Biological water treatment process - has biological purificn. step, sedimentation step and controlled sludge recirculation step

摘要

The invention applies to a water treatment with a biological purifin. stage followed by a sedimentation stage, and a controlled recirculation of sludge from the sedimentation stage to the purification stage. The concentration of the recirculated sludge is varied in accordance with the volume of sludge in the purification vessel, or the sludge level in the sedimentation vessel, and for this purpose the sludge is withdrawn from different levels in the sedimentation vessel. A number of similar systems may be operated in series, the sludge from each of the sedimentation stages being recirculated to the first purificn, stage, and sludge being withdrawn from the first sedimentation stage for disposal. USE/ADVANTAGE - This invention is used in the control of biological water treatment processes. The system proposed allows raw water with a continuously varying degree of contamination to be treated )without affecting the quality of the purified water or overloading subsequent purification stages.