The Effect of Waste Water Reuse in Cold Regions on Land Treatment Systems

Abstract

AbstractThe effect on ground water quality and soils and vegetation of treatment and disposal of municipal/industrial waste water on land in cold regions was investigated using six outdoor test cells. Winter application of waste water was feasible even at very cold air temperatures (<0.0°C) at the New Hampshire test site. High NO3‐N concentrations were observed in all treatments (5–15 cm/week) in both soils in early summer. This was explained as leaching of NH4‐N stored over the winter months after its oxidation to NO3 in early spring. Over the 12‐mo period of study, removal of organic C, BOD, suspended solids, fecal coliform bacteria, and phosphorus by the two soil types used (a Windsor sandy loam and a Charlton silt loam) was essentially complete. These had very little or no effect on ground water quality. The principal mechanism for nitrogen removal was found to be plant uptake, which was seasonally dependent. Application of 15− cm of secondary effluent per week to a sandy loam soil was not feasible because of the presence of > 10 mg/liter NO3‐N in the leachate for > 9 mo/year. Application of salts for road deicing during winter resulted in relatively higher concentrations of salts and Cl in the ground for a short period of time. No efforts were made to apply waste water according to plant need. Preapplication treatment is not necessary for the renovation of waste water by the soil‐plant systems. Movement of applied heavy metals to a depth of 15–30 cm in the high treatment soil was thought to be a result of a drop in soil pH resulting from this treatment. In all other treatments, heavy metals were confined to the top 15 cm of the soil.