Got Milk? Got Wastewater Too! Treatment of Dairy Processing Wastewater

A major dairy processing operation owned and operated by the Michigan Milk Producers Association (MMPA) located in central lower Michigan was required to design and construct a process wastewater treatment plant within a 14 month period. The system is sized to treat up to 0.5 MGD of dairy processing wastewater at a biochemical oxygen demand (BOD) concentration up to 1,846 mg/L. Effluent from the treatment process is discharged to a relatively small receiving stream. The State of Michigan included very restrictive discharge criteria in the NPDES permit issued to MMPA for the new treatment process including a seasonal phosphorus limitation of 0.1 mg/L. Historical wastewater characteristics along with milk processing data from the plant were used to establish the treatment process basis of design. The treatment process was required to accommodate variable loadings due to seasonal and market fluctuations in the amount of milk received at the plant throughout the year. The treatment system incorporates preliminary equalization, activated sludge treatment using sequencing batch reactors (SBR), and secondary equalization prior to tertiary filtration. Selection, sizing, and procurement of the major treatment process equipment, prior to completion of the final design, was utilized to meet the aggressive schedule. This paper discusses the history of treatment alternatives used at the site, challenges involved in sizing a treatment system to accommodate a highly variable waste while meeting stringent discharge requirements, completing design and construction within an aggressive timeline, regulatory agency negotiations, and treatment system performance since start-up in early 2002.