Alternative Wastewater Pond Design for Land Applying the Effluent

Before wastewater is recycled on land it must be treated. The extent of treatment prior to land application depends upon the wastewater source, such as low strength (municipal and some industrial) wastewater requiring less treatment than high strength (i.e., livestock and poultry) wastewater. Treatment of wastewater can be as simple as using ponds or more involved by using fully mechanical systems. Recent developments available for designing the Pond-in-Pond (PIP), have made the use of ponds more applicable as a treatment system prior to land application. The objective of the research proposed is to utilize computational fluid dynamics (CFD) to determine and understand the flow mechanics of the PIP. The PIP was sectored into it component parts and evaluated with respect to both fluid flow and particle flow. For comparison purposes, two equally sized ponds are modeled with a design flow of 1 mgd (0.031 m³/s). The velocity profile difference with respect to the pond configuration and the particle settling velocity were used to compare the pond configurations. The solids' retention capacity was significantly higher for the PIP compared to the traditional pond configuration. This was evaluated by examining the mean velocity within the traditional pond and the PIP system had a significantly lower (76%) velocity (p<0.001). Results show how the PIP pond treatment system outperforms a traditional pond system in terms of both consistent effluents and increased organic removal for similar sized units so that it can be sustainably applied to cropland.