The Hidden Costs of Replacing a Lagoon with a Mechanical Plant

When confronted with new effluent limits, many municipalities feel their only option is to scrap their otherwise adequate lagoon system and replace it with a mechanical treatment process, like an activated sludge, SBR, or MBBR plant. There’s a better option: A lagoon can be upgraded to remove ammonia and phosphorus, treat BOD and solids, and produce an effluent quality as good as a mechanical plant—at a fraction of the cost.

In addition to the capital expense, there are many hidden costs to replacing a lagoon with a mechanical plant. At the lagoon optimization workshop we hosted in Adel, Iowa, last May, we took a few minutes with instructor and lagoon expert Steve Harris of H&S Environmental to get his take on why Lagoons Do It Better. In this video, he discusses some of the unexpected costs associated with mechanical plants. Watch the video, and read on below for highlights of the conversation.

Lagoons Can Do the Job

As Steve explains in the video, most lagoons were built decades ago, before engineers had a good handle on the mechanisms of lagoon treatment like hydraulics and the interplay of the biological and chemical processes. Through scientific research over time, we’ve learned how to overcome some of the inadequacies that were built into lagoon facilities.

replacing a lagoon with a mechanical plant

Add NitrOx to a lagoon to treat ammonia.

Steve’s process as a lagoon consultant is to systematically evaluate a lagoon and diagnose the source of issues, starting with free or inexpensive fixes. Something as simple as repositioning aerators can solve a short-circuiting problem and improve BOD treatment, for example.

Nutrients can be treated with the addition of a tertiary process like Triplepoint’s NitrOx® Lagoon Ammonia Reactor or PhosBox™ Phosphorus Removal. Upgrading a lagoon allows you to keep your existing infrastructure and its ease of operation and achieve single-digit BOD and TSS, and nutrient levels lower than 1 mg/L.

Replacing a Lagoon with a Mechanical Plant: Other Costs to Consider

The construction of a new mechanical plant costs several million dollars. Municipalities with smaller populations don’t have the user base to support a multimillion dollar capital expense. While grants may cover a portion of the cost, the municipality is on the hook for the rest. A low-interest loan from a state revolving fund may put this expense within reach, but there are other costs involved when replacing a lagoon with a mechanical plant:

  • Operations: The operation of a mechanical plant requires a higher level of certification than a lagoon. Will you be able to train or find enough qualified operators or will you have to hire outside contractors?
  • Electrical costs: A mechanical plant consumes more energy than an aerated lagoon. Will your municipality be able to cover higher electric bills?
  • Maintenance: Mechanical plants require ongoing maintenance—solids handling, desludging, and wasting; and the replacement of components like pumps. Steve tells of his personal experience with a small rural community saddled with an activated sludge plant. They were unable to afford monthly solids handling and ended up with six or seven feet of sludge in the reactor and foaming from an overgrowth of Nocardia bacteria.

Be Careful What You Wish For

A small western town with a population of less than 3,000 decommissioned their lagoon system and replaced it with a 200,000 gpd mechanical plant. The $5 million price tag was financed largely by grants, with the town taking on a $1 million loan to pay the rest.

A public works official with the town related to us that the ongoing costs are unmanageable: In addition to the loan payment, the town is also facing a monthly power bill of over $3,500–more than $40,000 per year. Furthermore, they have been unable to locate an operator with the required certification level to run the plant for the available salary. For a town with a small user base, that level of investment is unsustainable. “Be careful what you wish for,” said the town official. “Everyone was happy that we qualified for funding to build the plant, but we’re finding it requires more people, money, and power to operate, none of which we have.”

Pickup Truck vs. Ferrari

As Triplepoint’s Brady O’Leary puts it, a small town needs the wastewater equivalent of a pickup truck: easy to operate and work on and reliable. An activated sludge plant is like a Ferrari, far more complicated and expensive. It’s a great piece of machinery, but much more demanding and expensive to keep running.

Give Your Lagoon a Chance

replacing a lagoon with a mechanical plantAs Steve says in the video, give your lagoon a chance! Before contemplating scrapping your lagoon system, find out what your options are.

Contact Steve Harris at H&S Environmental; we consider him the Delta Force of wastewater lagoon troubleshooting and optimization. He wrote the book on lagoon operations and it’s our go-to resource.

Also, call Triplepoint at 800-654-9307! We believe in lagoons: it’s all we do. We’re happy to talk to you about your lagoon challenges. Request a free, no obligation quote for MARS Aeration or our NitrOx Lagoon Ammonia Removal System.

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