Field testing, phase 2

In 2014 fourteen new bioreactor modules were deployed for year-round operation as Phase 2 of the field tests, again 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.

The system operates reliably year-round.

Progress was boosted further in 2015 by a grant from MnDRIVE, a partnership between the University of Minnesota and the State of Minnesota that aligns research with industry needs to address “grand challenges.” The grant enabled NRRI and Clearwater Layline to build an additional bioreactor raft of seven modules, along with the previous fourteen, and provide research data for NRRI, UMD, and the University of Minnesota through late fall 2016. In July 2017, the results and conclusions were published as The MnDRIVE Interdisciplinary Project Implementation of Smart Remediation Technologies to Reduce Sulfate in Northeast Minnesota Watersheds.

The report confirms that

• The modular system successfully operated year-round for over 4 years.
• From beginning sulfate concentrations of about 1,100 mg per liter, the system regularly achieved 90% + sulfate reduction to hydrogen sulfide.
• The system provided up to 100% sulfate removal, even in winter.
• Sulfur was removed as FeS and elemental S precipitates.

Even after the publication of the MnDRIVE report, Clearwater Layline continued analyzing the data and reviewing operational records. The company found ways to improve the system throughput, stabilize performance, and significantly reduce capital costs.