Methodology for the sizing of storage requirements of slow rate land treatment systems using various management options

Abstract

Slow-rate land application is a means of treating and making beneficial use of wastewater. The cost of treatment of wastewater with the slow-rate system is dependent on the sizing of the storage requirements and the management of the system. Management decisions such as crop selection, choice of cultural practices, leaching scheduling, and water-nutrient application have a direct bearing on sizing of the effluent storage pond.

In this study a numerical simulation method is used to develop a logical storage sizing methodology. A statistical method is presented to attach risk of failure and uncertainty involved in the decision making with the sizing of the storage. Stochastic mass balance models are developed to keep track of flow of water, nutrients, and dissolved solids in the sub-systems of the slow-rate system. A stochastic optimization model for maximizing application rate of water and nutrients at all times is formulated and this in return minimizes the need for storage.

The role of management decisions on the size of the system and treatment efficiency is evaluated. Nutrient level regulation through aging of wastewater is presented as a means of minimizing pollution.