Evaluation of Constructed Wetlands for the Waste Management of a Large Scale Swine Production Unit
Abstract
The effectiveness of using constructed wetlands to remove unwanted nutrients, increase dissolved oxygen while at the same time decreasing the biological oxygen demand, and to reduce the levels of the Fecal Coliform Bacteria from a swine operation was evaluated. The indicator of proper waste purification will be the result of testing for the following: ammonia nitrogen, nitrate nitrogen, total phosphorus, total suspended solids, dissolved solids, dissolved oxygen, biological oxygen demand, and Fecal Coliform Bacteria. The wetland was divided into nine connected cells that covered approximately 3.8 hectares. Material was loaded from an anaerobic holding lagoon on four separate occasions during the testing period. As the material passed through the wetland, the vegetation, water column, substrate, and microbial populations functioned as the purification factors in the wetlands. During the sampling period, water was collected from each cell and analyzed for results. The data indicated that the constructed wetlands were effective in the waste management at a large swine production unit. Ammonia nitrogen showed an acceptable decrease, allowing nitrogen to be freed or converted into nitrate nitrogen. Total phosphorus and dissolved solids showed an expected decrease. Total suspended solids showed an overall decrease from the upper cells to the lower cells; however, results fluctuated during the testing period. Dissolved oxygen and biological oxygen demand showed an almost perfect inverse relationship with dissolved oxygen increasing as biological oxygen demand decreased. The removal of Fecal Coliform Bacteria was the most impressive, with the majority of bacteria being removed in the upper cells.