EAST Process Increases Capacity and Performance at the Sanitary District of Hammond

摘要

This paper discusses how the Sanitary District of Hammond (HSD) increased both its hydraulic and loading capacities by operating its activated sludge facility using an “enhanced activated sludge treatment” process named EAST (patent pending). This paper also discusses the added benefits of improved nutrient removal and reduced biosolids yield from this unique approach. During the past five years the hydraulic loading capacity has increased 50 percent while the ability to handle shock loads has more than doubled. Ammonia removal has consistently exceeded 90 percent while effluent phosphorus levels were reduced to below one part per million. Biosolids yield has dropped by more than one-third. Control practices, implementation costs and the role of process automation are also discussed. Historically, operation of the Hammond treatment plant was complicated by high-strength industrial wastes. Despite an approved pretreatment program, the plant frequently experienced shock loading, foaming, and occasional bulking as a result of influent loading. Efforts to control these upsets by adjusting wasting rates, return rates, mixed liquor inventories, and chemical addition met limited success. The POTW could not consistently achieve desired effluent quality at the design flow of 48 MGD. These difficulties ceased in 1995 when HSD began operating the Kraus process and subsequently improved performance by operating its treatment facility in various modifications to this process. Digested sludge is used to buffer the secondary treatment process and to control the sludge volume index (SVI) within close limits typically ranging from 45 to 65 milliliters per gram of activated sludge. HSD continues to operate in this mode, and while heavy industrial loads continue, the plant has experienced no major process upsets. Operating data shows increased capacity and improved performance for removing solids, chemical oxygen demand (COD), and nutrients. Hydraulic capacity has dramatically increased from 48 MGD to 72 MGD without the construction of expansion facilities. CSO discharge has diminished with the increased hydraulic capacity. Unit costs have decreased since the biosolids yield has reduced by nearly one-third.