Technical Bulletin No. 0150: Recent Studies of Irrigation Disposal of Pulp Mill Effluents

The attached National Council technical bulletin was first issued in 1961. It reported on a then active investigation of land disposal of spent process waters from pulp mills. This method of disposal was then the subject of active interest in the industry. Irrigation disposal is both a physical and biological process, the percolation of the liquid through the soil being physical and the assimilation of the organic matter content of the waste being biological. Soil characteristics determine the percolation rate while the microbially active surface layer of the soil is responsible for oxidation of the organics. These two factors can be both used and abused; hence both volume and organic strength of the waste applied per acre of soil of known characteristics must be controlled, for its capacity is indeed limited. Since little basic information on this subject was then available, the National Council's West Coast Regional Center project undertook to establish basic parameters for typical soils, both with and without cover crops. Also, the mechanism and degree of purification obtained on percolation through the soil was investigated. In addition to these studies, field experiments carried on by individual mills were followed closely.