Legacy Septic and Excavation thrives on onsite treatment system repairs and replacements. Those projects often involve challenging sites with clay soils or high groundwater where clean effluent is essential. That’s when company co-owner George Schooley looks to aerobic treatment units, typically the Singulair Model TNT (Total Nitrogen Treatment) systems from Norweco.

Schooley, who runs the company in Westminster, Maryland, with his wife Jenny Walsh and a seven-member office and field team, much prefers repairs to installing onsite systems for new homes.

“New construction is not a challenge at all,” he says. “It’s all been laid out for you. It’s all on paper. The repair work is what I love doing. Anything that’s challenging, where somebody says it can’t be done, we can do it.”

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He’s licensed in five Maryland counties and is certified to install drip systems, sand mounds and sand beds. He chooses the 600 gpd Singulair TNT 600 system for homes with up to five bedrooms and the 1,000 gpd Singulair TNT 1000 for larger homes and commercial buildings.

The Singulair Model TNT is designed as a cost-effective treatment system for domestic nutrient reduction, according to the manufacturer. The company reports that certified performance data from NSF International verifies average effluent containing 7 mg/L nitrate, 12 mg/L total nitrogen, 4 mg/L CBOD5 and 9 mg/L total suspended solids. The unit reduces total nitrogen in septic tank effluent by more than 68 percent, the company states. 

The precast concrete unit biologically oxidizes nitrogen compounds to accomplish nitrification and denitrification without requiring costly and complex equipment. It is designed for simple operation and maintenance and does not require chemical addition or effluent recirculation. It provides surge flow equalization and effluent filtration with low electricity usage. All treatment is accomplished within the precast concrete tank.

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Treatment is accomplished by an extended aeration process. Biological reduction of nitrogen is accomplished by autotrophic bacteria that convert ammonium nitrogen to nitrate and heterotrophic bacteria that transform nitrate to nitrogen gas.

Septic tank effluent first enters a pretreatment chamber where solids settling and flow equalization occur. Effluent then enters a chamber employing a mechanical aerator and undergoes biological treatment.

The final step is in a clarification chamber that consists of five functionally independent zones that operate together to maximize settling of solids into a hopper. A sludge return system on the wall between the aeration and clarification chambers returns settled solids to the aeration chamber to sustain the biological process.

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An electrical control center provides monitoring, compliance and diagnostic functions.


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