Sewage clarification - in two flock(s) precipitation stages by injecting calcium salt and iron salt in aeration up draught

摘要

A process for the phosphate precipitation and for the final clarification of sewage in basins or ponds includes a biological treatment by aeration, followed by two separate flocculation stages for a sedimentation of the sludge. In each subsequent stage, air or oxygen injection produces a circulatory flow. In the first stage, a calcium salt is added and in the second an iron salt, preferably by a metered admixture to the updraught produced by the aeration. Outside the mixing zone, the mixture passed through an anti-turbulence zone. This creates favourable conditions for the sedimentation and yields an easily processed sewage sludge. The large flocks make the precipitation more efficient.