State of the art for animal wastewater treatment in constructed wetlands

Abstract

Although confined animal production generates enormous per-unit-area quantities of waste, wastewater from dairy and swine operations has been successfully treated in constructed wetlands. However, solids removal prior to wetland treatment is essential for long-term functionality. Plants are an integral part of wetlands; cattails and bulrushes are commonly used in constructed wetlands for nutrient uptake, surface area, and oxygen transport to sediment. Improved oxidation and nitrification may also be obtained by the use of the open water of marsh-pond-marsh designed wetlands. Wetlands normally have sufficient denitrifying population to produce enzymes, carbon 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. Wetlands are also helpful in reducing pathogen microorganisms. On the other hand, phosphorus removal is somewhat limited by the anaerobic conditions of wetlands. Therefore, when very high mass removals of nitrogen and phosphorus are required, pre- or in-wetland procedures that promote oxidation are needed to increase treatment efficiency. Such procedures offer potential for enhanced constructed wetland treatment of animal wastewater.

Nutrient removal by floating aquatic macrophytes cultured in anaerobically digested flushed dairy manure wastewater

“…The application of aquatic plants for treatment of animal wastes has mainly involved constructed wetlands. Currently, livestock producers in at least 26 states across the USA use constructed wetlands to treat animal production wastewater (Hunt and Poach, 2001). Constructed wetlands have an appeal as a farm waste management practice because they are a low cost, simple technology, and ideally require little maintenance or management after construction (Hammer, 1992).…”

Constructed wetlands for environmental pollution control: A review of developments, research and practice in Ireland

“…For instance, Zhao et al, (2004a) reported on the use of a novel laboratory-scale reed bed system for the treatment of an animal farm wastewater with a BOD 5 value of 441-3150mg/l while Hunt et al, (2001) detailed the successful application of CWs to the treatment of wastewater from dairy and swine operations.…”

Two strategies for improving animal farm wastewater treatment in reed beds

“…These include nuisance odours, pathogens, concentrated wastewater, inadequate land treatment sites, residential encroachment and new regulations (Hunt and Poach, 2001). In particular, the steady intensification of such farming practices have led to increasing levels of environmental pollution, including degradation of the water quality of downstream ecosystems.…”

“…Hunt and Poach (2001) reported that the common practice on most animal farms is to apply both solid and liquid waste to land for terminal treatment. In Ireland, it is reported that dairy parlour washings are treated mainly by land spreading with low irrigation systems (Healy et al, 2007).…”

“…In particular, reed bed treatment systems (RBTSs) (a form of CWs planted with reeds) offer a cost-effective treatment option for such wastewaters and their use for the treatment of animal farm wastewaters have emerged strongly in the last decade. Hunt and Poach (2001) reported that there are at least 26 states in the US where livestock producers are using CWs to treat animal wastewaters. Several authors have also reported on the use of CWs/RBTSs for the treatment of animal farm wastewater (Copper and Testa, 1997;Reddy et al, 2000, Hunt andPoach, 2001;Zhao et al, 2004).…”