October 7, 2026

Data Center Insights: Dealing with the Wastewater

As communities continue grappling with whether and how they want to accommodate large new data centers, it’s essential to consider the full water cycle.

Data centers require water for cooling because of the heat they generate. Communities are right to want to understand a proposed facility’s water source plans: tapping potable (or drinkable) supplies; purchasing municipal reused water that’s been treated for industrial purposes; or using a closed-loop system that recycles a finite supply.

But any use of water produces some type of wastewater, and that raises a variety of considerations for utilities to keep in mind.

What cooling technology will the data center use?

How will the load on your community’s wastewater treatment system increase?

The impact a data center has on your community’s wastewater treatment system depends on the facility’s location, size, cooling technology type and the influent water source (e.g., potable water vs. recycled wastewater subjected to tertiary treatment).

Data center wastewater can be characterized by low organic loading (BOD), high total dissolved solids (TDS), elevated temperatures, residual chemicals, biocides, glycols, PFAS, bromine, refrigerants and high hydraulic loading (volume). Therefore, the impact on your municipal collection and treatment system is primarily driven by high temperature loading, elevated TDS levels, possible chemical toxicity and the intermittent discharge of large wastewater volumes. If left untreated prior to discharge, these contaminants could create significant operational and compliance challenges for your municipal wastewater collection systems and treatment plants.

Data center wastewater volume that is disproportionately large compared to the normal waste flow from your community itself would have an outsized impact. Because of that, many municipalities now require data centers to install on-site pretreatment facilities and obtain industrial wastewater discharge permits.

A plant that exceeds its wastewater discharge permit limits because of a data center can be subject to a notice of violation, fines and other administrative actions. The EPA’s national industrial pretreatment program prevents the discharge of pollutants into POTWs or community wastewater treatment systems that will interfere with operations or pass through the treatment processes. Local POTWs and state environmental agencies are responsible for implementing and enforcing mandatory pretreatment programs.

If a data center discharges its wastewater directly into the environment (such as surface water), it is considered a direct discharger and must follow its National Pollutant Discharge Elimination System (NPDES) permit requirements.

• Data centers create high peak demands that can exceed the capacity of your wastewater treatment plants or water reclamation facilities, particularly during the summer in water-scarce regions.

• If a data center’s on-site wastewater pretreatment plant fails to meet regulatory discharge limits such as those for thermal loading, TDS, chemicals of concern and pH, it can create major operational and compliance risks for your POTW receiving the wastewater. These risks are mitigated if the data center has an effective on-site wastewater treatment plant and holds its own direct discharge permit.

• Using recycled water encourages utilities to invest in building out purple pipe reclaimed water systems or non-potable water reuse distribution systems directly to the data center.

• What are the average daily flow, maximum flow and peak water demands during the summer?
• What are the data center’s estimated annual water demand and expected average and maximum wastewater discharge quantity? Does this change in the next 5-10 years?
• What are the maximum and lowest temperatures of generated wastewater on site?
• What are the average and maximum levels of TDS, minerals, chemical oxygen demand (COD), pH, other residual chemicals concentration and bacteria in the wastewater?

Here are questions to ask about your utility’s system:

• Does your collection system have adequate capacity to convey the additional wastewater discharge?
• Does your wastewater treatment plant have adequate capacity within your NPDES permit to accept the discharge?
• Do you have an Industrial Pollution Pretreatment Program? If so, does it identify surcharge limits for likely contaminants such as TDS, minerals, COD, pH or other chemicals?

Freese and Nichols does not design data centers, but we have extensive experience in water/wastewater system planning, industrial reuse applications and water/wastewater treatment planning and design.

We also help utilities develop and maintain industrial pollution prevention programs, including program development, ordinances and developing surcharge fees for industrial dischargers.

Our Water Resources Planning, Water/Wastewater Planning, Environmental and Treatment teams are best equipped to help water utilities, municipalities and counties manage issues associated with data centers, size appropriate facility expansions and manage industrial wastewaters.