Former and present landfill techniques at the Filbornaplant in Helsingborg, South Sweden are compared withrespect to impacts on the environment. This includes thepotential for nutrient recovery and heavy metalimmobilisation in the waste residue. The results showthat optimised landfill bioreactor-cells have a higherturn-over rate for organic matter compared to the formerlandfills, whereas the retention capacity for heavymetals in both systems was surprisingly high. Full scaleleachate data, as well as a laboratory leachingexperiments confirmed the role of bioreactor cells asanaerobic filters enabling a separation of nutrients froma mixed waste, while the toxic metals are retained. Theconclusion of this article is that by simple measures, thebiological processes can be optimised, resulting inhigher turn-over rates for organic matter and thusaccelerated waste stabilisation.

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.