Filtering Water-Borne Sulfates and Heavy Metals through Biochar and Bacteria

  2017-18 Smith Partners Sustainability Fellow Gloria Thomas at the University of Minnesota

2017-18 Smith Partners Sustainability Fellow Gloria Thomas at the University of Minnesota

While legislators, state agencies, and environmental and mining advocates continue to debate the water quality impacts of mining, a team at the University of Minnesota is exploring whether a combination of biochar -- produced from biomass -- and sulfate-reducing bacteria can act as a filter to remove sulfate and toxic metals from mine water.

Gloria Thomas, 2017-18 Smith Partners Sustainability Fellow and PhD candidate in the Water Resources Science Program at the University of Minnesota, has joined a team of researchers at UMN who are in the lab phase of fine-tuning this bio-filtration technique.

Relatively inexpensive and using natural components, the biochar-bacteria remediation technique could be applied to reduce sulfate levels in water to protect wild rice and to meet Minnesota regulatory mandates.

A Bio-Based Remediation System

The two-component remediation system consists of biochar, biomass that is burned at high heat in a low oxygen environment to produce fine charred particles more porous and sorbent than charcoal, and bacteria that do not require oxygen and that take in and process sulfates.

In this low-cost, passive treatment system, biochar adsorbs heavy metals from the water, holding these metals on the surface of the biochar, while sulfate-reducing bacteria use sulfate to fuel their activity and convert the sulfate to sulfide. Sulfide then precipitates with metal ions into a solid that is less reactive in the environment than sulfide itself. Bacteria in waters with high sulfate concentrations naturally convert sulfate to sulfide, but elevated sulfide concentrations can be toxic to many life forms in the environment, including wild rice. The biochar-bacteria system circumvents this problem.

“Sulfide is harmful to animals and plants that breathe oxygen because it disrupts their metabolism,” explained Thomas. “Sulfide can cause irritation and inflammation of the respiratory systems and lead to lung edema if high concentrations are inhaled. Sulfide gas affects wild rice by preventing plants from taking up nutrients through their roots and inhibits the plants’ ability to take in oxygen.  If you walked into a marsh or field and noticed a pungent smell of rotten eggs, it would be from sulfide gas.”

Gloria Thomas2.jpg

Applications Beyond Sulfates

Thomas notes that field testing of the biochar and sulfate-reducing bacteria research is still to be conducted, and that future research is needed to make sure that the solid precipitate resulting from the heavy metal and sulfide gas combination does not negatively impact environmental systems. “Biochar is used already in bio-filtration systems to treat stormwater to remove nitrate, phosphate, and heavy metals,” noted Thomas. “Heavy metals can be removed by attaching to biochar. One study has shown that microbial pathogens, such as certain strains of E. coli, can be removed with the use of biochar filters.” 

The properties of biochar, such as high surface area and its porous structure, make biochar a good surface for microbial communities to grow on.

Biochar is an effective addition to bioremediation systems that contain various types of bacteria. Research is being done to study how biochar affects microbial community structure and activities, and how these communities can be used for applications such as wastewater treatment or other forms of bioremediation.

Thomas hopes her research will lead to a variety of remedial applications, and she is eager to contribute to broader public understanding of this work. "It would be very exciting if our research can help local communities and watersheds find cost-effective strategies to improve water quality," she noted. "This is perhaps one more tool at our disposal."

The Latest on White Bear Lake

  Image: MN Department of Natural Resources

Image: MN Department of Natural Resources

Both chambers of the Minnesota legislature have approved legislation that places a hold on new groundwater appropriation permit requirements imposed by the Minnesota Department of Natural Resources as a result of a Minnesota district court's 2017 order.

The legislation would prohibit the DNR from modifying permits or taking enforcement action based on the 2017 order, and would suspend the required changes for public water suppliers outlined in the order. Governor Dayton has said that he does not oppose the legislation.

The District Court's 2017 Findings and Order

In August 2017, the district court found the DNR to have committed violations of the Public Trust Doctrine and the Minnesota Environmental Rights Act through its permitting and management of high capacity groundwater appropriations around White Bear Lake and within the Prairie du Chien-Jordan aquifer. The district court's decision ordered the DNR to review all existing groundwater appropriation permits within a 5-mile radius of White Bear Lake within one year, and to require the permittees within that radius to submit contingency plans for conversion to surface water sources for their water supply.

