Land Application of Untreated Industrial Waste Water

Abstract

AbstractExcessive pretreatment of waste water prior to land application unduly increases the cost and energy requirement of land treatment systems. This study was conducted to determine if untreated industrial waste water can be applied to soil without adversely affecting crop growth and soil properties or posing a ground‐water pollution hazard.Untreated (UW) and treated (TW) waste water were diverted from the treatment plant at a fiberboard mill and spray‐irrigated on fescue‐grass (Festuca arundinacea Schreb) on Cecil soil (clayey kaolinitic, thermic Typic Hapludult) at 1.4 cm/week. After 2 years the treatments were changed to 1.5, 2.0, and 3.0 cm UW/week and continued for 2 more years.Grass yields with UW and TW were equal to or greater than yields with inorganic fertilizer and no irrigation (control treatment). Recovery of waste‐water‐applied N via crop harvest ranged from 20 to 30%. Analysis of washed and unwashed grass samples showed that increased Mn concentrations were due to waste‐water solids adhering to the sample, rather than to increased Mn uptake. Concentrations of Ni, Pb, and Cr of unwashed samples were increased slightly but were far below concentrations toxic to livestock.Soil nitrate concentrations resulting from UW applications were generally not significantly different from concentration in the control treatment except when UW contained appreciable quantities of inorganic N. There was evidence that denitrification was a significant N sink.Waste‐water irrigation increased concentrations of soil P, K, and Ca and increased soil pH to 7.4–7.8. Sodium accumulated in the subsoil to an exchangeable‐Na percentage of 10.Results of the study showed that extensive pretreatment was not necessary prior to irrigation with the waste water.