Submitted to: Certified Crop Advisors Advantage
Publication Type: Trade Journal
Publication Acceptance Date: November 14, 2003
Publication Date: July 28, 2004
Citation: Dao, T.H., Daniel, T.C. 2003. Particulate and dissolved phosphorus chemical separation and phosphorus release from treated dairy manure: Continuing Education Self-Study Course. Certified Crop Advisor AgProfessional 12/2003:37-41. http://www.agprofessional.com.
Interpretive Summary: Monthly feature articles on a major production agriculture-environment issue are featured in the AgProfessional magazine of The Certified Crop Advisor Program of the American Society of Agronomy as continuing education self-study courses and qualifying exams. The issue of animal waste management and an alternative solution to the problem of managing liquid manure volume and manure phosphorus are discussed in this article. There is increasing interest on post-excretion treatments to chemically bind or remove soluble phosphorus and retain nitrogen in manure before it is applied to fields. Many soils receiving repeated applications of animal manure in the United States contain excessive levels of nutrients, phosphorus in particular. A promising technology to sequester manure phosphorus and other organic nutrients is the separation of liquid manure into particulate and liquid fractions to correct the inefficiency of mechanical liquid-solid separators used in dairy cattle production. The low separation efficiency has led to the costly loss of capacity in waste storage facilities. Manure solids fill up retention ponds or lagoons rapidly, requiring frequent maintenance and cleaning. Improving the solid-liquid phase separation process by chemical coagulants used in the drinking water treatment industry helps remove organic and mineral matter and nutrients from the suspension and the disposal of a relatively small volume of solids. As chemical amendments and methods of applications largely depend upon manure characteristics such as particle size, total suspended solid content, or pH, concentrations of polymers or mineral amendments must be optimized to benefit from synergistic action that exist in their individual modes of action. Suspension total solids had a clear effect on aggregation and rates of polymer and amendment. Organic polymers and aluminum and iron metal salts individually increased the aggregation of particulates in high-solid dairy manure suspensions. A synergistic aggregating reaction occurred at low concentrations of aluminum sulfate and iron chloride with cationic polyacrylamide and polyamine polymers. Co-applications of polymers and mineral amendments also reduced excessive amounts of soluble phosphorus in manure-amended soils to reduce offsite transport risks. Reductions in soluble phosphorus were achieved consistently with fly ash and Al and Fe salts in the 10 g L-1 of suspension in the presence of organic water treatment polymers. The polymer-amendment treated solids remained stable in soil. Release of soluble phosphorus from soil amended with treated manure was reduced. Therefore, the synergism that exists between coagulant types can be optimized to reduce chemical use and maximize manure solids and phosphorus removal from concentrated liquid manure suspensions containing high total solids.
In confined animal feeding operations, liquid manure presents special challenges in handling, storage, and manure nutrient beneficial reuse because of the large volume of diluted wastes. Organic polymers and mineral P immobilizing chemicals increased manure particulate aggregation to concentrate the solid fraction. As chemical amendments and methods of applications largely depended upon manure characteristics (particle size, total solid content, pH), concentrations of polymers or mineral amendments must be optimized to benefit from any interaction or synergism that exist in their separate mechanisms of action. Suspension total solids had a clear effect on aggregation and rates of polymer and amendment. A synergistic aggregating reaction occurred at low concentrations of aluminum sulfate and iron chloride with cationic polyacrylamide and polyamine polymers. Co-application of polymers and mineral amendments also reduced excessive amounts of DRP in manure-amended soils to reduce offsite transport risks. Reductions in DRP were achieved consistently at all rates of fly ash and hydrolyzing metal salts at rates less than 10 g L-1 in the presence of organic water treatment polymers. The polymer amendment treated particulates remained stable in soil. Release of DRP from the soil amended with treated manure was reduced. Therefore, the synergistic effect that exists between chemical aggregation aids should be optimized to achieve chemical input reduction and maximize manure particulates and phosphorus removal from liquid manure suspensions containing high total solids.