 2017.