How Much Does a Sewage Treatment Plant Cost?

“How much does a sewage treatment plant cost?”

It depends…

One of the first questions we get asked, is “How much does a sewage treatment plant cost?” That’s a reasonable question. And we love answering it! That’s because our top-quality systems are also some of the least expensive on the market. Don’t believe us? Click the button below to get an estimate for your particular project and then shop around.

Every Aqua Tech system is custom designed around each project. Our sewage treatment plants must meet local design standards while serving the particularities of each application. Factors such as collection type, design flow, and disposal method all play into the system design. And the system design determines the price.

In asking, “How much does a sewage treatment plant cost,” it’s important to remember that size matters.

Wastewater treatment systems, like a lot of other products, are subject to the economy of scale. Price per gallon goes down as the system size goes up.

Like in the diagram, the effect is more pronounced as the system size gets smaller. A 2000 gallon per day system might cost 3x as much per gallon as a 20,000 gallon per day system which might cost 30% more per gallon than a 40,000 gallon per day system.

The economy of scale in this case means that smaller systems require the same planning, design, construction, installation and startup time as do the larger systems. So, if you ask, “How much does a sewage treatment plant cost?” We’ll first need to know, “How big?”

It’s also important to remember that not all sewage is created equal.

Commercial wastewater is typically higher strength than what comes out of your home. RV Parks, for instance can produce raw sewage with a BOD (biological oxygen demand) of nearly 1000 mg/L while concentrations in residential wastewater average around 250 mg/L. Higher strength wastewater requires more biofilm media, larger bioreactors, and bigger tanks to reach mandated effluent limits.

Location (location, location) affects wastewater system price.

Several local conditions such as fast perc rates, high water tables, high quality, or impaired waterways call for stringent treatment levels even for subsurface disposal.

The Chesapeake Bay for instance, has been designated by the EPA as an impaired waterway. That means wastewater discharge in its watershed must be treated to municipal wastewater treatment standards or better.

process flow diagram for an mbbr wastewater treatment plant treating to under 2.5 mg/L TN

This is a process flow diagram for a system to be installed in the Chesapeake Bay Watershed. It requires special appurtenances (add-ons) to ensure reduction of total nitrogen to under 2.5 mg/L.

process flow diagram for an mbbr wastewater treatment plant treating to under 2.5 mg/L TN

That’s a heckuva lot of reduction for a system discharging subsurface.

Sometimes location affects the way treated effluent must be disposed.

The soil in the eastern two-third of Texas, for instance, absorbs very poorly. TCEQ (Texas Commision on Environmental Quality) consequently mandates a soil application rate (SAR) of no more than .1 gallons per square foot per day for subsurface drip disposal systems. That means drip disposal outside the crosshatched counties on this map can cost three times as much as the national average.

TCEQ subsurface disposal guidance map.

Disposal method affects how much a sewage treatment plant will cost.

Aqua Tech’s wastewater treatment technology is so advanced that we also sell surface water discharge systems. With surface water discharge you can do away with a disposal system altogether. That means the system will need to treat to a higher level and include disinfection. But even with those additions, surface water discharge systems price out around 10% less than subsurface disposal systems in most cases.

wastewater treatment tank with integrated controls
The Southside School wastewater treatment reactor with UV disinfector.

Getting there can be half the savings.

The cost of a sewage treatment plant is only part of the overall cost of developing your sewer infrastructure. Sanitary sewers needed to convey the wastewater to the system can cost significantly more than the treatment and disposal systems together. Many Aqua Tech customers have found they can save a ton of money up front and over the long run with STEP Collection. And because STEP Collection eliminates the need for a large settling tank at the treatment works, it can save you money on the treatment system as well.

There’s no fast way to accurately answer, “How much does a sewage treatment plant cost.”

But we don’t mind doing the work to put a free estimate together. Just fill out and submit this form!