Vegetative Filter Treatment of Dairy Milkhouse Wastewater

A vegetated filter strip constructed to treat milkhouse wastewater from a Vermont dairy farm was evaluated to determine its effectiveness in reducing solids, P and N concentrations and exports in surface and subsurface flow. The liquid waste was applied twice daily via a level lip spreader at a rate of 2.94 cm/wk on a vegetated loam soil having a 2% slope. The flow and concentrations of inputs and surface and subsurface outputs were continuously monitored during the 2-yr study. The strip significantly (P < 0.01) reduced solids, P, and N on a concentration basis, and retained 95% solids, 89% P, and 92% N on a mass basis. Retention was the greatest during the growing season and the poorest during snowmelt periods. Concentrations in subsurface outputs were greater than in surface runoff and over 75% of the mass export was in subsurface flow. Comparisons of this study with values reported in the literature suggests that hydraulic loading rate governs the effectiveness of filter strip treatment. Contribution from the School of Natural Resources, Univ of Vermont. Funding provided by USDA-SCS.