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Sub-Regional Operating Group (SROG)

Created in 1979, the Sub-Regional Operating Group (SROG) is the result of an agreement (SROG Agreement) between the cities of Glendale, Mesa, Phoenix, Scottsdale, and Tempe pertaining to liability ownership and operation of the 91st Avenue Wastewater Treatment Plant (WWTP). Multi-city coordination for purposes of encouraging compliance with federal requirements and consistency of implementation is accomplished through monthly multi-city meetings attended by representatives from each Program, as well as through periodic meetings with individual Programs.

The original 91st Avenue WWTP, a five mgd cooperative venture between Glendale and Phoenix, was built in 1958. This plant was later replaced with a 45 mgd plant that was subsequently expanded throughout the years. The capacity of the 91st Avenue WWTP is now 179 mgd.

Each SROG city implements an appropriate Industrial Pretreatment Programs within their own jurisdiction. The City of Phoenix continues to provide counsel, guidance and assistance to the Pretreatment Programs in the metropolitan area. Multi-city coordination for purposes of encouraging compliance with federal requirements and consistency of implementation is achieved through both monthly multi-city meetings attended by representatives from each SROG city and other local jurisdictions, and through periodic meetings with individual Program staff.

The SROG cities jointly participate in many projects. Examples of these include:

• Salinity Study – The salinity study is evaluating salinity sources in both the raw water supply and the wastewater. Contributors to Total Dissolved Solids (TDS) in municipal wastewater include background levels from source waters, residuals from water reclamation plants, industrial wastewater, residential water softeners, and domestic activities. TDS is being evaluated to determine the impact on both the water treatment system as well as the re-use system. Additional projects related to TDS include membrane technologies and brine research.
• Local limits –Local limits are a uniform set of Phoenix valley-wide wastewater pretreatment limits, based upon local site-specific Wastewater Treatment Plant (WWTP) and environmental considerations. These limits are reevaluated every 5 years.
• Metering Station Projects – The SROG metering stations are used determine the flows and loadings from each of the SROG cities to the 91st Avenue WWTP. These flows and loadings are used for future planning projections and for billing purposes. Some of the metering station projects currently underway are a state of the art metering station design, station electronics upgrades, and yearly calibration events.
• BMPs Considered – Members of the Pollution Control Division Administration Section are active participants in the SROG Technical Advisory Committee (TAC). SROG TAC is currently working on a project to evaluate Fluoride, Molybdenum, Selenium and DEHP  Best Management Practices (BMPs.)