Using an Advanced Reuse Solution for Cooling Tower Makeup Water
A packaged filtration system saves more than 1 million gallons of water per day for a Pennsylvania power plant.
Water treatment technologies such as reverse osmosis and ultrafiltration are not new. For years, municipalities, commercial entities and even homeowners have been employing these technologies to help purify water. But, as economic growth and water scarcity issues cause mounting pressure on the water infrastructure, more industrial water consumers are looking at how these technologies can aid in their water reuse efforts.
For many industries, reusing water means transforming low quality wastewater and feedwater into high quality water for use in process heating or cooling applications. It is a growing global trend that provides economic benefits for companies.
One such company that sought those benefits is Covanta’s Delaware Valley energy-from-waste facility in Chester, Pa. The facility generates up to 80 MW of clean energy from up to 3,510 tons per day of municipal solid waste. Prior to November 2014, the plant was using 1.3 million gallons a day (MGD) — or nearly 5 million liters a day — of municipal drinking water in its waste-conversion process, costing the company thousands of dollars in daily water purchases.
|See the related web exclusive, "Combination Ultrafiltration and Reverse Osmosis Skid Provides Tertiary Treatment," for an overview of the benefits of using a skid-mounted combination tertiary treatment package.|
To reduce facility operating expenses and the consumption of local water resources, Covanta worked with GE Water & Process Technologies to develop an advanced water reuse solution for Covanta’s cooling tower makeup requirements. The facility wanted to use treated discharge water from a nearby Delcora municipal wastewater treatment plant. (The Delaware County Regional Water Quality Control Authority, or Delcora, owns and operates several water pollution control plants throughout Pennsylvania.)
For the water reuse project, Covanta uses tertiary wastewater from the Delcora municipal wastewater plant as the source water for its cooling tower makeup. This allows Covanta to reuse water that would have been discharged and eliminates the need to use potable drinking water.
The typical organic and dissolved mineral content in the water provided by Delcora means that the water requires additional treatment for it to be suitable for Covanta’s Delaware Valley cooling tower application.
With extensive experience in the design, installation, operation and maintenance of membrane water and waste treatment systems, the engineers at GE were confident they could develop a water treatment solution for Covanta. A comprehensive assessment determined that reverse osmosis (RO) with ultrafiltration (UF) pretreatment would provide the most effective results. The ultrafiltration stage prior to reverse osmosis treatment would prefilter the organic material and suspended solids content in the water and optimize the filtration system operation. The reverse osmosis system would provide the low total dissolved solids (TDS), high quality water needed for the cooling towers.
Once the water treatment solution was defined, GE selected its RePak combination UF and RO as a tertiary treatment package for Covanta. The RePak product line is designed for tertiary wastewater applications. RePak integrate GE’s ZeeWeed 1500 pressurized UF modules and Pro Series low fouling RO elements on a common skid. The solution also includes integrated controls and a common buffer, backwash and clean-in-place (CIP) tank. Combining systems reduces the equipment footprint. It also reduces capital costs and field installation expenses when compared to the use of separate UF and RO systems with multiple process and cleaning tanks.
GE supplied Covanta Delaware Valley with two RePak-450 trains that each produce 450 gal/min of purified water. Each train uses a single multifunctional tank for break, UF backwash, UF CIP and RO CIP, which greatly reduces the footprint needed for the system.
With installation and commissioning complete in 2014, Covanta became the first North American industrial company to deploy GE’s RePak technology.
Water Purchases, Expenses Cut
For Covanta, GE’s RePak solution has allowed the reuse of 1.3 million gal/day of treated discharge water for cooling tower operation. The water treatment solution eliminated the need for the facility to purchase water from other sources. In addition to favorable environmental benefits, Covanta enjoys a daily purchased-water-charge savings of nearly $4,000.
“By installing GE’s water treatment technology, we are able to reuse the nearby wastewater treatment plant’s wastewater effluent that otherwise would have been directly discharged, enabling us to save over a million gallons per day in drinking water for local residents rather than using it for industrial purposes,” says Tim Gregan, the facility manager at Covanta Delaware Valley. “We [are] reducing the stress on local drinking supplies [and] also the environmental impacts of the wastewater treatment plant and the use of potable water by our facility.”
Increasing regulations and the cost of fresh-water sources likely will drive more North America industrial facilities to look at water reuse opportunities. Saving 1.3 million gallons of water and $4,000 daily are results that will get industrial water consumers thinking about the changes they can make to evoke such environmental and financial benefits.