The Wickenburg South Wastewater Treatment Plant (SWWTP) is an 800,000 gal per day wastewater treatment plant (WWTP), serving the majority of 7,400 citizens of Wickenburg, Ariz. The current SWWTP was initially introduced in 2003 with minor and single component upgrades between 2007 and 2012. The original 2003 infrastructure had remained in service and experienced major degradation and loss of full service and redundancy.
At the time, the town had begun actively managing and prioritizing how to improve and upgrade the facility to meet the town goals of sustainable compliance, available capital budget, desired schedule, resilient performance, redundancy and reduction in long-term operations, and maintenance costs.
The result of efforts by the town and GHD to evaluate projects identified the upgrade of the primary aeration basins as a top priority. The existing aeration basins consisted of two 330,000 gal basins with draft tubes and surface mechanical aerators. Besides experiencing advanced degradation, this system was found to struggle to sustain the desired dissolved oxygen (DO) concentrations and to properly monitor the DO for process control.
Other aspects of the project included upgrading to turbo blowers with fine bubble air diffusion and advanced control and to add a redundant pump for recycled activated sludge (RAS) return line to the anoxic basin.
The entire SWWTP influent had to be bypassed around the first aeration basin during the highest flows of the year. The addition of the additional RAS pump to one of the aeration basins, which was not installed at the time of the initial construction, also was a challenge. The new redundant RAS pump was to be connected to the existing large diameter return line that feeds the anoxic basin.
The significant cost savings in this projection was the reduction in long-term energy use. Removing the mechanical surface aerator, and replacing it with high-efficiency, turbo blowers and fine bubble diffused air, provided more than an 80% reduction in horsepower to operate the aeration process. Each blower is sized for the maximum daily demand for the rating of the facility.
Additionally, GHD paid special attention to providing the ability to expand the facility in the future by providing the space and connections for a future third blower. This will allow the facility to expand the primary aeration processes, in the same basins, with the same level of redundancy.