Submitted to: International Symposium on Agricultural & Food Processing Wastes Proceeding
Publication Type: Proceedings
Publication Acceptance Date: 5/10/1995
Publication Date: N/A
Interpretive Summary: Over one-sixth of the $175 billion agricultural economy consists of animal production. Increasingly, large-scale production occurs in confinement where enormous per-unit-area quantities of waste are generated. Therefore, to remain viable, animal production enterprises must have functional and sustainable waste management systems. These systems must process both liquid and solid wastes for dairy and swine enterprises. Constructed wetlands have received attention in recent years as a method of animal wastewater treatment. Wetlands have been used successfully for advanced treatment of municipal and residential wastewaters in the United States and around the world for over three decades. Compared to conventional systems, they have less construction, operation, and energy costs but more flexibility in pollutant loading. However, there are limited data for the treatment of animal wastewater in constructed wetlands. When wetlands were ecombined with grass filter strips, wastewater was treated at much higher rates than possible with standard application to cropland. However, solids removal prior to wetlands treatment is essential for their long-term functionality. Cattails and bulrushes are commonly used in constructed wetlands. When very high mass removal of N and P is required, pre- or in- wetland procedures that promote oxidation are needed to increase treatment efficiency.
Technical Abstract: Confined animal production generates enormous per-unit-area quantities of waste, and wastewater from dairy and swine operations has been successfully treated in constructed wetlands. However, solids removal prior to wetlands treatment is essential for long-term functionality. When wetlands were combined with grass filter strips, an application of swine wastewater containing 14 kg ha-1 day-1 of N was treated to over 95% N removal. Plant are an integral part of wetlands, and cattails and bulrushes are commonly used in constructed wetlands. However, bulrushes transport more O2 to sediment. Improved oxidation and nitrification may also be obtained by the use of the open water strips of marsh/pond/marsh designed wetlands. Wetlands normally have sufficient denitrifying population to produce enzymes, C to provide microbial energy, and anaerobic conditions to promote denitrification. However, the anaerobic conditions of wetland sediments limit the rate of nitrification. Thus, denitrification of animal wastewaters in wetlands is generally nitrate-limited. Phosphorus removal is also somewhat limited by the anaerobic conditions of wetlands. Therefore, when very high mass removal of N and P is required, pre- or in- wetland procedures that promote oxidation are needed to increase treatment efficiency. Such procedures offer the greatest potential for improved treatment capacity for constructed wetland treatment of animal wastewater.