OPTIMUM COAGULANT AND FLOCCULANT CONCENTRATIONS FOR SOLIDS AND PHOSPHORUS REMOVAL FROM PRE-SCREENED FLUSHED DAIRY MANURE

Concentrated animal feeding operations (CAFO) using water-flush systems creates excessive manure slurries containing high solids and phosphorus (P). Using pre-screened slurry (1.0 mm) in Part I, optimum combination concentrations for dewatering for two coagulants (AlCl3 and FeCl3) and one flocculant (255G-PAM) were identified. In a follow-up separate experiment in Part II, the identified optimum concentrations were evaluated for their total solids (TS) and total P (TP) removal capability using the same type of pre-screened slurry (1.0 mm) in combination with a 0.5-mm static screen. In Part I, aluminum (Al) and iron (Fe) alone increased dewatering 70 to 80 times compared to the control, decreased filtrate pH as their respective concentrations increased, and decreased filtrate total dissolved P (TDP). Coagulants combined with 255G-PAM enhanced the dewatering capabilities 1.5 to 1.7 times at lower coagulant concentrations. Interaction between the coagulants and 255G-PAM dewatered the slurry and removed P more efficiently than the control or coagulants alone. In Part II, the TP removed was directly correlated to the quantity of screened solids removed (R2 = 0.92). Treatments (on screen) removed 3 to 8 times more TS and 6 to 25 times more TP than the control, with mean recoveries of 100% and 76% for TS and TP, respectively. Interaction between the coagulants and 255G-PAM removed TS and TP more efficiently compared to the control and coagulants alone. Treatments reduced the amount of TDP in the filtrate 87 to 182 times, demonstrating this technology has potential for improving manure management provided chemical treatment can be combined with solid separation on a practical and commercial scale.