Fort Sheridan Project Description

USEPA Region 7 contracted KEMRON to identify and development an optimum treatment program as part of the removal actions for the Ten Mile and Basin drainages located in Lewis and Clark County, Montana. USEPA Region 7 has established a regional repository for storage of waste rock, mine tailings and impacted soils . The repository produces leachate over the summer months about one million gallons. This leachate is characterized by a low pH (less than 3.0 s.u.), high sulfates (up to 2,000 mg/l) and heavy metals in relatively high concentrations.

Initially, a land application disposal (LAD) area was identified for management of the site leachates. LAD was identified based on anticipated sulfates and metal concentrations in the site leachate. The treatment goals for application of the leachate to the LAD were sulfates below 250 mg/l, arsenic less than 4 mg/l, zinc less than 25 mg/l, and lead less than 25 mg/l. However, on-going analysis revealed that actual site leachate concentrations were well about acceptable levels for land application. Samples collected in the spring from the leachate showed levels of sulfate concentrations at 2,750 mg/l and zinc 318 mg/l. As such, treatment of the repository leachate was identified as necessary prior to land application.

In an effort to identified an optimum treatment program, KEMRON evaluated a wide range of standard and innovative treatment technologies. Parameters utilized to identify appropriate technologies included 1) ability to reduce sulfates and metals concentrations, 2) ability to adjust the final pH, 3) capital equipment costs, 4) operations and maintenance costs, 5) labor requirements, and 6) site-specific criteria.

Project Facts

Client	USEPA
Value	$230,000
Location	Lewis and Clark County, Montana

Relevant KEMRON Service Areas:

Bench Scale Testing

Pilot Scale Testing

Water Treatment

Chemical Treatment

System Installation

System Optimization

Operation and Maintenance

Included in this program were literature searches, past experience of treatment specialists and bench/pilot treatability studies conducted on leachate from the repository.

Eventually, a two-stage treatment system was identified based on this technology review. The system was composed of an initial reverse osmosis (RO) treatment followed by chemical precipitation. Reverse osmosis was identified due to its ability to reduce both metals and sulfates from the water. Chemical precipitation was utilized primarily to treat concentrate resulting from RO treatment. The two, in conjunction, were then utilized prior to ultimate placement in the LAD area.

A review of available options resulted in the identification of used equipment which was then utilized at the site. Used equipment was utilized due to 1) the tight schedule which did not permit the fabrication of new equipment, and 2) cost issues. Used equipment was then mobilized to the site and the water treatment system was completed in the spring of 2001.

Due to the restrictions in budget, site layout and anticipated length of the project, used equipment was evaluated and utilized from the site. There is an abundance of used water waste treatment equipment in the market due to the varied in the computer business. Most computer manufacture produces need very clean water for manufacturing process. When production is changed or closed this equipment is available at greatly reduced costs. This used equipment is about 20-50% of the cost of new equipment.

Through the first season of operation, the system treated and discharged over 800,000 gallons of contaminated leachate at the site. Treatment at the site exceeded expectations, with all water discharged to the LAD well below the discharge criteria. In fact, most criteria were several orders of magnitude below acceptable levels. In addition, costs were minimized and resulted in a current rate per gallon of well below previous treatment systems used at the site. Costs are expected to decrease even further over future years.