by: Charles L. Wax, Jonathan W. Pote, Michael E. Brown
Volume 2009, No. 3, 1 Jun 2009
Disposal of wastewater from large-scale swine production facilities in the southern region of the U.S. is increasingly problematic as production facilities increase and regulations governing disposal become more restrictive. No-discharge systems are attractive or even mandatory for many producers. In such systems, wastewater is pumped from a storage lagoon when a certain level of storage is reached, and proper disposal depends on evaporation, infiltration into the soil, and on a crop's ability to utilize some nutrient such as nitrogen or phosphorus at that time. Under the control of climate in the region, lagoon levels rise during periods of precipitation while the soil becomes wet and the net water requirement of plants decreases, precluding irrigation. Wastewater volume is therefore typically high du ring winter and spring when pumping would be ecologically damaging, and low during summer and fall when conditions are more often suitable for successful land application. Consequently, at the moment of greatest need this type of disposal system is not operational, and spills or illegal discharges may occur. This study uses daily computer simulation over a 45-year period to test how well five management strategies could remedy this offset distribution of wastewater supply and demand. Pumping once each year on planned dates of the 15th of June, July, August, and September do successfully shift the time of necessary pumping out of the winter and spring and into the growing season. An annual September 15 th pumping of lagoons is recommended as the most efficient management plan for avoiding illegal overflows and emergency pumping at times when land application will not be successful.