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Problem

The developers of a slow build-out, 750-home lakeside subdivision in rugged terrain had a challenging problem. They needed a modular, build-as-you-go wastewater solution for this community of full- and part-time residents that could consistently meet the stringent (20 mg/L) nitrate requirements set by the Tennessee Department of Environment and Conservation, in spite of highly variable flows. Connecting to an existing municipal treatment plant was not an option, since the nearest plant was 20 miles (32 km) away. Standard septic systems could not be relied on to meet the stringent nitrate requirements, and many of the lots were not large enough (or were too close to the reservoir) to use an onsite advanced treatment system.

Solution

The developers — together with Environmental Systems Corporation (engineers) and Orenco Systems® (wastewater equipment designers and manufacturers) — conceived of an innovative effluent sewer system for this high-end subdivision. The effluent sewer system includes a tank at each lot to collect household wastewater, as well as an advanced treatment unit (an AdvanTex® AX20 or AX20-RT Treatment System) that produces TN of <20 mg/L. The treatment unit then pumps this highly treated effluent through small-diameter collection lines to a drip field dispersal system that serves the entire subdivision. The system has a design capacity of 165,000 gpd (625 m3/d), is maintained by a local utility (Hallsdale-Powell), and is outperforming all permit requirements.