Challenge

The company was discharging its effluent to the city’s wastewater treatment plant, paying sewer access charges of $1.5 million a year.  As part of its long-term cost control plan, Rahr decided to install a 1-million-gallon-per-day (MGD) wastewater treatment plant next to its malting facility, so it could discharge directly into the Minnesota River.

Solution

The OMNIFLO® Sequencing Batch Reactor (SBR) process was the cost saving wastewater treatment process they were looking for.  Rahr Malting worked with our representatives at VESSCO, Inc., Bolton & Menk Engineers and Rice Contracting to design and install a system that would treat 1.0 MGD of influent and reduce their BOD from 850 mg/L to the 12 mg/L specified in the Minnesota Pollution Control Agency (MPCA) permit.  The system incorporates an OMNIFLO® SBR and a Gravisand® filtration system for polishing the SBR effluent.  

The OMNIFLO® SBR is unique in its ability to handle influent flows and a wide range of organic loads and industrial pollutants.  The down flow Gravisand® filtration system is designed to reduce suspended solids, turbidity, and remove phosphorous and algae.

Results

This application was ideal for an sequencing batch reactor given the high variations in flow and waste strength.  The system was designed so that expansion requirements would only involve adding additional reactor basins, which further allows the client to reduce treatment costs in the future. 

• The plant was placed on-line in May 1999, and upon start-up met the 500,000 gallons per day flow rate specified by the MPCA permit. 
• It has consistently met the specifications, with effluent BOD below the 12mg/L limit. 
• In March of 2000, Rahr Malting accepted an award from the MPCA for complying with all permit requirements since the system was started up.

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