The DNR's post-trail motions included arguments stating that the district court's ruling was not supported by the best science available and created precedent that could impose unnecessary burdens on Minnesota citizens.

2018 Proceedings

In January 2018, the DNR sought to stay the district court judgment, amend the judgment, and grant a new trial.

In March 2018, the district court issued an order responding to the DNR's January 2018 motions. The district court denied the request to amend its order and for a new trial. It stated that it applied the Public Trust Doctrine pursuant to existing law in finding that the DNR violated this doctrine by causing continual decline in aquifer levels and causing an adverse impact to lake size, and failing to remedy these impacts. The district court further stated that it did not create new law by applying state law retroactively to find that the DNR violated MERA by impairing White Bear Lake and the Prairie du Chien Aquifer.

The district court further denied the request for a stay of its 2017 order, stating that permit holders were on notice of the case and did not choose to join the litigation, and that the order of the district court provides sufficient detail for the DNR to carry out the permit review and other elements of the order in the face of potential legal challenges brought by permit holders. The district court concluded that the 2017 order would not have significant impacts on activities, including construction, within five miles of White Bear Lake, and that the DNR's history of failing to comply with state requirements would put at further risk the preservation of finite water resources should the district court issue a stay.

Employing Two-Stage Ditches to Tackle Water Quality and Soil Health

  Photo: Mower SCWD

Photo: Mower SCWD

If there is anything close to a silver bullet to yield a better bottom line for farmers while also improving water quality, it may be soil health.

As research continues, farmers, researchers, and watershed districts will likely have new opportunities to work together to improve soil health while helping reduce excess agricultural nutrients entering water systems.

Joe Magner, University of Minnesota researcher with the Department of Bioproducts and Biosystems Engineering, envisions opportunities for farmers to implement two-stage ditch technology that will improve water quality while benefiting soil health.

  Photo: Dan Mecklenburg, Ohio Department of Natural Resources, and Andy Ward, Ohio State University

Photo: Dan Mecklenburg, Ohio Department of Natural Resources, and Andy Ward, Ohio State University

Storing more water and improving quality

The two-stage ditch structure bio-mimics a natural stream, allowing for more water storage to take place within the ditch geometry than would naturally happen.

When water levels increase, water rises up out of the low flow channels and spills out over the benches, interacting with the soil and vegetation on the benches.

As fine sediment and nutrients carried by the water and within the sediment is trapped on the benches, the roots of plants—such as cattails—planted in the benches take up the nutrients through the water. 

At the end of a summer season, the cattails in the benches have absorbed phosphorus and other nutrients that can be re-applied to fields. Not only do the cattails provide nutrients to the soil, minimizing farmers' fertilizer costs, they contribute much-needed organic carbon to heavily utilized and intensively managed agricultural soil systems.

Magner notes that because Minnesota is so cold, cover crops can be challenging to grow. Harvesting cattails and putting them on the soil offers an alternative to planting cover crops for putting organic carbon back into the soil.

  Photo: BWSR

Photo: BWSR

Benefiting both soil and water health

Magner and fellow researchers have published papers about the two-stage ditch technology and water quality improvement tools, and have been learning from farmers in other states about the soil health benefits farmers are seeing when they focus on increasing organic carbon in their soils.

"How we measure and define soil health and biology could be one way to both help farmers stay afloat and improve environmental outcomes," notes Magner.

"The University of Minnesota is developing some tests and has some ideas about BMPs that are grassroots-driven, which is one of the most exciting things about this focus on soil health. In states like Indiana, the core of where focus on soil health improvements has taken place to date, the government is not creating incentives - farmers are choosing to improve the health of their soil and seeing results in input cost reductions (needing to buy less fertilizer) and, in some cases, experiencing higher yields."

  Photo: Ohio State University

Photo: Ohio State University

Magner gives the example of nitrogen fertilizer to describe the field - ditch connection important to the two-stage ditch treatment train he researches. Whether injected or placed on the soil surface, nitrogen fertilizer inevitably gets moved into what can be referred to as the soil nitrogen pool. Within the upper topsoil horizon, the soil incorporates nitrogen and phosphorus. If the topsoil is eroded, or if nitrogen or phosphorus is leached from the topsoil, it can end up in waterways.

