The owner of a concrete block fishing cabin on the Rio Pueblo River near Sipapu, N.M., wanted to remodel it and build a 3,000-square-foot, three-bedroom year-round home. The 1950s cesspool, however, was unacceptable.
Michael Montoya of the state Environment Department struggled to find an onsite solution. His only option was a holding tank, which the onsite regulatory code did not allow. He called around and was directed to Link Summers, president of Link Summers LLC in Taos.
“I had to meet 50-foot setbacks from the wells and river,” says Summers. “The property had one little triangular space that met those requirements, but wasn’t large enough for a typical advanced treatment system with drainfield.”
His non-discharging solution includes advanced oxidation, solar evaporation, chlorination, irrigation, and splitting of the black and graywater flows. The system can recapture and reuse treated water, although that capability has not been activated.
Site conditions
The flat, 100- by 125-foot lot extends to the river. The property, at 7,000 feet above sea level, has a mountain behind it. Soils are silty loam and rocks (riverbed) with 2-square-feet-per-gallon absorption area. The water table is four feet below grade.
System components
The blackwater system is sized for 60 gpd; the graywater for 315 gpd, equaling 375 gpd. The major components are:
Blackwater
• 1,000-gallon rotationally molded polyethylene two-compartment septic tank. All tanks made by AK Industries, Plymouth, Ind.
• 300-gallon round treatment tank.
• UltraViox advanced oxidation system from UltraViox LLC, Taos.
• 30-gallon pump basin.
• 1/3-hp Grundfos effluent pump.
• 7,000-gallon solar evaporation bed, Link Summers LLC, Taos, N.M.
• 1,500-gallon overflow tank.
• Audio and visual high water alarm, SJE-Rhombus, Detroit Lakes, Minn.
• Telecommunication system, Link Summers LLC.
Graywater
• 300-gallon pump tank with chlorine tablet disinfection.
• 1/3-hp Grundfos pump
• Subsurface drip irrigation line
• Two EZflow geosynthetic aggregate drainage tubes, Ring Industrial Group, Oakland, Tenn.
Blackwater system operation
From the house, blackwater flows through a 4-inch PVC pipe to the septic tank. The second compartment is aerated to start biological activity. Effluent gravity flows to the treatment tank, where the advanced oxidation system consumes remaining solids. “The unit combines ozone and UV light to create a physical chemical reaction similar to igniting a blowtorch underwater,” says Summers, who invented the system.
Clean water gravity flows to the pump basin, which doses the solar evaporation bed on demand. An overflow tank eliminates discharge. Temperatures inside the bed reach 180 degrees or higher. At an altitude of 7,000 feet, such temperatures are close to boiling, producing a high rate of evaporation.
A 4-inch duct fan operated by a dual-control temperature and humidity switch exhausts water vapor into the air during warm months or into the ground through a drain pipe in winter. “The Environment Department considers the evaporation bed to be a solar still, meaning the condensate produced from the water vapor is distilled,” says Summers. “We can do what we want with that water, including recovering it for any use.”
The bed’s black liners absorb heat, and eutectic salts — roughly 10 times more efficient at holding heat than water — store some of it. “Eutectic salts shift from a solid to a liquid and back again in the bed’s temperature range, enabling us to store a lot more heat with a lot less volume,” says Summers. “At night, they prevent the bed from cooling by releasing the heat created as the salts shift from a liquid to solid state.”
On cloudy days, water can be stored in the evaporation bed, which has a 116-day capacity. The overflow tank, a redundancy feature, plugs into the septic tank to continue running water through the loop.
Graywater system
Water gravity flows through a 3-inch PVC pipe to the pump tank with chlorine tablet disinfection. During warm months, the water is pumped to a subsurface drip line for irrigation. When the water isn’t used for irrigation or during winter, it gravity flows to the 40- by 8-foot drainfield.
The Environment Department tested graywater and proved that it contained no BOD or nitrogen, the principal contaminant of concern. Consequently, the state passed a graywater bill allowing subsurface discharge if the liquid is pathogen-free. “Disinfection is easy, but we’re still required to test quarterly for pathogens,” says Summers.
System installation
The only unknown was the height of the sun on the shortest day of the year. It remained slightly above the top of the mountain, ensuring that the evaporation bed had solar exposure. The first earthly obstacle was the architectural plan specifying a two-story house. “It would block sunlight to the evaporation bed, so the structure was lowered to one story,” says Summers.
The second obstacle was the boulders and every size rock in between that thwarted the backhoe’s progress. “Excavation was the hardest part of the project,” says Summers. “We pulled out two tandem loads of boulders.”
The cesspool was pumped, disinfected, collapsed, and partially removed to make room for the septic tank. Building the 16-foot-square by 4-foot-deep solar evaporation bed was the second hardest part of the installation. After excavating the hole, the crew sank the 6-inch-thick expanded polystyrene foam forms into the ground and filled them with concrete. “The foam has an insulation factor that stops cold transferring into the tank from the outside,” says Summers.
Six inches of prewashed sand created the bottom of the bed, followed by the first 20-mil black plastic liner. Two perforated 2-inch PVC pipes equally spaced lay on top of it. They run with a slight slope to viewing ports. “We should not see water in them,” says Summers. “If we do, we have a leak.”
A second 20-mil liner covers the pipes. Penetrations in the liners for the influent line from the pump basin, viewing ports, and outlet line to the overflow tank are sealed and clamped. The tops of the liners are secured beneath an aluminum L-channel lag-bolted to the concrete frame.
Covering the bed is an assembly of triple-wall Lexan attached to a 1-inch-square aluminum frame that drops into the L-channel. “We used triple wall because it adds insulation value,” Summers explains. Because the graywater effluent was treated, the state code allowed Summers to reduce the size of the disposal field. His crew dug two 1-foot-wide trenches on 6-foot centers for the 40-foot-long drainage system. They buried the tubes four feet deep.
Maintenance
The manufacturer requires a maintenance contract for the life of the system. Environmental Monitoring and Testing in Taos checks the system quarterly to make sure the UltraViox, pumps, and duct fan are running. The firm also samples the graywater for fecal coliforms. “Advanced oxidation produces more inorganic solids than organic solids, so the septic tank will probably need a pump-out every two years,” says Summers. “We really don’t know yet. It depends what the occupants put into the tank.”
Summers’ non-discharging system enabled the homeowner to build his year-round house and triple his property value.
