DESIGN AND OPERATIONAL CONSIDERATIONS FOR THE LARGEST SBR PLANT

The paper describes design and operational considerations for the largest SBR plant in the world presently being constructed in Dublin, Eire for a population equivalent of 1.8 million. Site constraints, keeping the existing primary treatment going and life cycle costs dictated the design in an open competition. Stacked SBR's could fit on the site and allowed construction while keeping the present plant operational. Life cycle costs over 20 years demanded that the overall energy balance be taken into account as well as the quantity of sludge produced. The combined sewers with flat grades required high rate primary treatment. Partial nitrification was required. denitrification was dictated by the low alkalinity. Only about 50% of the wastewater will be nitrified while the remainder will get only high rate treatment. The primary and secondary sludge will be passed through a heat hydrolysis process to increase gas production and improve dewaterability thus reducing the sludge mass produced as well as the water associated with the sludge since this must be evaporated. The higher sludge breakdown with heat hydrolysis will make the plant independent of outside energy for sludge digestion and drying. The operation of the plant during storm flows and with one unit out will be described.