Impact of anaerobic lagoon management on sludge accumulation and nutrient content for dairies
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abstract
The contents of twelve primary dairy lagoon cells under different management practices in three central Texas counties were evaluated for sludge accumulation and physicochemical characteristics. Composite samples were comprised of the wastewater column from the top of the lagoon to the top of the dense sludge layer. The composite samples were thought to represent a slurry mix typical of agitated lagoon material intended for land disposal. Analyses included pH, total solids (TS), volatile solids (VS), total Kjeldahl nitrogen (TKN), total ammonium-nitrogen (NH4-N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), zinc (Zn), copper (Cu), manganese (Mn), and electrical conductivity (EC). Statistically, lagoon management practices and treatment effectiveness in terms of reduced sludge accumulation and nutrient content were not strongly linked. However, some practices appear to influence the physicochemical properties of the slurry mix, including use of fresh flush water, increasing the number of treatment cells, and separation of dry lot runoff. Total Kjeldahl nitrogen, P, and K were linearly correlated to TS, indicating higher nutrient concentrations in the anaerobic lagoon sludge. The resultant elevated nutrient levels in the slurry mix, compared to supernatant values, will require greater land areas to meet P-based regulations. Land applying a lagoon slurry mix will require approximately two and a half times as much land area compared to N-based application rates. Consideration of best management practices (BMPs) may be advised to alleviate lagoon clean-out and sludge disposal challenges.
