Date of this Version
The Proceedings of the 4th International Symposium on Livestock Wastes (pp. 257-260)
Installation of a zero-discharge, runoff-control system is one method for solving potential water pollution problems from many feedlot operations. Even though the zero-discharge system is required by regulation in several states, this approach may be economically prohibitive for many small operations. An alternative is to install a vegetative filter system to adequately control the runoff so that violations of water quality standards will not occur during storm runoff. Vegetative filters are systems in which a vegetative area such as pasture, grassed waterways, or even cropland is used for treating feedlot runoff by settling, filtration, dilution, adsorption of pollutants and infiltration.
Generally, vegetative filters have either channelized or overland flow. Channelized-flow systems have various configurations such as a graded terrace channel or grassed waterways, but are simply systems in which flow is concentrated in a relatively narrow channel. In overland flow systems flow occurs as sheet flow less than 30 mm (1.2 in.) deep, with widths ranging from 5 to 6 m (16 or 20 ft) up to possibly 30 m (98 ft).
Much early use of vegetative filter treatment was for the disposal of canning-industry wastes. Mather ( 1969) reported removal of biochemical oxygen demand (BOD) from cannery wastes of 94 to 99 percent during overland flow in a disposal area, although Bendixen et al. (1969) reported only 66 percent BOD removal. Nitrogen removals of 61 to 94 percent and phosphorus removals of 39 to 81 percent were also reported in these two studies.
Sievers et al. (1975) used a grassed waterway filter to treat anaerobic swine lagoon effluent. Willrich and Boda ( 1976) also treated swine lagoon effluent with sloping grass strips. Open feedlot runoff-treatment systems have been reported by Sutton et al. (1976) and Swanson et al. (1975 ). While the degree of treatment varied, these studies indicated that vegetative tilters were effective and potentially acceptable treatment alternatives. No uniform criteria evolved from these studies, however, and variable performance has made environmental authorities hesitate to give blanket approval to this concept. Lybecker (1977) showed that vegetative filters are generally more economical than zero-discharge systems, making them an attractive alternative to small feedlots with minimum capital.