The Price is Right
Population growth and an increased demand for reclaimed water meant that the city of Scottsdale, Ariz., needed to rethink how it managed wastewater flows. Hach’s Data Delivery Services (DDS) gave the city unprecedented access to the flow data that is essential for billing and management.
The city of Scottsdale has seen considerable population growth since its incorporation in 1951—from 2,000 to a population today in excess of 240,000 people. As the population grew and water resources declined, the city took steps in the 1990s to implement a water reuse plan to meet this growth.
Water Operations in Scottsdale
Rather than discharging wastewater to a regional system, known as the sub-regional operating group (SROG), the city constructed its own water reclamation plant in 1998, and it included advanced wastewater treatment. Final effluent from this facility, known as the Water Campus, could be used to provide turf irrigation water to 23 northern Scottsdale golf courses or for groundwater recharge. Most of the wastewater treated at the Water Campus is pumped from five large lift stations. Water that is used for recharge undergoes additional treatment that includes reverse osmosis and microfiltration to assure the highest quality of water prior to it being recharged.
Scottsdale’s water resources department (WRD) is responsible for the operation and maintenance of the city’s water and wastewater systems. Besides a sewer collection system that involves 1,400 miles of sewers and 43 wastewater lift stations over a 185-sq-mile area, there are two water reclamation plants within the city. The remainder of the wastewater flow is discharged by gravity into the SROG system. The collection system is divided into five sewer sub-basins, each of which is a distinct wastewater collection system with its own characteristics.
Created in 1979, SROG provides wastewater treatment at the 91st Avenue Wastewater Treatment Plant for the cities of Phoenix, Glendale, Mesa, Tempe and Scottsdale. A portion of the effluent from the 91st Avenue treatment plant is used for cooling water at a nuclear power plant. Because of the contractual arrangement of this effluent, each SROG city must maintain a certain flow to the 91st Avenue treatment plant. Two meters located at Scottsdale’s meter station act prior to the flow entering the SROG system.
“The flow commitment into the SROG system and the increased demand for reclaimed water presented an opportunity to better manage our wastewater flows,” said Richard Sacks, P.E., senior water resource engineer for Scottsdale.
The Need for Meters
While the wastewater lift station discharges were metered, there were no meters to determine the gravity flow characteristics. This led the WRD on a search for flowmeters that would provide the needed data.
“What we are trying to do is get a handle on our flows from the sub-basins and verification of the billing meters at the meter station into the SROG system,” Sacks said.
Sacks was familiar with the city of Phoenix’s use of the Marsh-McBirney Flo-Dar flowmeters in similar temporary/permanent monitoring applications and in regional system interceptors. In 2008, Sacks visited the Water Environment Federation Technical Exhibition and Conference in Chicago and viewed an in-booth demo on Hach’s DDS. After discussing his application specifics, including the use of the meters in deep manholes and any effects of hydrogen sulfide on the meters, personnel recommended DDS as an ideal solution.
Establishing a Flow History
With DDS, users never have to visit flow monitoring sites again, which keeps flow monitoring personnel safe. Hach DDS-certified personnel install award-winning, Web-enabled flowmeters and handle any maintenance for a low monthly fee. No flowmeter purchase is required, and unedited flow data is available 24/7 via any Web browser.
After further exploration of DDS with his local rep, Ted Cameron with The Cameron Group, and Andrew Gilmore of Carollo Engineers, an 18-month DDS contract was signed. The feature that sealed the deal, according to Sacks, was the Web-based concept that allowed him to get flow data anytime, any place.
In February 2009, six meters were installed at strategic locations throughout the community in line sizes from 24 to 42 in.
Regarding the city’s decision to utilize DDS, Sacks said: “It really fulfills our needs. With the meters, we can actually determine where the water is coming from ... I’ve got to tell you, the price was right too.”
Sacks views flow data from the DDS meters on a daily basis. “It’s interesting because I can really pick up the issues,” he said. “I can get a chart that shows maximum, average and minimum flow and graphically show the results. I can do that at home or do it here.”
Prior to the DDS meter installations, Sacks was unaware that surcharge conditions were happening at some of the sites during certain times of the day. “Now we have the data even under surcharge conditions,” he said.
Sacks also developed a spreadsheet that takes data from both the Flo-Dar meters and the meters on the discharge. “Between the Flo-Dar meters and the discharge meters, I have a real good handle on our flows,” he said. “We now know what we have coming into the station and we know what goes out. And then there’s an overflow which goes into the regional system. It’s a quick and dirty approach to permanent monitoring. We may expand the number of sites, but for now the six are giving us good data.”
As the DDS meters continue to create an accurate and reliable flow history that will allow the city of Scottsdale to maximize the use of its treatment system, a determination will be made on whether to keep the meters at their current location or to relocate them. Future plans call for permanent flow monitoring throughout the entire system.