World’s Largest Retrievable Fine Bubble Aeration System for an Activated Sludge Plant Installed at a P & P Mill Without Production Lost. Part II, 2002 Environmental Conference Proceedings

J. C. Paradis, A. Durocher and H. C. Lavallée

The diffused aeration system proposed by Sanitaire Inc. includes 22 retrievable grids fed from two independant lines, one for the selector and the other for the first of the two bioreactors (basin #1). Two grids are for the selectors (1320 diffusers) and the 20 others are for the first basin (8060 diffusers). The air is supplied by three centrifugal blowers having a total capacity of 24000 SCFM.

The DO was automatically controlled in each basin with a DO probe, a control valve, and a flowmeter. The air distribution between lines was made through another loop based on the pressure. A detailed procedure was established in order to minimize the impact on the WWTP and on the mill operation and production. All the blowers and piping were installed and completed prior to proceeding with the diffusers. A laser was used to guide and assist in the accuracy of the installation.

Since the startup of the new aeration unit in September 2000, the WWTO was able to adequately treat 12-15 t/d of BOD without any breakdown or maintenance. The automatic control loops have maintained an uniform oxygen residual of 2 ppm in the basins. Results obtained from the pilot, respirometry, and biosorption were all confirmed and the mill is respecting all standards. Biosorption observed in the selector is efficient and greatly contributed to reduce filamentous bulking.