REMOVAL OF BOD AND METAL IONS FROM DAIRY PROCESSING WASTEWATER

Abstract

An anaerobic membrane bioreactor (MBR) unit was to design to remove 98% of BOD, COD, and TSS from a dairy wastewater processing stream at an influent flow rate of 500,000 gal/day. The hydraulic retention time of the MBR unit was determined to be 4 hours and the sludge retention time of the MBR unit was determined to be 60 days. Methane produced by the anaerobic process will be recaptured at 67% efficiency and will reused as a heat source in the plant. Metal ions will be removed from the wastewater through electrodialysis and the effluent concentration reaches EPA standards. An evaporation pond to deal with the brine stream from the electrodialysis has been designed with a volume of 4250 m3, a fill time of 41 days and an evaporation time of 37 days. The capital costs associated with the plant design is $11,000,000 with the evaporation pond and $9,000,000 without the evaporation pond. Assuming the filtered water is sold, the breakeven point for the design without the evaporation pond is 50 years. Although target concentrations can be reached with MBR technology, we do not recommend utilizing this design until pilot scale tests can be done.