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' Simifar Project Experience 6-5 of a high-rate Superpulsator clarifier that took up less room and exhibited lower costs than the flocculators and tube settler clarifiers previously piloted by the water company. The piloting program also included granular activated carbon filters, which had been recommended but not yet piloted. The treatment plant design includes preoxidation, high-rate clarification using Superpulsators, and granular activated cazbon filtration for removing color, TOC, iron, manganese, and THM precursors from the combined raw water sources. Disinfection is achieved through sodium hypochlorite, and sodium carbonate and zinc orthophosphate are used for conosion control. Feed systems provide liquid fluoride, alum, and sodium aluminate. The facility also includes a sludge dewatering system that uses high-solids centrifuges and dry-lime conditioning. The existence of high concentrations of manganese and very high color and organics in one of the source wells complicates treatment since the system blends its sources before reaching the treatment plant. A major design issue involved the processing and disposal of the alum sludge generated in the treatment process. Typical low-cost solutions for sludge disposal, such as on-site lagoons, drying beds, or direct discharges to a sanitary sewer, were either not allowed by the local regulatory agencies or not economically feasible. Pilot testing had determined that plate-and- frame presses were not effective in dewatering the alum sludge, and additional testing indicated that centrifuges would provide the necessary sludge dryness. Designed to process sludge from the spent washwater and clarifiers, the system uses a sludge holding tank prior to centrifuge dewatering, resulting in a minimum of 20 percent solids content, thereby permitting disposal in an off-site landfill. Design work was completed on time and within budget. At the client's request, M&E accelerated completion of the work while maintaining high quality standards. Metcalf & Eddy continues a close advisory relationship with the client for ongoing work. Massachusetts Water Resources Authority, Boston Metcalf & Eddy is providing lead design engineering services for the Boston Harbor cleanup project for the Massachusetts Water Resources Authority, which provides wastewater collection and treatment and water supply and distribution for more than 40 communities in the Boston area. As part of the project, the Deer Island wastewater treatment plant is being upgraded and expanded to treat an average flow of 350 mgd and peak flows of 1,270 mgd. This project is one of the largest and most complex in the wastewater treatment industry and is being completed under strict court-mandated deadlines. The design and construction of this project has involved the execution of more than 20 design packages and 41 construction contracts. As lead design engineer, Metcalf & Eddy has overall