Characterization of pig slurry with reference to flocculation and separation.

Pig production is concentrated in large farms, increasing the need to export excess nutrients, so manure separation would be useful to concentrate the nutrients. We examined the physicochemical properties of pig manure pertinent to flocculation and separation. Manures from three farms were stored for 3 months at 13 degrees C. The organic pools in the manure did not vary significantly during storage, so microbial metabolism was low and storage was of minor importance to separation. The manure contained highly charged particles and surface charges did not vary between the manures. This implies that the polymer doses required for flocculation can be determined directly from the manure dry matter content and that highly charged, high-molecular-weight cationic polymers can be used. Phosphorus was mainly found in the particulate fraction as struvite and was retained in the solids fraction at high pH. Thus, pH adjustment can control the amount of dissolved phosphorus in manure.