New Power Plants Need More Than Fuel and Transmission. They Need a Water Strategy.

Water supply, treatment, cooling, and reuse belong in the earliest stages of power plant planning

U.S. electricity demand is expected to keep rising through 2027, according to the Energy Information Administration. Meeting that demand will require additional generating capacity, along with fuel, transmission access, and suitable sites. For new steam power plants, water availability and quality can be just as consequential. Steam-cycle projects have several important considerations during early development: whether sufficient water is available, whether it can be treated to meet plant requirements, and how wastewater will be managed.

Developers of steam-electric generating facilities need to verify that local water resources can reliably provide sufficient water at the required quality. They must also consider how water will be managed after use, making water infrastructure an important part of early project planning.

The Water Balance Depends on the Plant

Water demand varies depending on generating technology, cooling configuration, local climate, and operating schedule. Combined-cycle plants use exhaust heat from a combustion turbine to produce steam for a second turbine, creating water requirements beyond those of a simple-cycle gas turbine.

In a steam plant, cooling often accounts for a significant portion of water use, with volumes largely dependent on the cooling system. Water withdrawal refers to the total volume taken from a source, while water consumption is the portion not returned to that source, such as water lost through evaporation. Once-through cooling withdraws large volumes of water, typically from a surface water source, and returns most of it to the source, while recirculating wet cooling reuses cooling water, substantially reducing withdrawals.

Beyond cooling, water is also needed for boiler feedwater, equipment cleaning, and other plant processes, with quality requirements varying by application.

Cooling Choices Change the Equation

Once-through cooling generally withdraws surface or groundwater, passes it through the cooling system, and returns most of it to the environment, so while a plant may withdraw a great deal of water, consumption may remain comparatively low. Once-through cooling may, however, require withdrawals that exceed regulatory limits or raise environmental concerns at the intake or outfall. Thermal pollution, specifically, can affect aquatic ecosystems and impose additional permitting requirements.

Wet recirculating systems reuse cooling water in towers but lose water through evaporation, drift, and blowdown. They generally withdraw less than once-through systems, yet evaporation can make consumption more significant.

Dry cooling, on the other hand, rejects heat to the air and uses much less cooling water, with potential penalties in capital cost and plant efficiency, particularly during hot weather.

Hybrid systems combine wet and dry approaches to balance water savings against performance.

The appropriate choice of technology depends on available water, climate, operating economics, site conditions, and applicable permits. It can also influence the size and cost of water treatment infrastructure, the volume of wastewater generated, and the permits required for plant operations.

Water Quantity Is Only Half the Supply Question

Cooling towers face challenges from scaling, corrosion, and biological growth. As water evaporates, dissolved minerals remain and become more concentrated. Operators discharge a portion as cooling tower blowdown and replace it with makeup water to manage those concentrations. The minerals and other contaminants present in source water determine the treatment needed to make it suitable for plant operations. They also influence chemical consumption, the amount of makeup water required, and the volume and composition of wastewater streams.

Boiler feedwater typically demands much tighter control of dissolved solids and other contaminants than cooling makeup because steam systems are particularly vulnerable to scaling, corrosion, and deposits. Treatment may include traditional or membrane filtration and additional polishing. Seven Seas Water Group offers water treatment technologies for industrial supplies, including brackish water reverse osmosis desalination and high-purity applications.

Evaluating source water quality early helps developers identify the treatment processes needed to meet the specific requirements of each plant application.

When Freshwater Is Not the Best Source

In regions where freshwater supplies are limited or already under pressure from municipal, agricultural, and industrial demand, securing sufficient water for a new power plant can present challenges. Even when a source is available, withdrawal restrictions, treatment requirements, and the cost of connecting to that source can affect its feasibility.

Depending on local conditions, alternatives may include reclaimed municipal wastewater, treated industrial wastewater, brackish groundwater, and other nonpotable sources. Each option must be evaluated for availability, water quality, treatment requirements, and applicable permits.

Reusing municipal wastewater, for example, may provide a supplemental water source for power plants while reducing demand on conventional freshwater supplies. Depending on local conditions, this approach can also create opportunities for partnerships between power plant developers and nearby communities. Reusing suitable water streams within the facility can further reduce freshwater withdrawals.

Reclaimed water generally needs additional treatment before use in a cooling tower, brackish groundwater may need desalination, and water destined for a high-purity steam system can require more extensive polishing. A fit-for-purpose approach tailors source water treatment to each application, delivering the required water quality without wasting money on superfluous treatment.

Plan for What Leaves the System

Cooling tower blowdown, boiler blowdown, membrane concentrate, water-treatment residuals, and other process wastewater vary in volume and composition, which can affect discharge routing, treatment requirements, and permitting strategy.

As water moves through cooling and treatment processes, dissolved minerals and other contaminants can become more concentrated. This can increase the treatment needed before wastewater can be discharged or reused, making wastewater management an important consideration when selecting the original water source.

Reuse can reduce not just withdrawals but also discharges. Suitable process streams may be treated and reused, and some wastewater can be recycled as cooling makeup. Seven Seas designs and operates wastewater treatment and reuse systems tailored to the requirements of each application. Across its portfolio of water and wastewater facilities, the company reports an average plant availability of 98.7%.

How Much Water Can Be Recovered and Reused?

More water recovery isn’t always better. As plants seek to reuse a greater share of their wastewater, the cost and complexity of treating what remains can increase.

As more water is recovered, dissolved minerals and other contaminants can become increasingly concentrated in the remaining wastewater. Additional treatment may be needed to manage these constituents, potentially increasing energy consumption, operating costs, and residuals management requirements.

The appropriate level of recovery depends on the source water quality, intended reuse application, treatment technology, and overall project economics. Rather than maximizing reuse in every situation, the goal is to identify a practical balance between water conservation, treatment requirements, and long-term operating costs.

Water Decisions Can Shape the Power Plant

Water availability and quality can influence decisions well beyond the treatment system itself. A limited water supply may affect site selection or cooling technology, while challenging source water conditions may require additional treatment infrastructure. Wastewater discharge requirements can also influence plant design, permitting, and operating costs.

These considerations have scheduling implications as well. Developing a new water source, constructing pipelines, securing permits, or building dedicated treatment capacity may require substantial lead time. Evaluating these requirements early allows developers to incorporate water infrastructure into the broader project design and construction schedule.

Put Water Infrastructure on the Generation Schedule

When conventional water supplies cannot support a new power plant, developers may need dedicated treatment infrastructure, alternative water sources, wastewater reuse, or a combination of approaches.

Seven Seas works with industrial customers to develop and operate dedicated water and wastewater infrastructure through long-term partnerships. Its Industrial Water-as-a-Service (iWaaS™) model provides a way to secure treatment capacity without the upfront capital investment or ongoing responsibility of owning and operating the infrastructure. Seven Seas handles design, financing, construction, operations, maintenance, and repairs, allowing power plant developers to focus their resources on generation.

Planning water infrastructure alongside the generation facility helps ensure that the project has a strategy for delivering the required water quality, managing wastewater, and supporting operations throughout the plant’s service life.

Contact Seven Seas to discuss how a comprehensive water strategy can support your power generation project from initial planning through long-term operations.

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