Effects of solid levels and chemical additives on removal of solids and phosphorus in swine manure

Experiments were conducted to determine the effect of solid levels on natural sedimentation of swine manure. Total solids (TS) levels of 0.5, 1.0, 2.0, 4.0, and 6.0% were evaluated. Natural sedimentation was impeded at higher than 2.0% and also at lower than 1.0% TS concentrations. Two flocculants (ferric chloride and aluminum sulfate) commonly used in the municipal wastewater treatment industry were then evaluated for their enhancement of natural sedimentation and concomitant removal of phosphorus from swine manure. Each flocculant was evaluated at five levels-0 (control), 500, 1,000, 1,500, and 2,000 mg/L-on swine manure with an adjusted TS level of 1.0%. At dosage levels of 1,500 mg/L (5.4 mM Fe+3), ferric chloride removed 76% suspended solids (SS) and 86% phosphorus, while aluminum sulfate at the same dosage level removed 96% SS and 78% phosphorus. Unaided natural sedimentation at this TS concentration removed 66% and 42% of the SS and phosphorus, respectively. Chemical flocculation can, therefore, be an effective method of removing solids and phosphorus in swine manure.