| 摘要 |
Activated or humus sludge which has been thickened (for example, by air flotation) to a solids content of at least 2% is caused to spontaneously flocculate by treatment with a base to raise the pH of the thickened sludge to more than 8 and then acidified, preferably to a pH of 1 to 4. The sludge is generally allowed to gel by standing for one to five hours after base treatment and before acidification; heat treatment is unnecessary and the sludge can be at ambient temperature throughout, The flocculated sludge can be readily dewatered and further processed to produce a sterile high protein dried product of low heavy metal content, for use as a fish or animal feed or organic fertilizer. |
