Presentation
Manuscript - ASAE Paper #004121 - Adobe Acrobat file (PDF)

An assessment of thirty, single-cell, recycle inactive anaerobic swine lagoons was conducted on 25 farms in Johnson and Greene counties in North Carolina.  Each lagoon was visited one time to determine the lagoon dimensions, depth (supernatant and sludge) and the volume of sludge accumulation.  The nutrient content and land required to apply the contents of 30 inactive lagoons was dominated by the volume lagoon sludge.  These volumes were inadequately described to both the number of years the lagoon was in operation or the number of years after depopulation, even though preliminary results suggested that natural processes may be reducing the sludge over time.  The amount of land required to apply the lagoon contents was found to also be quite variable.  As expected a greater amount of land would be required to apply the contents on the basis of phosphorus rather than an irrigated or incorporated nitrogen application rate.  Lastly, due to variability of observed sludge volume and nutrient mass, engineers or conservationists should not use average values found in this study for making agronomic recommendations.  Rather, sludge and liquid volumes should be measured and matched with corresponding nutrient analyses before closure and land application activities begin to safeguard against the over application of nutrients.
 

Sludge Management and Closure Procedures for Anaerobic Lagoons  - 2000 ASAE Blue Ribbon Award Publication
Ron E. Sheffield, Biological & Agricultural Engineering, NC State University
James C. Barker, Biological & Agricultural Engineering, NC State University
Karl A. Shaffer, Soil Science, NC State University

Sludge is a natural byproduct of anaerobic biological digestion. This dead microbial material, which accumulates over many years in the bottom of anaerobic lagoons is rich in nutrients and organic matter, periodically must be removed from the lagoon. Typically it is land-applied to crops. Improperly managing the sludge volume in a lagoon will result in higher concentrations of nitrogen in lagoon effluent, a faster rate of sludge buildup, and a greater potential for odors the lagoon surface. This document and presentation will discusses several options for removing sludge from anaerobic lagoons. It also outlines the currently approved procedures in North Carolina that should be followed to properly "close" a lagoon or take it out of service.