Date of Award
Master of Science
Environmental and Soil Sciences
John R. Buchanan, Forbes R. Walker, Daniel C. Yoder
Municipal sewage disposal and soil erosion control from highly disturbed sites are both large scale issues of environmental concern. Composted biosolids (CBS) and shredded wood have the potential to be applied as soil cover to address both disposal and erosion issues. There is a lack of information on the use of these products on steep slopes, typical of construction sites. The objective of this study was to evaluate the use of CBS for reducing erosion and establishing vegetation on a cherty, slightly compacted, Fullerton Series sub-soil embankment, with an average slope of 46.5 percent. The study was conducted at the Knox County Green Waste Recycling facility in Solway, TN on a spoil pile created during construction of the facility. Twelve plots, each measuring 6.5 meters long by 2.5 meters wide, were used with three replications each of four treatments: bare (uncovered, unseeded), straw mulch, CBS, and a 50/50 mixture of CBS and shredded wood produced on site. Prior to the application of treatments, covered plots were seeded with a standard mixture of seed for erosion control used by the Tennessee Department of Transportation. Total runoff volume and sediment were measured following each rain event, and digital photographs were taken weekly to record vegetation growth from June 24 to October 31. Composted biosolids was as effective as straw at reducing total sediment (95.7 percent and 96.0 percent reductions respectively). The 50/50 mixture achieved the greatest sediment reduction of 96.4 percent. The application of CBS appeared to have the greatest positive impact on establishing vegetation. Vegetation on the straw mulch plots was concentrated on the lower portions likely due to the seed washing down slope following early rain events. The 50/50 treatment reduced total runoff by 69.6 percent, and the CBS treatment by 58.5 percent compared to plots left bare. Total runoff on straw plots was reduced by 47.0 percent compared to plots left bare. The results demonstrate that CBS can be used effectively to reduce soil erosion and establish a vegetative cover on steep slopes of highly disturbed sites, while serving simultaneously as an alternative means of sewage sludge disposal.
Fisher, Justin Lee, "Composted Biosolids as a Soil Cover on Steep Slopes. " Master's Thesis, University of Tennessee, 2012.