Optimizing Water Use
Water is an essential natural resource and an important input to our materials management processes. We work to minimize freshwater use and wastewater discharge in our own operations by recycling and reusing water. In addition to environmental benefits, these efforts frequently help us reduce costs. In addition, as part of the environmental solutions we offer to our clients, we recycle millions of gallons of wastewater through pretreatment and discharge to publicly owned treatment works (POTWs) every year.
Water Use at Our Facilities
WTE facilities use water to generate electricity. In the boiler, water is heated to generate the steam needed to run the turbine and generate electricity. Most of the water used in this process is condensed and reused in our power-generation processes. At some of our plants, steam is exported to communities and local businesses to supply heat and cooling. While that export process allows for high thermal efficiencies, we cannot capture all water condensed after leaving our facility and must add water to replace the lost condensate.
In many cases, our facilities generate electricity in a combined heat and power arrangement.
- Our Niagara Falls facility exports steam to a local industrial park, which houses a paper mill that produces 100% recycled paper.
- Our Indianapolis facility exports steam to the City of Indianapolis’ downtown steam loop, which provides heat and cooling energy for residential and commercial buildings, including a major hospital.
- Our Huntsville facility supplies steam to the Redstone Arsenal.
Facilities with turbine generators will generally have a condenser to return the steam from the turbine back into water for reuse in the boiler. The condensers may be cooled with water or air. About 75% of our WTE facilities use water in cooling towers. Water-cooled condensers are either recirculating cooling towers or once-through systems. We operate two once-through cooling plants, both of which use non-potable saline water. We continue to increase the use of alternative, non-potable sources of freshwater at our facilities while decreasing the use of freshwater.
In addition, we use water at our WTE facilities for ash quenching, a process by which non-hazardous ash is sprayed with water following the waste combustion process to reduce dusting.
In addition to minimizing our water consumption, we also minimize our wastewater discharge by reusing water internally as much as possible, typically by using wastewater from one process as feedwater in another process. For example, cooling-tower blowdown water, a water stream extracted from the cooling-tower system to prevent the build-up of salts, is often used to help quench the ash after the combustion process. Nineteen Covanta facilities are zero-process-water-discharge facilities, meaning that only sanitary wastewater is discharged to the local wastewater treatment plant.
Our SEMASS facility is unique in that it filters its own drinking water for employees and visitors. The facility is far enough away from municipal water systems that the plant installed their own utility. The system is regulated and tested by the state like any large-scale water system. In fact, the SEMASS system was ranked in the top 12% of all systems within the state in 2019.