Patent ID: 7156999

Claim:
A method of treating animal manure yielding a final liquid fraction and solid fractions whereby the final liquid fraction has a suspended solids (SS) content of about 3 g/L or lower comprising subjecting at least a part of said manure to a first biological passive flotation step in a flotation unit having a hydraulic residency time (HRT) of about 4 to about 24 hours with a polymer to yield a first flotation solid fraction and a first flotation liquid fraction; a further treatment step selected from the group consisting of subjecting said manure to a coarse solid particles separation step for removing solid particles larger than about 0.05 mm prior to the first floatation to yield a first liquid fraction wherein said first liquid fraction is said part of said manure, and subjecting the first flotation liquid fraction to a further solid-liquid separation step yielding a final liquid fraction.