Publication Summary

Vadose zone sampling equipment was installed and sampled at two locations on the Tree Top land application site near Selah, Washington. Fruit processing wash water is applied at the site to irrigate pasture grass grazed by cattle. The purpose of the study was to evaluate wastewater treatment in the unsaturated zone and to test two devices for sampling soil pore water. Hollow glass bricks and barrel lysimeters were used to obtain water quality samples and to estimate water movement. Tensiometers tracked the movement of irrigation-induced wetting fronts. Chemical oxygen demand (COD), total nitrogen (total N), chloride, dissolved iron, conductivity, and total dissolved solids were sampled five times between June 26, 1992, and December 7, 1992.

Vadose zone sampling equipment was installed and sampled at two locations on the Tree Top land application site near Selah, Washington. Fruit processing wash water is applied at the site to irrigate pasture grass grazed by cattle. The purpose of the study was to evaluate wastewater treatment in the unsaturated zone and to test two devices for sampling soil pore water. Hollow glass bricks and barrel lysimeters were used to obtain water quality samples and to estimate water movement. Tensiometers tracked the movement of irrigation-induced wetting fronts. Chemical oxygen demand (COD), total nitrogen (total N), chloride, dissolved iron, conductivity, and total dissolved solids were sampled five times between June 26, 1992, and December 7, 1992.

Vadose zone monitoring showed that COD and total N were treated in the top 18 inches. The mean COD treatment was 85% (S.D.=3.8); that for total nitrogen 92% (S.D.=6.8). Biological oxygen demand (BOD5) was estimated from COD concentrations. Estimated BOD5 application rates were two-four times the monthly permit limits. Nitrogen application rates were two-five times higher than monthly permit limits. Barrel samplers worked better than brick samplers in the gravelly, sandy soils. Both samplers were difficult to install. However, all four barrels worked well, while only two of the twelve glass bricks yielded samples. COD concentrations in monitoring wells adjacent to lysimeters were less than half those in the lysimeters indicating dilution by ground water. Elevated chloride concentrations in some of the lysimeters and monitoring wells compared to the effluent indicate possible leaching of chloride previously accumulated in the soil.

Link to EIM data for User Study ID TREE TOP