Show Low Wastewater Treatment Plant Evaluation and Expansion

Show Low, AZ


2.5 MGD WWTP Expansion

The City of Show Low commissioned PACE to develop an improvement plan and perform design services to upgrade its aerated lagoon WWTP with a design treatment capacity of 2.46 MGD. The existing WWTP process needed to have the capabilities to meet stringent effluent requirements, especially for ammonia. In addition, future, more stringent effluent requirements require significant improvements to the existing WWTP. A previous engineering report recommended constructing a 1.75 MGD mechanical wastewater treatment facility on the existing lagoon site to meet the flow projection of 1.72 MGD required for the next 20 years. PACE was asked to perform an evaluation using capital construction costs, operation and maintenance costs, and 20-year life cycle analyses to confirm the recommendation. Recognizing that the facility already had lagoon basins, PACE recommended the design and construction of a two-basin 2.5 MGD Extended Aeration Activated Sludge (EAAS) facility utilizing the footprint of one of the aerated lagoons. This provided the future capacity and full process redundancy for the current flow up to 1.5 MGD while minimizing earthwork construction costs. In addition, the remaining aerated lagoon served as emergency storage for process by-pass and high wet weather flow. The new 2.5 MGD WWTP utilizes an EAAS process based on Parkson’s Biolac® process to produce effluent quality that can meet AZ Title 18 BADCT effluent limits for Total Nitrogen (TN) of <10 mg/ L. The construction of the facility was completed in early Spring of 2016, and the facility has consistently produced effluent with TN level of less than 3 mg/L (and at times <1 mg/L). The WWTP Upgrade Project was completed on schedule and at a budget of less than $4 per gallon.


Water System SCADA and Controls Integration

After evaluating the City’s existing water production, storage, and distribution Supervisory Control and Data Acquisition (SCADA) system, the City hired PACE to provide engineering services to design and commission the recommended SCADA improvements for the Water facilities. PACE’s Instrumentation and Controls Group provided PLC Upgrades at the existing groundwater well sites by replacing the outdated PLC controllers with new PLC platforms to control the wells based on well level, maintained flow rate, or constant pressure. Upgrades included the replacement of PLC’s and HMI touch interface screens at well sites, tank sites, and booster stations and the installation of a radio network using high-speed Ethernet radios between the SCADA office and each of the well and tank sites for the water system. In conjunction with the high-speed Ethernet radios, PACE configured and installed an advanced cellular platform for well sites buried in no signal zones to complete the entire network. With the ability to communicate to each well site with advanced speed, PACE installed and programmed a new SCADA platform to control, adjust setpoints, monitor, collect data, and generate valuable reports on flows and totals from each client’s well sites and booster stations. The client is now able to monitor and control each well site remotely using this new SCADA platform, giving them the ability to quickly respond to an emergency situation and interact with other operators to collaborate on alarm conditions in tangent through their mobile phone device using the interactive Win911 alarm Mobile Application.


PACE’s ability to provide both process design and engineering, along with the ability to provide controls integration has made the Show Low Water and WWTP Projects a great success for the community.


Key Features:

  • Facility evaluation and improvement planning with prioritization of improvements
  • Value engineering / performance specifications
  • Treatment process conversion from aerated lagoon to 2.5 MGD Biolac EAAS
  • Alternative design approach met high effluent quality requirements while providing redundancy and emergency storage
  • Final WWTP total cost of less than $4/ gallon
  • Performed instrumentation and controls programming and integration services
  • Project was within 10% of Engineer’s Cost Estimate
  • PLC Upgrades at the existing well sites
  • Radio network using high-speed Ethernet radios
  • Advanced cellular platform
  • Installed and programed new SCADA platform

City of Show Low

Communications, Instrumentation & Controls, PLC, SCADA, Wastewater Treatment