The Ohio Environmental Protection Agency has released a draft wastewater discharge permit for a proposed data center project — one of the clearest signals yet that state regulators are paying closer attention to what comes out of these facilities, not just how much water goes in.
The draft National Pollutant Discharge Elimination System (NPDES) permit outlines effluent limits, monitoring requirements, and reporting obligations tied to wastewater generated from cooling operations. It’s subject to public review and comment before finalization, and it could set a template for how other states approach data center wastewater regulation.
Why Data Centers Produce Wastewater
Most people think of data centers as purely digital operations. The reality is far more industrial. Hyperscale data centers — the massive facilities operated by companies like Google, Microsoft, Amazon, and Meta — generate enormous amounts of heat from the servers running inside them. That heat has to go somewhere.
The most common cooling approach is evaporative cooling, which works essentially like a giant swamp cooler. Water circulates through cooling towers, absorbing heat and evaporating into the atmosphere. The process is effective but water-intensive — a single large data center can consume 3 to 5 million gallons of water per day.
But evaporation isn’t the only water concern. The cooling process concentrates dissolved minerals and treatment chemicals in the remaining water, which must eventually be discharged as “blowdown” wastewater. This discharge can contain elevated levels of:
- Total dissolved solids (TDS) from mineral concentration
- Biocides and anti-scaling chemicals used to prevent biological growth and mineral deposits in cooling towers
- Chromium and zinc from corrosion inhibitors (in older systems)
- Elevated temperatures that can affect receiving water ecology
What the Ohio Permit Requires
The draft NPDES permit establishes specific conditions designed to meet Clean Water Act standards:
- Effluent concentration limits for key pollutants in cooling tower blowdown
- Sampling protocols requiring regular monitoring at discharge points
- Thermal discharge limits to protect downstream aquatic life
- Reporting requirements that create a public record of discharge volumes and quality
- Compliance conditions that could trigger enforcement if limits are exceeded
The permit applies specifically to wastewater generated from cooling operations and related processes — not to stormwater or sanitary wastewater, which are regulated separately.
A Growing Regulatory Trend
Ohio isn’t alone in scrutinizing data center water use. In February 2026, Texas regulators announced they would require data centers to report water usage starting this spring. In January, U.S. Representative Robert Menendez introduced a bill to regulate data center energy generation and monitor water use at the federal level.
The attention reflects the sheer scale of data center expansion. According to industry estimates, U.S. data center capacity is expected to more than double by 2030, driven by AI workloads that require significantly more computing power — and therefore more cooling — than traditional cloud services.
For communities near proposed data center sites, the water question is increasingly personal. When a single facility can consume as much water as a small city, residents and local officials want to know: what happens to that water, and what condition is it in when it comes back?
The Groundwater Connection
While this permit specifically addresses surface water discharge, the data center water issue has direct groundwater implications:
- Aquifer drawdown: In areas where data centers source water from groundwater wells, heavy pumping can lower water tables and affect nearby private wells
- Discharge infiltration: Depending on local geology, treated wastewater discharged to streams can infiltrate into shallow aquifers
- Competing demand: Data centers compete with agricultural, municipal, and residential users for the same water resources — a tension that’s especially acute in drought-prone regions
The NGWA has specifically addressed the role groundwater professionals play in meeting data center cooling needs, recognizing both the opportunity and the responsibility the industry faces as data center construction accelerates.
What to Watch
This Ohio draft permit is a leading indicator. As more states grapple with data center expansion, expect:
- More detailed NPDES permits with facility-specific effluent limits
- Water use reporting mandates that create transparency around consumption
- Groundwater monitoring requirements near data center sites that use well water
- Public opposition in water-stressed communities, potentially slowing or redirecting projects
- Industry innovation toward less water-intensive cooling technologies, including liquid cooling and heat recovery systems
The public comment period for the Ohio permit provides an opportunity for residents, environmental groups, and water professionals to weigh in on whether the proposed limits adequately protect water quality.
If you’re concerned about how a proposed data center or industrial facility might affect your local water supply, a certified water treatment professional can test your well water and advise on appropriate filtration or treatment options.