Setting Up Camp

Tough winter weather and a requirement to handle waste from 220 oilfield workers challenges the designer and installer of a Montana onsite system.
Setting Up Camp
Justin Buchanan of E-On Northwest in Bozeman, Mont., empties MetaRocks into the treatment chamber of an Eliminite fixed-film bioreactor. (Photos Courtesy of Eliminite, Belgrade, Mont.)

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An oil support services company decided to build a camp for 220 workers outside Fairview, Mont., to serve oil production in the Bakken region. Officials hired Travis West, RS/REHS, of Engineering West in Columbus to design the onsite system and related infrastructure.

Winter temperatures along the Montana-North Dakota border often hover in the single digits and can fall to -40 degrees F. To handle the cold and its effect on the biological treatment process, West specified the pre-engineered fixed-film bioreactor system invented by Thomas Kallenbach, P.E., of Eliminite in Belgrade, Mont., and Justin Buchanan, owner of E-On Northwest in Bozeman, Mont.

“These units have a proven track record for high-quality effluent in sub-zero temperatures,” says West. “They’re reliable and don’t require a wastewater treatment operator to maintain them. They also enabled us to reduce the drainfields’ footprints by 50 percent, which was major in conserving space for the mandatory replacement drainfields.” West used Squirt, a patented computer software program, to analyze drainfield hydraulics and determine pump criteria.

The technology achieved aerobic nitrification, anaerobic denitrification, solids settling, and BOD reduction in a unified process. The pressure-dosed system, which went online in March, met the worker camp’s tight startup deadline and is functioning properly.

Site conditions

Soils are clay loam with a percolation rate of 32 minutes per inch and a loading rate of 0.3 gpd per square foot.

System components

West designed four independent systems to treat a total of 10,000 gpd. Components are standardized for ease of replacement and stocking spares. Each 2,500-gpd treatment train has:

  • Three 2,500-gallon dual-compartment concrete septic tanks made by Three Forks Concrete, Three Forks, Mont.
  • A100-8 effluent filters (Polylok)
  • Eliminite 620C bioreactor with integral pump chamber in concrete tank. Tanks made by Flathead Concrete Products, Kalispell, Mont.
  • Duplex 1 hp SHEF 100 discharge pumps, Hydromatic, Pentair Pump Group
  • 1 hp Hydromatic SKHS 100 recirculation pump
  • 500 feet of 1.5-inch pressurized pipe inside standard 36-inch BioDiffuser chambers from Advanced Drainage Systems
  • Control panel from SJE-Rhombus

System operation

The camp is divided into quadrants, each with its own onsite system. Wastewater gravity-flows through 4-inch PVC laterals to the septic tanks set in line, then into the treatment unit. The recirculation pump doses the attached growth media on a programmed schedule. When activated, the pump sends effluent into a spray bar that evenly distributes it through three heads over 500 cubic feet of MetaRocks.

MetaRocks are spheres of closed-cell polyurethane resins with three deep contoured channels that provide large, open pores for passive air transfer. A coating of coarse sand and finely crushed recycled glass enables a thin liquid film to cover the entire surface and promote even, consistent bacterial growth.

The 7-foot-deep packed media bed needs no cleaning or replacement. Nitrified liquid collects at the bottom of the tank. Each time the recirculating pump engages to dose the media, it returns a portion of the fluid through the denitrification line to the first septic tank.

The Lung, a proprietary air entrainment device driven by the recirculation pump, supplies oxygen to the microorganisms. Whenever the recirculation pump runs, it discharges air drawn into the Lung from the previous cycle into the bioreactor. When the pump shuts off, liquid drains by gravity back to the pump chamber, simultaneously drawing air into the Lung.

As wastewater enters the unit, the rising liquid engages the alternating float-activated discharge pumps in the pump chamber. “On-demand dosing doesn’t require a separate dose tank and it reduces the system’s complexity, and makes it far more predictable and reliable,” says Kallenbach. “It’s important that these systems run themselves.”

Each discharge pump sends 300 gallons through a separate 2-inch 160 psi DR 11 HDPE Schedule 40 force main to its dedicated half of the drainfield. “The only thing between the pump and drainfield is pipe,” says Kallenbach. “That gives the system true redundancy, and nothing mechanical to break down.”

Each section of drainfield has 1.5-inch pressurized pipe suspended with plastic snap-tie fasteners inside five 100-foot-long laterals on 7-foot centers. The 1/8-inch orifices on 5-foot centers spray up at 8 to 10 feet. “Based on similar systems serving the Montana highway rest areas, we’re seeing CBOD, TSS and total Kjeldahl nitrogen removal in the 99 percent range,” says Kallenbach. “Without using chemical additives, we’re also seeing total nitrogen removal in the 90 percent range, and these numbers are from winter samples.”

Installation

The week before Buchanan arrived at the camp, the project manager reported subzero temperatures with -60 degrees F wind chills. Buchanan packed a 13- by 20-foot wall tent to pitch over the excavations, a propane heater and survival clothing. He also shipped two semi-truck loads of MetaRocks 500 miles to the site.

Masco Construction Co. of Moses Lake, Wash., dug excavations for the tanks, set them, and installed the drainfield and camp infrastructure. Mild weather arrived the first week of February, making the wall tent unnecessary. It also thawed the soil late in the day, producing a challenging, sticky mud that clung to boots.

Daytime temperatures ranged from the teens to the thirties with little wind. “The days were sunny and pleasant, but we still had to bundle up,” says Buchanan. Bulky clothing made moving more difficult and added time to every operation.

To keep the microorganisms warm, Buchanan lined the tanks and lids with 2-inch-thick polystyrene (subgrade) insulation. The lids and risers were designed to reduce surface exposure. “Open a large hatch riser on a subzero day and the heat loss will cool the whole system,” says Kallenbach. “Using 24-inch risers on these tanks restricts heat loss.”

Buchanan and Masco coordinated their efforts to install the media. Using the excavator arm, the Masco operator suspended two bags of MetaRocks at a time over a treatment unit, then Buchanan pulled the chute on the bottom of the bags to release the flowable media. It took nine bags to fill a treatment chamber, then the operator set the lid. Buchanan plumbed and wired the unit while Masco workers installed the drainfields.

After setting floats and mounting control panels, Buchanan used a generator to connect and test the panels. The installations took six days. Meanwhile, Masco pumped trucked-in water from one septic tank to the next to leak-test them. They also transported 1,500 gallons to each bioreactor for testing, then Masco covered them with 2 feet of soil. They buried the septic tanks to the same depth and mounded soil around them.

Maintenance

E-On Northwest has the maintenance contract. Buchanan provided a site-specific maintenance manual with photographs and site plans showing where components were installed. The state Department of Environmental Quality requires effluent testing twice per year for the first two years, then annually.



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