Regulating AI Data Center Wastewater in Ohio: Ohio EPA Considers Permitting Discharges into Surface Waters Under NPDES Rules, Public Concerns, and Wastewater Management Trends

     The Ohio EPA is considering regulating data center wastewater under the National Pollutant Discharge Elimination System (NPDES), which permits wastewater discharge into local waterways. They are developing a general wastewater permit for new data centers. They have recently extended the public comment period to January 16, 2026, having already received 4000 comments. Amy Swank, a Dublin resident and advocate for community concerns regarding data centers, noted:

“I think there are real concerns about what could be in the water,” said Swank. “Data centers use massive amounts of water to cool their systems and all of that water is run through pipes that could be treated with anti-corrosives. Because we are talking about a permit for hypothetical data centers with hypothetical HVAC systems, how can we even know what will be in the water?”

     The draft permit covers both wastewater and stormwater from the facilities, but does not include sewage effluent or process water.

“Wastewater discharges include non-contact cooling waters (once through or re-circulated water that does not come into contact with the process operations of a facility and is used only to convey heat from the facility), low volume wastewaters (such as, cooling tower blowdown, boiler blowdown, and air compressor condensate yet excludes some waste streams like sanitary wastes) and stormwater associated with the industrial activities from the site.”

     In more detail, from the draft permit, the following wastewater sources are eligible under the permit:

a. "once through cooling water" (e.g., the water passed through a cooling system for the purpose of removing unwanted heat), or “recirculated cooling water” (e.g., the water that is passed through a cooling system for the purpose of removing unwanted heat and then recycled back through the cooling system for reuse). This discharge may result from a variety of heat transfer systems designed to remove unwanted heat as a result of industrial activities;

b. low volume wastewater discharges to waters of the state, including but not limited to, cooling tower blowdown, boiler blowdown, and air compressor condensate (See Part VI of this permit for a definition of low volume wastewater including those wastewaters that are excluded), and;

c. stormwater associated with the industrial activities (See Part VI), including but not limited to, generators, fuel and chemical storage tanks, outdoor equipment storage, and material loading/unloading areas.

     Sources not covered include wastewater under an existing NPDES permit, discharges within 500 yards upstream of a public drinking water source, and discharges into the Ohio River that do not meet water quality standards at the point of discharge, discharges directly to groundwater, or discharges into lakes other than Lake Erie. The WDTN Dayton report by Jesse Bethea notes that the Ohio EPA acknowledges a “lowering of water quality” will occur with data center development, yet another thing “the people” will have to accept with data center development:

“The EPA’s draft permit acknowledges, “a lowering of water quality of various waters of the state associated with granting coverage under this permit is necessary to accommodate important social and economic development in the state of Ohio.”

     However, an Ohio EPA spokesperson said the above wording is the same for any NPDES permit, including those for a school or a campground. However, I also know from working with some NPDES permits that those for campgrounds, especially, may include sewage effluent, although that will not be the case for data centers. It should also be noted that other states are also utilizing NPDES permits for data center wastewater discharges, so Ohio is not out of the ordinary here.

     Commenters in the WDTN Dayton article mostly wanted the EPA to slow down and consider each case longer, and others questioned why a new kind of permit would be required. Wastewater generation is certainly a valid concern with data centers, as is water consumption, both of which are significant in terms of volumes.

 

The Importance of Data Center Wastewater Management and Monitoring

     Below are some considerations of data center wastewater management from a Microsoft Copilot search:

     KETOS, a company that provides digital water quality monitoring, notes:

“We postulate that the rise in AI-driven water usage will inevitably lead to an astonishing increase in wastewater discharge, which has profound implications for water quality, public health, and carbon emissions.”

      They also note the need for real-time water quality monitoring at data centers. KETOS monitors for 35 contaminants and parameters, including nitrates, pH, conductivity, heavy metals, inorganics, and oxidation-reduction potential. They noted in 2024 that wastewater discharges from data centers were being overlooked. Some of the wastewater will need to be treated at local water treatment plants. However, large volumes could strain those plants. Both larger volumes of wastewater and, in some cases, higher concentrations of contaminants are concerning.

     Below, Ganesh Hegde of KETOS explains the difference in water use and wastewater discharges between conventional cloud computing data centers and AI data centers.

“Unlike conventional data centers, AI-focused data centers have significantly higher power density and, therefore, higher cooling requirements. Water has a significantly higher heat absorption capacity than air and is favored over other options that remain costlier. This makes it so that, even with a variety of cooling solutions at a data center’s disposal, the higher use of power is leading to an increase in water consumption and wastewater discharge.”

“Data centers by their nature produce a significant amount of heat, requiring effective cooling to maintain optimal operating temperatures. Conventional data centers typically use air-based cooling systems, which are cost-effective and easy to implement but less efficient for high-density environments. AI data centers, however, necessitate more advanced cooling techniques due to their higher heat output. This has led to a rise in liquid-based and hybrid cooling systems.”

     Below, Hegde explains that water use efficiency (WUE) is a useful metric, but also one that is site-specific.

“According to our calculations, the industry should anticipate an additional 100 billion gallons of wastewater annually originating from the cooling demand of AI data centers (in an optimistic scenario of only WUE = 1.0).”

“AI data center power demand is expected to equal conventional data center power demand by 2028. Therefore, it’s safe to expect an additional 100 billion gallons of wastewater due to net data center cooling demand from hybrid cooling alone.”

     Also of significant concern is that data centers are expected to double the volume of wastewater being treated at some wastewater treatment plants. That could cause some problems for those plants that need to be considered.

     Below are some trends toward addressing data center wastewater, including WUE calculation requirements and closed-loop water systems that reduce evaporation.

 

 

References:

 

Public Comment Form: Draft Wastewater General Permit for Data Centers. Identification Number(s) OHD000001. Action Date: October 9, 2025. Ohio EPA.  Draft Wastewater General Permit for Data Centers

OHIO ENVIRONMENTAL PROTECTION AGENCY GENERAL PERMIT AUTHORIZATION FOR DISCHARGES FROM DATA CENTER FACILITIES UNDER THE NATIONAL POLLUTANT DISCHARGE ELIMINATION SYSTEM. Ohio EPA. OHD000001_Draft.pdf

Ohio EPA considers allowing dumping of wastewater into bodies of water. Jesse Bethea. WDTN Dayton. December 24, 2025. Ohio EPA considers allowing dumping of wastewater into bodies of water

Discharge from AI Data Centers and How to Mitigate Contamination. Ganesh Hegde. KETOS. July 24, 2024. Discharge from AI Data Centers and How to Mitigate Contamination

AI Data Centers, Wastewater Discharge, and the Growing Need for Effective Water Management. Ganesh Hegde. KETOS. July 10, 2024. AI Data Centers and Wastewater: Smarter Water Management | KETOS

Conventional vs AI Data Center Cooling Options and How Much Wastewater is Being Generated. Ganesh Hegde. KETOS. July 17, 2024. Conventional vs AI Data Center Cooling and Wastewater | KETOS