Submitted to: Water Environment Federation
Publication Type: Proceedings
Publication Acceptance Date: April 10, 2003
Publication Date: April 25, 2003
Citation: DAO, T.H. 2003. PARTICLE DESTABILIZATION AND REMOVAL FROM CONCENTRATED DAIRY MANURE SUSPENSIONS. CHAPTER 17-4. PROCEEDINGS OF JOINT RESIDUALS AND BIOSOLIDS MANAGEMENT. SPECIALTY CONFERENCE: PARTNERING FOR A SAFE SUSTAINABLE ENVIRONMENT, FEB. 19-21, 2003. BALTIMORE, MD. CD-ROM No. 0330. WATER ENVIRONMENT FEDERATION, ARLINGTON, VA.
Interpretive Summary: Phosphorus is most often the element limiting eutrophication or algal blooms in surface water bodies and estuaries. 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 as many soils in the United States contain excessive levels of nutrients due to repeated heavy applications of animal manure. 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 or swine production. The low separation efficiency has led to the costly loss of capacity in waste storage facilities. Particulates fill up retention ponds or lagoons rapidly, requiring frequent maintenance and cleaning. Suspension Total suspended 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. Therefore, the synergism that exists between coagulant types can be optimized to reduce chemical use and maximize manure solids and phosphorus removal from liquid manure suspensions containing high total solids.
Post-excretion treatments of animal manure to remove suspended solids and chemically remove dissolved-reactive phosphorus (DRP) before manure is applied to fields has become a focus issue in national strategies for managing animal residuals. A promising management and processing technology to sequester manure P and other organic nutrients is the separation of concentrated liquid manure into particulate and liquid fractions. However, the inefficiency of mechanical separators or screening has led to the rapid loss of capacity in storage ponds or lagoons that require frequent cleaning. Mechanisms of particle destabilization in wastewater suspensions include surface charge neutralization, interparticle bridging, and particle diffuse-layer compression. Combinations of these mechanisms were operational in our optimization approach to enhancing solid-liquid separation in concentrated dairy manure suspensions. Water treatment polymers and mineral P-immobilizing chemicals [aluminum sulfate, iron chloride, and coal-combustion ash] were co-applied to determine particle destabilization efficiency and DRP reduction mechanisms in high total suspended solid (TSS) dairy manure. In the TSS range between 30 and 100 g L-1, co-application exceeded the level of aggregation achieved with individual manure additives. Solution chemistry was the overriding considerations in enhancing particle destabilization with organic polymers-hydrolyzing metal salt combinations. Surface reactivity of the coal-combustion ash played more of a key role in the particle destabilization and P recovery processes. The experimental results suggest that the synergistic effect that exists between chemical aggregation aid chemicals can be optimized to achieve reduction in coagulant inputs, while the knowledge of key manure slurry characteristics and controlling mechanisms for particle destabilization and P recovery improve manure treatment efficacy.