Healthy Alternative

Peat biofilters and a UV disinfection system enable replacement of a mobile home’s onsite system discharging directly to a creek
Healthy Alternative
Timothy Davis uses a Kubota U45 tracked mini-excavator to dig holes for the tanks in the small space between the home, property line and creek.(Photos courtesy of Appalachian Photography)

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For 12 months or longer, sewage ponded under a three-bedroom mobile home in Alkol, W.Va., until it spread 30 feet beyond the skirting. The low-income family qualified for a replacement system through a project of the Lincoln County Commission and state Department of Environmental Protection (DEP).

“Our goal is to protect public health and water quality by preventing E. coli from contaminating the Left Fork Watershed of the Mud River,” says Ric MacDowell, project lead investigator of the Lincoln County Commission Green Wastewater Projects in Hamlin. “We set a benchmark of no more than 200 E. coli colonies per 100 ml.”

The project required alternative systems to be NSF 40 Certified and approved by the DEP and the Department of Health and Human Resources. Puraflo peat fiber biofilters from Anua, formerly Bord na Mona, met the qualifications, producing effluent averaging less than 10 mg/l TSS and BOD and 99 percent fecal coliform reduction with no pathogens.

“This system also required UV disinfection for direct discharge, necessitating an NPDES permit from the DEP,” says MacDowell. Timothy Davis, owner of TR Davis in Branchland, won the bid.

“Of all the jobs, this home was the most dreaded,” he says. Besides the health hazard, he faced cold, snow and limited space. After the system went into operation, direct-discharge effluent samples had less than 10 E. coli colonies per 100 ml.

 

Site conditions

Soils, which failed a percolation test, are sandy to sandy loam with the water table three feet below grade. The 0.75-acre lot is on a slight hill 100 yards from Flat Creek.

 

System components

Based on state code requiring one module per bedroom, Davis sized the system for 450 gpd. Major components are:

1,000-gallon dual-compartment TW-Series polypropylene septic tank with A300 Zabel effluent filter (Polylok). Tanks made by Infiltrator Systems.

1,000-gallon single-compartment polypropylene dose tank with Champion 1/2 hp low-head pump and Infiltrator Systems transducer

Three 150 gpd Puraflo peat biofilter modules set in series

3G ultraviolet disinfection chamber from Salcor

Aquaworx IPC control panel from Infiltrator Systems

 

System operation

The septic and dose tanks are set in series. After wastewater gravity-flows into the dose tank, the transducer compares the air pressure in the bell to the air pressure in the tank to determine the liquid level, cycling the pump about every two hours.

In 60 seconds, it pumps 36 gallons through a 2-inch Schedule 40 PVC force main to a manifold that sends 12 gallons to each module. A distribution grid at the top of the units evenly doses the peat.

Purification occurs as the liquid percolates through the media over 36 to 48 hours. The peat also suppresses odors. Effluent from the modules gravity-feeds through 2-inch PVC pipe to the UV chamber.

Water flows down and around the UV lamp in a Teflon antifouling sleeve, making a semicircle before discharging through 25 feet of 4-inch PVC pipe buried 18 inches deep. The outfall is into Flat Creek, which is part of the Left Fork Watershed.

 

Installation

Davis visited the property to decide where to install the components, then submitted his design to the DEP for approval. “We had limited space between the home, property line, and creek, and there was an underground telephone cable to avoid,” he says. “I saw no evidence of ponding around the existing drainfield, confirming our suspicion that effluent hadn’t reached it in a long time.”

While the crew crushed and filled in the old septic tank, Rick Frye, owner of Frye Septic in Spurlockville, pumped the sewage ponded in the northeast corner under the home. The area was allowed to dry as the crew broke through the frost barrier and dug holes for the tanks with a Kubota U45 tracked mini-excavator.

“There was a slight slope in front of the house that didn’t have a high water table, and that is where we installed the system,” says Davis. “The septic and dose tanks went in a 20- by 20-foot space, and the peat modules in a 10- by 30-foot space.”

Cold weather and snow returned as the workers set the tanks. They filled the septic and dose tanks half-full of water, plumbed them, and backfilled with native sand. The peat modules, each weighing 1,800 pounds, sat level on 6 inches of gravel.

Davis used a float tree bracket from SIM/TECH FILTER to mount the transducer. “Transducers are less labor intensive and easier to install than floats, and trash doesn’t hang up on them,” he says. The telemetry panel with pressure transducer technology allows real-time monitoring of the pump and liquid levels. It also relays alarms and enables Davis to troubleshoot the system. He mounted the control panel on the home.

Meanwhile, a worker entered the 3-foot-high crawl space under the home on hands and knees, unrolling plastic sheet before him. He saw that the 4-inch thin-wall lateral was disconnected from the toilet. The slope of the hill then directed the sewage to the northeast corner.

He replaced the entire lateral with 4-inch SDR35 PVC pipe and covered the ground with plastic to help subdue odors. “The installation was no piece of cake, but it was average for our area,” says Davis. MacDowell and Davis educated the residents on how to take care of the system.

 

Maintenance

The state requires direct-discharge systems to have perpetual maintenance agreements. The installer provides service for the first two years. Every six months, a technician opens the septic and pump tanks to check the scum, sludge and water levels, and cleans the effluent filter and UV lamp. The technician then runs a cycle on the pump, inspects the peat media for grease or ponding, looks for solids or particulate in the biofilter effluent, and checks the control panel and transducer.

The peat should last for 15 years or more, after which it will be vacuumed out and replaced. Davis expects to pump the septic tank every three to five years. MacDowell draws the direct-discharge effluent samples.



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