The two-stage ditch provides a nutrient-trapping mechanism, in the form of cattail root and plant systems, located down-gradient of the farm fields. The trapped nutrients and organic carbon contained in the cattails can be re-applied to fields in the form of plant-matter fertilizer.

Investing now for long-term gain

Investing in building organic phosphorus application into production and increasing soil biological health shows little short-term profit. In the long term, however, benefits are at least two-fold.

  Photo: Gary Sands, University of Minnesota

Photo: Gary Sands, University of Minnesota

First, building soil organic carbon content supports healthier soil that requires less purchased fertilizer inputs. Second, cultivating and applying natural phosphorus sources can help farmers head off an anticipated shortage of that input.

Phosphorus for fertilizer use has been plentiful to date, but Magner warns of a time when that may no longer be the case.

"Within the next 25 years there will be a severe shortage of phosphorus fertilizer, and we will run out unless new mines are found," says Magner. "Putting an organic form of fertilizer that is both a phosphorus and organic carbon source back into the ground helps to build up the biological health of the soil."

Connecting with local government partners

Magner sees Minnesota's watershed districts as key members of creating partnerships around the state to help farmers improve the health of their soil. "Soil health is an issue everywhere in the state, and watershed districts are in one of the best positions to reach out and communicate about how to improve soil health and work together with communities to implement soil health BMPs."

Magner welcomes coordinating with interested watershed districts to determine if two-stage ditches are an appropriate tool for improving soil health in their area.

Modernizing Drainage System Maintenance

  Photo: BWSR

Photo: BWSR

For over a century, public drainage system maintenance and repair in Minnesota has been funded by assessing real property that drains to the system. Assessments are in the same proportion as the original assessment for construction, unless valuations have been updated through administrative procedures that often require extensive fieldwork and are expensive.

For several years, the Drainage Work Group (DWG), representing public and private groups with an interest in drainage matters and facilitated by the Chief Engineer, Minnesota Board of Water and Soil Resources, has worked to develop an alternative funding method.  In March, the DWG reached consensus on proposed revisions to the Minnesota Drainage Code (chapter 103E) to allow this method. The revisions are in legislation that has passed through Senate and House committees and appears likely to be enacted. Under the legislation, when a drainage system is to be repaired, the drainage authority may choose the traditional or the new method to assess cost.

The alternative, known as the “Runoff and Sediment Delivery Option” (RSDO), relies on Geographic Information System methods and new runoff and soil loss modeling capability to allocate drainage system maintenance cost on the basis of how much a tract of land contributes to that cost through accelerated runoff and contribution of sediment. In addition to being more equitable, proponents believe this will substantially reduce the time and cost to administer drainage systems. Also, where model inputs - and thus maintenance charges - can be adjusted easily on a tract basis to reflect changes in practices, the RSDO enhances the incentive for landowners to adopt improved practices.

BWSR Rejects Buffer Penalty Proposal

On April 2, the Board of Water and Soil Resources (BWSR) released for comment a proposed amendment to the Buffer Law Administrative Penalty Order to obtain feedback from local governments about the draft option to achieve buffer compliance. BWSR released a statement on April 9 updating the request for comments and noting that the BWSR Board plan adopted on June 28, 2017 had not been changed, and that the draft proposal on which BWSR was seeking comments attempted to respond to interest from the public regarding additional compliance options.

The proposed amendment outlined an alternative basis for measuring compliance, employing a one-time linear feet measure of compliance. The option was to be in addition to the approved Administrative Penalty Order Plan which determines compliance through a recurring fine on a per parcel basis. BWSR noted in its update that it did not plan to use the alternative basis for measuring compliance in those counties where BWSR has enforcement responsibilities under the Buffer Law.

On April 12 the BWSR Buffers, Soil and Drainage Committee passed a resolution to officially reject the draft amendment based on the comments received through the public notice, and BWSR will take no further action on the draft proposal.

Legislative Environment Chairs Introduce Pollutant Trading Bills

  Photo: MPCA

Photo: MPCA

Senate and House Environment Committee Chairs have introduced legislation to authorize the Minnesota Pollution Control Agency (MPCA), in collaboration with the Board of Water and Soil Resources (BWSR) to develop a watershed credit exchange program.

