Potable Reuse Project Case Studies
Editor’s note: This article first appeared in the July/August 2015 issue of Water Efficiency.
The First in New Mexico
Cloudcroft, NM, is a 110-year-old mountain resort community in the southeast corner of New Mexico about 200 miles from Albuquerque and 90 miles from El Paso. It normally has 850 residents that grow to 2,000 during holidays, says Scott Powell, the water and wastewater plant’s operator.
Powell explains the village has limited rainfall with a lot of fluctuations. The National Guard had to bring in water in the early 2000s, which precipitated their interest in potable reuse, says Eddie Livingston, the project principal with Livingston Consultants and consulting engineer for Cloudcroft.
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Planning for direct potable reuse began immediately, says Powell, and initial construction began in 2005, but issues with contracting stalled the project by 2007. Now back on track, construction bids were released in June to build the membrane bioreactor (MBR) and upgrade the existing wastewater treatment plant. Construction on a new treatment plant will begin in 2016 and take about two years to complete, according to Livingston.
Livingston says currently the 1970s era wastewater treatment facility uses a trickling filter process before the wastewater is discharged down the local dry canyon riverbed.
Livingston described what the new wastewater reclamation facility will do. As wastewater flows from the current wastewater treatment plant, it will go through the MBR and be disinfected with chloramines. It will be stored, then 100,000 gallons will be sent through reverse osmosis (RO) and advanced oxidation, including ultraviolet disinfection combined with hydrogen peroxide.
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The treated water will first be stored in a one-million gallon reservoir, then 80,000 gallons will be blended with 80,000 gallons of groundwater and again treated with ultrafiltration, UV disinfection, and then granular activated carbon (GAC). Finally, it will be chlorinated and pumped into the distribution system, says Livingston.
Xylem is supplying the RO and ultrafiltration technologies and Trojan is providing the UV and disinfection technology.
After blending with the groundwater supply, 160,000 gallons/day (gd) will be available for distribution, says Livingston. On average, village water usage is between 160,000 and 180,000 mgd. The remaining 20,000 gallons of reclaimed wastewater not blended will be used for forest firefighting,construction, and road maintenance, says Livingston.
Cloudcroft’s direct potable reuse project will be the first in New Mexico and second in the US, says Livingston. The New Mexico Environment Department is now formulating guidelines and has highlighted the project on its website as a model for other communities.
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Says Livingston, “Once this project starts to supply Cloudcroft, it secures a water supply for its citizens and serves as a model. It demonstrates that wastewater is a resource, and is a great example of how to take advantage of the resource.”
Constructed Wetlands Cleanse Water
Clayton County, GA, is prone to drought, says Chris Hamilton, Water Reclamation Manager for the Clayton County Water Authority, which has operated an indirect potable reuse facility since 2004. The county is divided by the subcontinental divide and lies in the upper part of the Flint River Basin which flows to the Gulf of Mexico and the Ocmulgee River Basin which flows to the Atlantic Ocean. The county has no large rivers or impoundments to draw water from. The groundwater quantity and quality is highly variable because of the predominance of dense bedrock that holds very little water. The county is also highly populated, being home to approximately 270,000 residents.
The Clayton County Water Authority had been spraying its treated wastewater on land, called a land application system, since the 1970s and operated the system for almost 30 years. But it was reaching the end of its life cycle, says Hamilton.
During the development of CCWA’s 2000 Master Plan, “we decided reclamation and constructed wetlands was the better solution,” says Hamilton. It requires much less land, energy, and maintenance than the land application system, he explains.
With the help of CH2M HILL, its selected design firm, the Authority upgraded two of its three wastewater treatment plants in 2002 to advanced treatment standards and to transform the land application system into constructed wetlands requiring only 15 acres to treat one million gallons of treated plant effluent.
Constructed wetlands treatment is a natural process involving plants, soils, and bacteria that naturally occur within the aquatic ecosystem and all play a part in removing residual nutrients. Wetland plants were selected based on the ability to prosper in the local climate. After the wastewater is treated at the Water Reclamation Facility, the reclaimed water is pumped about five miles to the wetlands where it remains for five days before flowing into the Shamrock and Blalock reservoirs.
“The constructed wetlands gave us the opportunity to keep water in the watershed and shield ourselves in droughts,” says Hamilton. During Georgia’s second worst drought in 2007, three years after the water reuse system began operating, Clayton County’s raw water reserves remained at 77% of capacity. According to Hamilton, the new water reclamation system drew a lot of industry attention.
Energy savings was an additional benefit. Electricity use was reduced by 5.3 GWh annually after moving from land application to water reclamation.
The W. B. Casey Water Reclamation Facility is the largest of CCWF’s water reclamation facilities and has a capacity of 24 mgd of treated effluent that is eventually sent to the E. L. Huie constructed wetlands. This water is constantly being tested and monitored. Hamilton says the reclaimed water is piped from the wetlands to an area where it flows over rocks that provide aeration before flowing naturally into the raw water reservoirs from which the drinking water is drawn and destined for the water treatment plant, which prepares it for distribution to residents.
Originally built in 1958, the W. B. Casey facility has been expanded and upgraded several times over the years. The most recent upgrade came online July 1, 2004. It uses chemical, biological, and mechanical methods to clean the wastewater, says Hamilton.