Eugene/Springfield Water Pollution Control Facility 1984-1991

New Search

i SCCt10II D: PLANT OPBRATIONS Rather than using drinking water, W2 water (wa- ter left from the treatment process) is used for a variety of purposes at the plant and provides a considerable savings. The W2 water is used as seal water for many pumps; as cooling water for equip- ment,such asengine generators; and as wash water for cleaning basins, clarifiers, and equipment. The W2 water also is used to irrigate lawns and flower beds, to dilute and mix chemicals, and to clean out channels and clarifiers. kit is available for emergency repairs. SLUDGE THICKENING • Emergency Scrubber System The emergency scrubber system, which in the event of a major spill can neutralize up to two tons of chlorine or sulfur dioxide, ensures the safety of plant employees and the public. Scrubber opera- tioncan beactivated manually from five locations at final treatment, any DCS station, or can be started automatically if a leak is detected in the handling or evaporator room by the chlorine and sulfur dioxide leak detectors. Main components of the scrubber system are leak detectors, a duct system connecting to handling areas, an exhaust fan, a caustic supply system, and a plastic, media-filled scrubber tower. The exhaust fan draws contaminated air from the handling rooms and blows it through the bottom of the scrubber. The caustic pump supplies a 10 percent solution of caustic to the upper portion of the stack. Theplastic-type media in the scrubbercauses the caustic solution to "rain down" through the counterflow of contaminated air rising up the scrubber tower. The chemical reaction that occurs between the caustic and chlorine or sulfur dioxide vapors neutralizes the harmful effects of the gases, which are then discharged from the 20-foot stack Page 25 above the roof of the Final Treatment Complex.. Spent caustic is recycled back to the main caustic storage tank. Although no major leaks have occurred, the sensi- tivemonitoring equipmenthasactivatedthe scrub- bersystem when minor leaks were detected during routine tank changes. The system is manually tested each week. Aone-ton chlorine tank repair Waste activated sludge is thickenedbefore the digestion process using two methods. From May to October, sludge is thickened by dissolved air flotation. From November through April, when odors are more easily controlled, waste activated sludge is co-thick- ened with raw sludge in the primary clarifiers. The capac- ity of existing thickening equipment is limited, and operators are investigat- ing additional equipment needs. • Flotation Thickener The flotation thickener was one of the few unit processes incorporated into the new facility from the old Eugene trickling filter plant. Based on the manufacturer's loading rates, design engineers pre- dicted that the flotation thickener and the old gravity thickener could handle plant waste sludge production through design year 2000. PERFORMANCE: The flotation thick- ener has not been able to effectively thicken waste sludge flows consistently. The thickener has been pushed to and beyond capacity many times in the last two years. Sludge conditioning with poly- mer has improved thickening but not enough to handle all waste sludge flows. Sludge that cannot be entirely processed through the flotation thickener must be co-thickened with raw sludge. The flota- tion thickener also has had many me- chanical failures and high maintenance costs. Plant effluent diffuser tubes are irupected prior to their irutallation in the bed of the Willamette River.