For more than a century, cheesemakers and vegetable processors have applied water remaining after production to open fields and farmland. The wastewater was used to wash vegetables, or contains whey left over after milk was processed into cheese. Over the years, producers have removed most impurities from this wastewater. But there was no definitive answer on whether the remaining nitrogen (in the form of nitrate) was polluting groundwater and residential water wells.
The report of a 3-year study, jointly funded by industry and the Wis. Department of Natural Resources, was recently released. The results offer some support for the long-held belief that much of the nitrogen in the wastewater leaves the soil and harmlessly enters the atmosphere.
The groundbreaking study also showed that rates of this process, called denitrification, vary depending on season, soil type, crop cover, and application rates. Because the atmosphere contains about 78% nitrogen, measuring transfers from the soil is extremely difficult, says study leader Francisco Arriaga, an assistant professor of soil science. The automated technology developed in his lab captures and measures nitrogen as it escapes to the atmosphere; efforts by PhD candidate Clay Vanderleest were instrumental in developing this technology for the study.
For more on this report, go to https://news.wisc.edu/food-processors-uw-collaborate-to-remove-guesswork-from-wastewater-disposal/