Jeffrey Hanson grew up on the shores of Birch Lake north of Babbitt, MN, the birthplace of taconite mining. He and his brother helped their dad build a house facing Finn Bay, a sight Jeff always found inspiring. His mother, an early advocate for natural foods, gardened among the rocks and raised four children in the woods. Jeff learned to cherish the natural environment around him. Although Reserve Mining had built Babbitt and the high school where his father taught industrial arts, Jeff didn’t think much about mining since the pits were hidden behind the hill.
Then in the mid-60s, sulfide ore deposits were discovered near the Kawishiwi River that flows into Birch Lake. In the mid-70s the news reached Jeff that sulfide ores lying over the taconite deposits at the Dunka Pit of Erie/LTV Mining were carrying acidic runoff and dissolved metals into Birch Lake. In 1973 Minnesota established a sulfate standard to protect wild rice, but Jeff learned that it was rarely enforced because no one knew a good way to remove sulfate from the water. He became concerned about possible negative impacts of mining on Birch Lake and the watershed downstream. Thirty years later Erie/LTV Mining ceased operations, but even then, Jeff knew, the Dunka Pit continued to drain into Birch Lake. He learned that the mine pits at Erie/LTV had become mine pit lakes with increasing levels of dissolved sulfate.
Shortly after returning to Minnesota from Brazil in 2005, Jeff began working with plastics recycling to divert this waste stream from landfills. One of the creative uses for recycled plastic that Jeff envisioned was for artificial floating island wetlands. In floating treatment wetlands, plastic fibers can economically provide a huge surface area where microbes can attach, grow, and clean water naturally.
In 2010 a bioremediation engineer, Mark Riensel, from Montana pointed out that the anaerobic environment under an artificial floating island wetland provides ideal conditions for sulfate reducing bacteria (SRB). There the SRB reduce sulfate to hydrogen sulfide much as they do in bogs and swamps. Jeff recognized that, if he could harness these SRB to grow on the enormous surface area of the recycled fibers and get them to reduce the sulfate in a controlled way, he could remove the resulting hydrogen sulfide and biologically get rid of sulfate in mining-impacted waters. He was inspired - could he really mimic nature’s process within a mine pit lake before the sulfate is discharged downstream?
Jeff, with his associate Rob Scarlett, directed the work of his company, Clearwater Layline, to exploring sulfate removal. In 2011, bench scale tests confirmed that the proliferation of SRB could be encouraged in a controlled system and that they would convert sulfate to hydrogen sulfide, which could then be treated with iron to form an insoluble precipitate.
The modular bioreactor design developed by Clearwater Layline for full scale field testing consists of a bioreactor module 7 foot square on the top deck that floats about 8 inches above the surface of the lake and extends 12 feet down into the water to provide a 4,000 gallon controlled containment vessel. This module has a defined inlet and outlet that allow for continual performance measurements on the outlet and defined amendments added to the water at the inlet to effectively manage performance. Inside each bioreactor module are non-biodegradable, recycled fibers that provide the surface area equivalent to 2 football fields for bacteria to attach to. This fact combined with a 90% void volume of the fiber mass provides 50 to 100 times higher performance potential then other bioreactors with inorganic attachment media.
Conceptual Drawing of 2 Rafts, Each with 8 Bioreactor ModulesWith this design concept in hand Clearwater Layline obtained funding in 2012 from the Laurentian Partnership of the Iron Range Resource and Rehabilitation Board (IRRRB) and the Natural Resource Research Institute (NRRI) of the University of Minnesota to initiate field tests of the modular Floating Sulfate Reducing Bioreactor concept. Cliffs Natural Resources and PolyMet Mining agreed to let the company use a mine pit lake in Area 5 of the old Erie/LTV mine site. In early spring of 2013, Clearwater Layline launched the first four bioreactor modules into the mine pit lake, which had a concentration of about 1,100 mg/L of sulfate. By July the units had proven their success.
In 2014 fourteen new bioreactor modules were deployed for year around operation as Phase II of the field tests, funded by IRRRB and NRRI. The data quickly confirmed effective wintertime operation and excellent sulfate reduction. NRRI and the University of Minnesota recognized that Clearwater Layline’s project could be a platform for gaining a better understanding of the sulfate-reduction process.
Operating Bioreactor Raft the Winter of 2013 to 2014Even when it’s forty below zero and the frozen mine pit lake looks life-less, there under the ice and snow trillions of bacteria are hard at work. Their home is a web of tiny plastic recycled fibers. And they are happily hard at work converting sulfate to sulfide.
Bioreactor Rafts A & B Operating the Summer of 2014
In early 2018, Clearwater Layline worked with RNAS Remediation Products to define new electron donor and nutrient feed possibilities that will significantly reduce the operating costs of the biological part of the system.
The company then incorporated USP Technologies’ proven PRI-SC method of converting hydrogen sulfide to elemental sulfur and ferric hydroxide. The technology produces a sludge that can be totally removed from the water to avoid any possible recreation of sulfate or sulfide.
A new company, Clearwater BioLogic, LLC, was then formed between Jeffrey Hanson of Clearwater Layline LLC and Bill Newman of RNAS Remediation Products Inc. to install and operate sulfate reduction systems based on this combined technology. The huge surface area of ClearwaterBioLogic's recycled fibers with 7,000 m2/m3 and 90% void volume provide enormous economic and performance advantages over existing biological systems.