CHEMICAL SEPARATION OF PARTICULATE AND DISSOLVED PHOSPHORUS AND RELEASE FROM DAIRY MANURE

Authors: Dao, Thanh; DANIEL, T. - UNIV ARKANSAS

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2002
Publication Date: 6/18/2002
Citation: DAO, T.H., DANIEL, T.C. CHEMICAL SEPARATION OF PARTICULATE AND DISSOLVED PHOSPHORUS AND RELEASE FROM DAIRY MANURE. JOURNAL OF ENVIRONMENTAL QUALITY. 2002.

Interpretive Summary: Increasing interest exists in manure treatments to chemically bind soluble phosphorus and retain nitrogen in manure before it is applied as many soils in the US contain excessive levels of nutrients due to repeated manure applications. A promising technology is the use of chemical aids in the separation of liquid manure into particulate and liquid fractions to correct the inefficiency of screens and solid separators and the costly loss of waste storage capacity in dairy or swine production. Solids fill retention ponds or lagoons rapidly, requiring frequent maintenance. Chemical coagulants used in the drinking water treatment industry help remove organic and mineral matter and nutrients from the suspension and the disposal of a small volume of solids. Suspension solid content had a clear effect on aggregation and chemical rates. Organic polymers and aluminum and iron salts individually increased the aggregation of particulates in high- solid manure suspensions. A synergistic aggregating action occurred at low concentrations of aluminum and iron chloride with cationic polymers. Co- applications of polymers, fly ash, and Al and Fe salts also reduced excessive amounts of soluble phosphorus in manure-amended soils. Phosphorus reductions were achieved consistently with fly ash and Al and Fe salts in the 10 g/L of slurry in the presence of water treatment polymers. The polymer-amendment treated particulates maintained their stability 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 significantly reduce polymer and metal rates and maximize manure solids and phosphorus removal from typical dairy slurry containing 3 to 10% solids.

Technical Abstract: In confined animal feeding operations, liquid manure systems present special handling and storage challenges because of the large volume of diluted wastes. Wastewater treatment polymers and three mineral P immobilizing chemicals were used to determine dissolved reactive phosphorus reduction mechanisms in high total suspended solid (TSS) dairy manure. Cationic polymers and hydrolyzing Al and Fe salts individually increased particulate aggregation, reducing TSS by 40 and 60% in 30 g L-1 and 100 g L 1 TSS suspensions, respectively. The congealed aggregate entrapped a large amount of wastewater, producing large flocs to potentially facilitate particle filtration in the solid-liquid separation process. At marginally effective polymer rates between 0.01 and 0.25 g L-1, maximal aggregation was attained in combination with 1 and 10 g Al and Fe L-1 in TSS30 and TSS100 suspensions, respectively, exceeding the level of aggregation achieved with individual coagulants. Co-application resulted in reduction of up to 80 and 90% of metal salt and polymer rates, respectively. Solution DRP was reduced consistently when the mixture included fly ash or Al and Fe salts at rates between 1 and 10 g L-1. Higher Al3+ or Fe3+ concentrations re-dispersed particulates and increased solution DRP. Release of environmentally sensitive DRP from soil amended with treated manure was reduced, although the chemical amendments have increased Mehlich-3 extractable P.