MARICOPA, ARIZONA

Project Background & Challenges

In 2019, the Global Water – Palo Verde Water Reclamation Facility (WRF), located in northeastern Maricopa, AZ, was serving a growing population of 48,629 residents, while also seeing adjustments to their permit in their future. The existing treatment train, designed for 3 MGD, consisted of influent headworks (i.e. bar screen, fine screen, and grit removal), sequencing batch reactors (SBRs), EQ surge basins, cloth media disc filters, UV disinfection and an aerobic sludge digester. To accommodate the growing population and permit adjustments, a four-phase WRF upgrade with an ultimate treatment capacity of 12 MGD was proposed and agreed upon. The Arizona Department of Natural Resources had also imposed a new total nitrogen limit that required process upgrades.

The Nexom Answer

Nexom’s expertise was requested for retrofitting the existing plant with a BioPorts™ Integrated Fixed-Film Activated Sludge (IFAS) process to meet expected Total Ammonia-Nitrogen (TAN) effluent limits at the increased design flow, as well as Total Inorganic Nitrogen (TIN) objectives. Nexom’s BioPorts IFAS was designed around two treatment objectives: TAN ≤1 mg/l and TIN ≤10 mg/l.

For the Phase I upgrades, Nexom’s innovative approach allowed for the implementation of a BioPorts IFAS system that utilized existing infrastructure for pre-anoxic treatment and six new aerobic zones. The pre-anoxic and swing zones were fully integrated into the existing SBR footprint. For the new construction, fine bubble aeration was implemented in the first stage of the aerobic system for cBOD₅ removal with suspended biomass. BioPorts media was installed in the second aerobic zone with coarse bubble aeration for enhanced nitrification. The third aerobic zone had coarse bubble aeration installed for residual ammonia removal.

Upgraded System Performance

To date, Maricopa’s BioPorts IFAS maintains compliance for TAN and TIN. In 2019, the Arizona DNR added an ammonia impact ratio limit of <1 for which the plant has had zero exceedances.

The facility is also maintaining an ammonia daily maximum effluent concentration of <0.5 mg/l since the Phase 1 upgrades.

Lastly, the facility is able to maintain an effluent nitrates/nitrites concentration of less than < 8 mg/l.