S.F. 2705 and H.F. 3120 outline a pollutant trading or banking program and make funding and MPCA fund management authority for such a program more explicit. Existing law authorizes MPCA to develop a trading program, and MPCA has overseen several point to point and point to non-point trades that have been reviewed on a case-by-case basis. The new bill could result in a streamlined program for generating, banking, and buying credits that is more widely used throughout the state.

While the bill does not include specific details about the "watershed credit exchange" program, one clear application is at public water treatment facilities located throughout greater Minnesota. Many communities are searching for funding for required public water treatment infrastructure improvements to enable them to meet water quality standards, especially for phosphorus.

  Photo: MPCA

Photo: MPCA

Some state funds are available through the Water Infrastructure Fund, but available funding does not enable all facilities to be funded through this mechanism.

A facility could purchase watershed credits to, at least temporarily, comply with water quality requirements for the facility. Watershed credits could be generated by non-point sources, for example, through best management practice (BMP) installation on farms resulting in quantifiable reductions of pollutants entering the water. A "credit bank" comprising multiple quantifiable reductions in water pollution would be available to enable public water treatment facilities to meet their water quality requirements at a cost lower than that of full-scale facility infrastructure updates.

Watershed districts could be key partners in the work of establishing and maintaining a bank of watershed credits for trading given their existing role in Best Management Practice development, water quality monitoring, and constituent engagement.

  Photo: BWSR

Photo: BWSR

Current Rulemaking

Municipal Water Fluoridation - Minnesota Department of Health

Groundwater Health Risk Limits - Minnesota Department of Health

NorthMet Permit - Department of Natural Resources

NorthMet CWA Section 401 Certification for USACE General Permits - Minnesota Pollution Control Agency

  • NorthMet 401 certification is now open, and the comment period runs through March 16, 2018.

Wild Rice & Sulfate - Minnesota Pollution Control Agency

  • In July 2017, MPCA proposed to change the rules related to the state's existing wild rice sulfate standard and wild rice waters.
  • Among other things, the rule proposed to change the current 10 mg/L rule to an equation-based water quality standard that accounts for a number of factors, including the amount of iron in a body of water. The rule also proposed to establish a new classification specific to wild rice waters (Class 4D), distinct from the current classification within the broader Class 4 Agricultural and Wildlife class.
  • On January 11, 2018, an Administrative Law Judge denied the MPCA's proposed rule changes.

Water Quality Standards and Tiered Aquatic Life Uses (TALU) - Minnesota Pollution Control Agency

  • MPCA's TALU framework amendments to state water quality standards, contained in Minnesota Rules Chs. 7050 and 7052, became effective on October 23, 2017.

3M Settles Lawsuit with MN Attorney General

The Minnesota Attorney General's Office and 3M agreed on a settlement amount of $850 million to settle a lawsuit filed in 2010 over industrial groundwater contamination. The Attorney General had sought at least $5 billion in damages from 3M for the company’s disposal of industrial chemicals -- including PFCs, which are bioaccumulative and harmful chemicals that can build up over decades and increase rates of cancer and birth defects -- in the Twin Cities Metro Area over the past 40 years. The $850 million will be provided to the state as a grant to fund clean drinking water and natural resource projects.

The settlement only covers damages to natural resources. The Attorney General's office stated that it has no jurisdiction to recover damages for personal injuries. 3M settled more than 3,500 personal injury suits last year, paying out more than $671 million.

Partnering for Water Quality and Flood Reduction Benefits

The Minnesota Department of Agriculture (MDA) announced a new collaboration among the MDA, Cedar River Watershed District, CFS Cooperative, Hormel Foods Corporation, Land O'Lakes SUSTAIN, the Environmental Initiative, and the Mower County Soil and Water Conservation District.

This public-private partnership, aimed at reducing flooding and improving water quality in the Cedar River watershed located in southeastern Minnesota, grew out of an agreement to enhance the state's water quality signed in 2016 by Governor Mark Dayton and Land O'Lakes.

  Photo: Minnesota Pollution Control Agency

Photo: Minnesota Pollution Control Agency

The partnership will engage CFS Cooperative, Land O'Lakes, and farmers located within the Cedar River Watershed to enable more precision agricultural practices and lead to farmers' participation in the voluntary Minnesota Agricultural Water Quality Certification Program, a 10-year guarantee of regulatory certainty in exchange for farmer-implemented conservation practices. Land O'Lakes and CFS help farmers become certified through direct education and technical assistance.