From June to July, 2013, a team of scientists working under the auspices of IHSS began the challenging task of isolating NOM from the Mississippi River in Minneapolis, Minnesota, USA. The team included E. Michael Perdue (former IHSS President), Nelson W. Green, and Shamus J. Driver from Ball State University. They were assisted by other scientists, including Rachel Williams from Louisiana State University, Fernando Rosario-Ortiz from University of Colorado-Boulder, Sabine Dvorski and Norbert Hertkorn from Helmholtz Zentrum München, and by Paul Bloom from the University of Minnesota. Funding was from the IHSS and the US Environmental Protection Agency (USEPA).
Initial Setup of the Field Laboratory. The IHSS team set up the field laboratory from June 3rd through June 13th, 2013. The major components of the lab included a six-channel filtration system, five RealSoft PROS/2S RO systems and a 200-liter sample processing tank, a reverse osmosis/electrodialysis (RO/ED) system, additional RO systems for production of clean RO permeate water that was used for rinses, cleaning, preparation of reagents, etc. Plumbers and electricians from the Minneapolis Water Works provided substantial assistance in setting up a functional and safe laboratory for this project. RealSoft PROS/2S RO systems were loaned to IHSS by Patricia Maurice (University of Notre Dame), Robert Cook (Louisiana State University), Louis Kaplan (Stroud Water Research Center), and Jane Ellen Simmons (US EPA, Research Triangle Park, NC).
Overview of the Sample Collecting Field Trip. Processing of water from the Upper Mississippi River started on June 13th and continued on a daily basis through July 14th. RO/ED processing started on June 15th and continued through July 15th. Altogether, 140,060 liters of Upper Mississippi River water were filtered sequentially through 1.0 µm and 0.45 µm filters, processed by RO to obtain 2505 liters of RO concentrate (a water concentration factor of 55.9), and then processed by RO/ED to obtain 1,160 liters of RO/ED concentrate (a water concentration factor of 2.16). The overall water concentration factor was 120.8. Conductivity increased from 290±30 µS/cm in the filtered raw water to 14,100±3,900 µS/cm during the RO process. Conductivity was then decreased to 4,600±1,200 µS/cm during the RO/ED process.
Final Processing. The concentrated sample was taken to Ball State University for final desalting and preparation for freeze-drying. Freeze-drying was conducted at a commercial food processing facility in Momence, Illinois. The IHSS received 1250 g of NOM, with most of the remainder of the NOM delivered to USEPA. Small aliquots of NOM were provided to the research groups who participated in the work, either by loan of equipment or by direct participation.