The objectives of this study were to monitor and evaluate the nutrient, crop, and hydrologic parameters affecting the Thayne, Wyoming, wastewater treatment system. Cheeseplant wastewater and municipal sewage were mixed, pretreated, and applied to a 15 hectare sprayfield on a year-round basis. An ice pack formed during November or December, depending on weather conditions, and lasted through the middle of April. Samples of groundwater and water from adjacent springs have shown that after three consecutive years (1975-77) of spraying wastewater on the field and with a build-up of the ice pack each winter, no significant amounts of pollutants have reached the groundwater. Organic nitrogen was oxidized as it traveled through the ice pack and upper part of the soil mantle during the winter. Reduction of BOD5, COD, and nitrogen forms to migrate in the ice pack was observed, clearly showing the concentration of these parameters at the surface and bottom of the ice pack. Garrison creeping foxtail appeared to be most adapted to the sprayfield of those species tested. Reed canarygrass, smooth bromegrass, and western wheatgrass were also able to survive the harsh environment of the sprayfield. The forages studied could, at specific stages of growth, contain sufficient NO3-N to be toxic to livestock.

Issued July 1978. Includes bibliographical references (pages 63-65). Prepared by University of Wyoming under Grant no. Contract Number: R803571.