Drainage Systems for Land Treatment of Wastewater

Simulation methods for design and evaluation of drainage systems for wastewater land treatment sites are presented. The methods are based on the water management model, DRAINMOD, for describing the performance of an artificially drained land treatment system over a long period of climatological record. The methods are demonstrated by considering an example of wastewater application on a poorly drained soil area near Wilmington, N.C. Several drainage designs and application strategies are evaluated to determine their effects on the amount of wastewater that could be treated and how that amount changes from year to year with weather conditions. Effects on water table depth outflow volumes and required wastewater storage are also analyzed. When wastewater application is limited by drainage conditions of the site, more water can be treated by applying small amounts frequently than with larger amounts on a less frequent basis. Results showed that DRAINMOD can be used to optimize the drainage system design for a given land application site.