Evaluation of Amendment Techniques for Remediating Water Quality of Surface Runoff from Manure-Impacted Soils.

The long term application of animal manures and biosolids to agricultural soils has led to the build up of nutrients in the receiving soils. These excess nutrients, particularly P in surface soils, have the potential to be lost in leaching and runoff, therefore immensely contributing to the impairment of surface water quality. This study evaluated the effectiveness of red mud and brown mud, which are bauxite wastes obtained from the leaching of bauxite to produce alumina, on improving the water quality of surface runoff from manure-impacted soils.  Two red mud samples (ALCOA red mud and ORMET red mud), and a brown mud sample (ALCOA brown mud) were used. The study revealed that the various amendments and application rates evaluated showed the potential of reducing the water extractable (soluble) P, C, Cu and Zn levels of these manure-impacted soils. The efficiencies of these red mud samples were improved by neutralization, however, the 4% application rate of these neutralized red mud samples, and brown mud offered no improvement over the 2% application rate on extractable (soluble) P and C. These amendments showed the potential of increasing the electrical conductivity and sodium adsorption ratio of runoff water from these soils. Five-day biochemical oxygen demand (BOD₅) analysis conducted on the water extract revealed that oxygen demand was significantly reduced due to reduced dissolved carbon resulting from the complexation of organic matter. Most of our findings support those of other researchers and suggest that the 2% application of neutralized red mud to organic manure-impacted soils could reasonably reduce the soluble P, organic C, heavy metals and to a reasonable extent the oxygen demand imposed by runoff water from these soils.