Between the Lakes - An innovative onsite system serves a condominium and housing project on a popular chain of lakes in a Wisconsin resort community - Case Study
- Location: Three Lakes, Wis.
- Facility served: Condominium and housing project (total 267 bedrooms)
- Designer: Baudhuin Inc., Sturgeon Bay, Wis.
- Installer: Bergeman Plumbing & Heating, Chippewa Falls, Wis.
- Site conditions: Level; stratified sand soil with loading rate of 1.6 gpd per square foot; seasonal high groundwater 8 to 9 feet below surface.
- Type of system: Aerobic treatment with pressure distribution.
- Hydraulic capacity: 45,000 gpd.
The Burnt Rollways Reservoir, a chain of 20 lakes in Northern Wisconsin, is a prized recreational resource for Oneida County and the community of Three Lakes. The Northernaire, a large housing development near two lakes on the chain, raised concern when it was proposed several years ago.
This high-density development in a resort area several miles from the nearest municipal treatment plant needed an effective onsite system to protect groundwater and the lakes. Baudhuin Inc., an engineering firm in Sturgeon Bay, Wis., designed the treatment system to accommodate upscale condominiums and cottages with a total of 267 bedrooms and a design flow of 45,000 gpd.
The system is built around four aerobic treatment units and two pressure-distribution, demand-dosed drainfields with a total of 48, 4-foot-wide trenches, a combined 7,200 feet long and comprising 28,125 square feet. Bergeman Plumbing & Heating Inc., Chippewa Falls, Wis., is the installer for the system, which is being built in four phases to coincide with the pace of home sales in the project.
The site for the treatment system was wooded and had to be cleared and grubbed. The terrain is level; the soil is stratified sand with a loading rate of 1.6 gpd per square foot. Seasonal high groundwater lies at 8 to 9 feet below the surface.
The Northernaire development is now under construction near Three Lakes, Wis. (Photos are courtesy of Baudhuin Inc.)
When the system is completely built out (all four phases installed), its major components will include:
- Four FAST 9.0 aerobic treatment units from Bio-Microbics Inc., Shawnee, Kan.
- Two 18,000-gallon trash tanks, three 18,000-gallon surge/ recirculation tanks, four 9,000- gallon ATU tanks, one 6,000- gallon triple-compartment effluent filter/splitter tank, two 2,500-gallon lift stations, one 2500-gallon dose tank, and one 3,000-gallon dose tank, all from Wieser Concrete, Portage, Wis.
- 4 x 7,200 feet of EZflow drainfield media, Ring Industrial Group, Oakland, Tenn.
- Two Orenco 1554 effluent filters, Orenco Systems Inc., Sutherlin, Ore.
- 14 Goulds pumps, all 1 hp.
- 72 ball valves (squirt valves for effluent distribution)
- 26 drainfield chambers (for ATU air relief trenches)
- Eight Orenco carbon filters (for ATU air relief system)
- Complete control and alarm panel, American Manufacturing Company Inc., Gainsville, Va.
Tony Birrittieri of Petersen Supply looks over a blower for one of the Bio-Microbics FAST treatment units his company supplied for the project.
Foreground, two FAST treatment units. Background, the project’s three flow equalization, recirculation, and FAST system dosing tanks.
The system was designed for simplicity of operation and service. For example, all pumps are identical so that only one type needs to be maintained and only one type of replacement stocked; all pumps are rail-mounted for ease of maintenance access.
A crane lowers the upper section of a FAST system tank.
Wastewater from the complex is pumped through a 4-inch force main to the two 18,000-gallon trash tanks, which provide settling. Water then flows by gravity through a 4-inch pipe to the three bottom-connected 18,000-gallon surge/recirculation tanks. Two pumping stations in the flow equalization/surge tanks dose the FAST units at 312.50 gallons per dose, 24 doses a day.
The FAST (fixed activated sludge treatment) process uses a combination of attached and suspended growth organisms in an aerobic, packed-bed bioreactor. This combination provides the stability of submerged, fixed-film media and the effectiveness of activated sludge treatment.
An above-ground blower, the system’s only moving part, introduces air to the treatment module to facilitate circulation of wastewater through the media’s channeled flow path. Fixed-film media provide a high surface-to-volume ratio to maintain microbe growth during low, average and peak usage. The system produces clear, odorless effluent that’s ready for drainfield distribution. Effluent condition at the Northernaire is 30 mg/l BOD and 30 mg/l TSS.
At times of low flow (generally at less than 30,000 gpd), some effluent flows back to the recirculation tanks by way of a recirculation ball valve. “This enhances treatment and helps sustain robust microbe populations in the system,” observes David LaBott, designer and soil scientist with Baudhuin Inc. At flows above 30,000 gpd, the recirculation ball valve seats, recirculation stops, and all FAST effluent is routed toward the drainfields.
Water destined for the drainfields enters the first of three compartments in the 6,000-gallon splitter/ effluent pump tank. It passes through the effluent filters into the second compartment (stilling tank), and then into the third compartment, where a splitter device divides the flow for the drainfield cells.
Effluent leaving the splitter tank flows to lift stations, from which it is pumped to the drainfield dose tanks. Effluent is demand-dosed to the drainfields at 3.5 feet of head. The drainfields include a west cell with 24 trenches 100 feet long and an east cell with 24 trenches 200 feet long.
The control panel from American Manufacturing regulates dosing and all other system functions. Its alarm system includes automatic remote dial-out to the service provider in case of anomalies.
A key component of the installation is an odor-control system. Air vented from the four ATU tanks passes through a pair of air relief trenches, consisting of drainfield chambers backfilled with an uncompacted mix of loamy sand and sand. Air escaping from the trenches is effectively deodorized by the soil and the use of carbon filters.
The entire installation took three weeks during August 2006. “It’s absolutely critical for systems of this kind to be installed correctly,” says Steve Bergeman. “For one thing, in a project like this with expensive condominiums on the lake, you want to make sure that there will be no odors in the future.”
A crew from Bergeman Plumbing & Heating first installed the tanks, A crane lowers the upper section of a FAST system tank.