Reusing Treated Wastewater at a Texas Business Park: What to Settle Before You Choose a Plant

Yes, treated wastewater can often cover irrigation and, in some cases, fire protection at a Texas business park with no city sewer, but only if you settle what is in the water and where it goes before you pick a plant. On our Live Show we walked through the questions that drive the permit path, the plant type and the cost.

Why not just put in a septic tank?

Septic is the common default, but it does not always work. Some county reviewers are making septic harder because of flows or requirements, and some sites exceed the 5,000 gallons per day TCEQ limit and need a special permit.

Start by asking where the water comes from. Restrooms and break rooms are domestic flow. Tenant operations, such as equipment washing that sends water down a floor drain, are a different stream.

Those two streams can follow different permit paths, so settle both before you choose a plant.

What effluent limit drives the plant and its cost?

In Texas, the number that drives most plants is 30 mg/L of BOD. TCEQ sets the rules for both effluent and reclaimed water.

Limits of 10 or 5 on nitrogen and phosphorus can push you into a mechanical plant, which costs more to build and to run on energy. As limits tighten, the water gets closer to reuse quality.

These are 2026 numbers. An expensive plant runs about $60 per gallon of daily average flow capacity. At the 30 mg/L BOD limit it is closer to $20 per gallon.

On a platted site under common ownership, such as a condo regime, the owners typically own and operate the plant that serves the whole site.

What can reused water be used for, and what must stay potable?

Reuse can serve irrigation, and inside buildings it can flush toilets through purple pipe, which carries reuse water. Anything that touches people, such as drinking, handwashing and food, needs potable water.

We have built dual plumbing systems like this before. Fire protection has its own authority, and the fire code decides what water is acceptable.

I have not had a fire marshal say no to wastewater effluent, but ask early and do not assume. Many sites also fill fire reserves with collected rainwater.

If you want to see how this applies to your site, our developers and builders page covers the work we do for owners like you.

What happens on days you cannot irrigate?

Reuse is not an outlet. A reuse authorization limits when you can land apply, and irrigation cannot take water when the ground is rained on, wet or frozen.

So you need a plan for those days. We often see holding ponds and tanks. TCEQ has water balance calculations for this, and a pump and haul contract is another backup.

Our preliminary engineering reports and TCEQ design submittals work is where that water balance gets built and documented.

What could a tenant send down the drain?

If a plant takes industrial wastewater, ask for its characteristics first: metals, organics, pH and chemicals.

These can kill the biology in the plant. The plant works by adding air to the wastewater so that bacteria can break down the waste, and a harmful discharge can wipe those bacteria out.

For a spec warehouse you may not know the tenant yet. The design basis has to state what the plan assumes and what a future tenant may not discharge. You may also need pretreatment on tenant drains.

A site with offices and distribution only is much simpler.

How do I turn this into a plan my engineer can use?

Write a one-page reuse plan this week. It becomes the basis of a design memo for whoever is designing your plant.

Answer four things: whether the wastewater is domestic or industrial, which reuse you want (irrigation, toilets, fire), where the effluent goes on days you cannot use it, and what keeps the fire tank full.

Fire reserve can be filled by plant effluent, or by a well, rainwater or potable water. With a reuse plant you can route effluent through the fire tank first and then irrigate, or send it straight to irrigation.

Watch the full episode

The full episode is on YouTube: https://www.youtube.com/watch?v=014v2y0t8bk

Frequently asked questions

What limit do most Texas wastewater plants design to?

Most Texas plants are driven by a 30 mg/L BOD limit. Limits of 10 or 5 on nitrogen or phosphorus can push you into a more expensive mechanical plant.

Can treated wastewater flush toilets?

Yes, toilets can run on purple reuse pipe. Drinking, handwashing and food contact must stay on potable water.

Who decides if effluent can be used for fire protection?

The fire code official decides what water is acceptable. Ask them early and do not assume.

I'm a developer planning a flex warehouse park in Texas with no city sewer, and the county is making septic difficult. What should I look at first?

Separate your domestic flow from any tenant process water, since each can follow a different permit path. If flows exceed 5,000 gallons per day, you may need a special permit instead of septic.

I'm building a spec warehouse in Texas and don't know my tenants yet. How do I protect a wastewater plant from tenant discharges?

Put it in the design basis: state what the plan assumes and what future tenants may not send to the plant. You may also need pretreatment on tenant drains.

Related Resources

• How TCEQ Sets Effluent Limits: Understanding Receiving Water Quality Standards and Permit Conditions
• The 330 Day Timeline: Why Texas Wastewater Permits Take Longer Than Developers Expect
• Pretreatment Program Delegation: When a Texas City Runs Its Own Industrial Pretreatment Program Versus Deferring to TCEQ
• OSSF vs. Centralized Sewer: Choosing Between Travis County Septic Permitting and TCEQ Wastewater Permits for Exurban Sites

Need a reuse plan that holds up with TCEQ and the fire office?

We help developers work out the wastewater and reuse design before they commit to a plant. Bring us your one-page plan and we will turn it into a design basis.

We specialize in:

• Wastewater engineering
• Water engineering
• Site civil engineering for land development
• Preliminary engineering reports
• TCEQ design submittals
• Construction administration

Modern Engineering Solutions, McKinney, Texas. Contact: (214) 833-6748 or mod-eng.com