Preserving Paradise: How a Utility in Key West is Maximizing Water Reuse

Key West is one of America’s most scenic locales. Situated in the Florida Keys southwest of Miami, it is visited by millions of people each year and is home to more than 30,000 year-round residents. While there’s plenty of ocean, potable water is a precious commodity that is piped 125 miles from the mainland. Restrictions aren’t uncommon during drought season. So every drop counts, and reuse is a key part of the island’s conservation strategy.  

Challenge

Such water scarcity poses unique challenges to KW Resort Utilities Corp. (KWRU) the utility firm that provides wastewater management, wastewater recovery, and wastewater treatment in the region. KWRU began operation in the late 1960’s and has worked hard over the decades to keep up with wastewater needs as population and tourism have boomed, spurred by land reclamation and development.

Solution

In 1983, KWRU began a relationship with Evoqua Water Technologies, which provided a 250,000-gallon-per-day (GPD) DAVCO™ field-erected extended aeration treatment plant. Evoqua was chosen because their field-erected tanks can be set up quickly and adapted easily to meet changing needs — a good fit with KWRU’s step-by-step strategy for managing growth. “The advantage is that you’re able to incrementally increase the size of your plant with the growth of your community,” says KWRU president Chris Johnson, “and still you’re able to maintain an operational environment that’s familiar and uniform.”

In 1995, outgrowing the capacity of the initial plant, KWRU added an identical Davco field-erected treatment plant. By the late 2000s, the utility was not only outgrowing capacity again, but also facing a new challenge: tighter treatment limits of 5 ppm suspended solids, 5 ppm BOD, 3 ppm nitrogen, and 1 ppm phosphorous. To meet this challenge, KWRU added a 56,000 GPD standalone clarifier in 2007 which facilitated the conversion of the entire plant operation to a three-stage Biological Nutrient Removal (BNR) process.

The overhaul was completed ahead of the adoption of the new standard. By the middle of the 2010s, however, the facility once again needed more capacity. “We were starting to exceed 90% of capacity,” says Johnson. To address this issue, KWRU expanded the treatment capacity of the existing Davco Field-Erected Biological Treatment system to 849,000 GPD by adding a new three-stage 350,000 GPD plant to augment the existing plant capacity of 499,000 GPD.

Key West Resort Utilities selected Evoqua Water Technologies and sales partner Heyward Florida Incorporated for this turnkey project. The three-stage BNR activated sludge plant includes steel outer walls 90 feet in diameter and 20.5 feet high. Evoqua supplied steel tanks, walls for the wastewater plant, field erection, field painting and commissioning labor.

“We’re thinking about our future in this densely populated, fragile marine environment,” says Chris Johnson. “Evoqua has helped us make great progress in addressing our community’s needs over the last 20 years, and we expect this project to help us to continue to meet those needs for 20 more.”