Ozone Addition to Prevent Solid-Liquid Separation Troubles in Wastewater Treatment (Gordona Scum Suppression by Adding Ozone in the Return Sludge Line)

摘要

At the Todoroki Wastewater Treatment Plant of Kawasaki City, solid-liquid separation troubles due to the growth of Gordona amarae and scum formation occurred in the oxygen activated sludge process, and measures to prevent these troubles have been taken. Since 1994, pilot plant experiments for adding ozone to the return sludge have been made. To add ozone to the return sludge, an ozone contact tank is provided in the return sludge line and the sludge is brought into contact with ozone in this tank before it is allowed to flow into the aeration tank. The ozone addition rate is 1.5-3 mg/l return sludge on a continuous basis and the ozone contact time is 1.5-2 minutes. After 1 or 2 weeks, scum suppression occurs. It is to be mentioned that this system is applicable even to the wastewater treatment plants having the aeration tank not covered, and as compared with the system to add ozone in the aeration tank, it requires small installation space and ozone gas exhaust measures can be taken easily.