Activated sludge treatment of waste water - using recirculating tank with aeration point and sensors for max. and min. oxygen levels to regulate degree of aeration

摘要

O2 is introduced into an activated sludge process for treating waste water by using a recirculating aeration tank. The sludge-water mixt. is circulated round at a velocity of 20-30 cm/sec. In one sector of the tank there is an aeration point, where purification due to nitrate formation occurs. The O2 content of the mixt. is monitored straight after the aeration zone by means of a first probe which serves to keep O2 content at that point above a certain min. Second probe is mounted on the opposite side of the tank to the first and serves to limit O2 content to a max. value. Used for long term treatment of waste water. Allows a denitrification plus purificn. process to be carried out by allowing nitrate build up followed by breakdown in the tank. This avoids high nitrate levels passing over to the settling system where they would cause accelerated sludge growth.