About the author: Elizabeth Lisican is associate editor for Water & Wastes Digest. Lisican can be reached at 847.954.7958 or by e-mail at [email protected].
Related search terms from www.waterinfolink.com: reclaimed water, ASR well, biosolids
Even though the Englewood Water District (EWD) is set in a beach community on the Gulf of Mexico, its pioneering vision never seems to take a vacation: Its water reclamation facility (WRF) recently earned praise for its reclaimed water system—especially around its milestone as the first Florida utility to develop and fully permit a reclaimed water aquifer storage and recovery (ASR) system to help manage seasonal imbalances in reclaimed water supply and demand.
The ASR project garnered two recent awards: the David W. York Award, offered by the Florida Water and Environment Assn. and recognizing outstanding reclaimed water quality, innovative uses of reclaimed water and the reclaimed water system, as well as the Small Project of the Year Award from the WateReuse Assn., recognizing its public access reuse system, which serves recreational, commercial, residential and industrial users throughout its service area.
EWD has approximately 17,000 water customers and 13,800 sewer connections. The district serves a population of approximately 42,000 people, and therefore provides sewer to proportionally less, or 34,000, people.
ASR at EWD: A Decade in the Making
In 2000, four years after the WRF was built, EWD decided to increase the facility’s storage capacity. In Florida, there is often an imbalance between when utilities need water and when water is available (i.e., anywhere from two to three times the amount of reclaimed water is used during the dry season than during the typical wet-weather period).
EWD worked with engineering consultant Mark McNeal of ASRus on the ASR well, and testing on it began in 2001. The technology cost $1 million, with one-half funded by the Southwest Florida Water Management District and the other by EWD.
“The first step on all these projects is to go through a feasibility study and look at their needs; we always look at their reclaimed water supplies and their reclaimed water demands,” McNeal said. “So, we look at that and we determine the amount of storage that they really need to get through a dry season—how much more water will they really need? And through that analysis we then look and see: Does ASR make sense?”
The ASR well stores reclaimed water that is not being used by customers in a very salty 20,000-total dissolved solids aquifer. The reclaimed water has a lower density, or salt level, than the water in the aquifer. This creates a freshwater storage bubble in the aquifer, which allows the facility to store reclaimed water during the rainy season and retrieve it during the dry season.
“The density of drinking water/freshwater compared to the density of saltwater creates the bubble,” said Phillip Wagoner, chief plant operator at the WRF. “So it’s the difference in density that actually keeps that freshwater together.”
EWD received its full operating permit for ASR in February 2008 and now uses the ASR well on an as-needed basis. “Failure wasn’t really an option here,” McNeal said. “They needed to have a system to work—they were building their reuse system assuming it’s going to work. Without it they would’ve had to put a moratorium out on any more users because, even as it exists now, during the dry season they could probably use much more water than they have available. But with the ASR system, they’ve got twice as much more water available than they would otherwise.”
Throughout the development of its ASR well, other updates also occurred at the Englewood WRF. In 2005, it expanded its capacity to 3 million gal per day (mgd). That expansion project included a new administration/motor control center building that is constructed to withstand a Class 5 hurricane.
Tying it All Together
Raw sewage enters the treatment facility and goes through a settling basin or a settling tank and then is pumped over screens with openings measuring 0.06 in. From the screening, it is pumped into four individual surge tanks, and then pumped into each of four separate extended aeration plants. It then enters an AquaDisk cloth filter and/or a Davco activated carbon traveling bridge filter. Next, it goes through a chlorine contact chamber. After disinfection has occurred, the water is pumped to the 1-mgd reclaimed water storage tank, then to EWD reclaimed water customers or to the ASR well for future sale as reclaimed water.
“We’re a 100% recycling facility,” Wagoner said. “Last year we recovered 112% of our total flow, so we actually were able to recover more than we produced last year.”
Biosolids are pumped from the wastewater treatment plant to the centrifuge and dewatered. Using polymer, the centrifuge removes 98% of the liquid from the biosolids, which are sent to the N-Viro complex in Daytona Beach, Fla., for further advanced treatment, or to the Okeechobee Landfill. The liquid portion is pumped back to the plant for reprocessing.
“Biosolids are taken to a facility that recycles them, turns it into dirt and topsoil for playgrounds and [other similar uses],” Wagoner said.
One to Watch
Now that EWD is fully permitted on its ASR well, McNeal and Wagoner both agreed that other Florida utilities probably will follow suit. “Others certainly have been watching Englewood,” McNeal said. “If Englewood hadn’t walked through that process already, successfully, others would have been sitting back waiting—nobody necessarily likes to be the first. You’ve usually got certain barriers to break down. A lot of times it’s a little tough being out there on the cutting edge, and Englewood has always been a very forward-thinking client. They’re a small utility. I always think of them as a small utility with a very large vision. If it makes sense, they will pursue it.”