Methods and apparatus for treating animal manure

Abstract

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 3g/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, said method comprising a further treatment. An apparatus for treating animal manure comprising a main flotation unit having a HRT of about 4 to about 24 hours, said main flotation units including skimming means for removing floating solids from at least a portion of the surface of the manure and dredging means for removing settled contaminants from at least a portion of the bottom of the tank, whereby at least a part of said manure is directed to the main flotation unit wherein it is separated in a first floating solids fraction, a second liquid fraction and a first settled solids fraction and wherein the second liquid fraction has a SS content of about 3g/L or lower.

1 . An apparatus for treating animal manure by biological passive flotation comprising a main flotation unit having hydraulic residency time (HRT) of about 4 to about 24 hours, said main flotation unit[s] including skimming means for removing floating solids from at least a portion of the surface of the manure and dredging means for removing settled contaminants from at least a portion of the bottom of the unit, whereby at least a part of said manure is directed to the main flotation unit wherein it is separated in a first floating solids fraction, a second liquid fraction and a first settled solids fraction and wherein the second liquid fraction has a SS content of about 3 g/L or lower.  
     
     
         2 . An apparatus as recited in  claim 1 , further comprising a coarse solid particles separation means, and a secondary flotation unit having a HRT of about 0.5 to about 4 hours, said secondary flotation unit including skimming means for removing floating solids from at least a portion of the surface of the manure, dredging means for removing settled contaminants from at least a portion of the bottom of the secondary flotation unit, whereby the manure is directed to coarse solid particles separation means wherein it is separated in a first liquid fraction and a first coarse solids particles fraction, the first liquid fraction is then directed to the main flotation unit wherein it is separated in a first floating solids fraction, a second liquid fraction and a first settled solids fraction, the second liquid fraction is then directed to the secondary flotation unit wherein it is separated in a second floating solids fraction, a third liquid fraction and second settled solids fraction, whereby settled solids fractions and floating solids fractions are skimmed and dredged away, respectively, from the liquid fractions and wherein the third liquid fraction has a suspended solid content of about 3 g/L or lower.  
     
     
         3 . An apparatus as recited in  claim 1 , wherein said coarse solid particles separation means is a decantation tank.  
     
     
         4 . An apparatus as recited in  claim 1 , wherein said main flotation unit has a HRT of at least about 5.5 hours.  
     
     
         5 . An apparatus as recited in  claim 1 , wherein said animal manure is pig manure.