Challenge

Marathon Norco Aerospace located in Waco, Texas is one of the few manufacturers of rechargeable, nickel cadmium batteries for the aerospace industry.  One of the production problems associated with the manufacture of rechargeable, nickel cadmium batteries is the use of a number of heavy metals.  Two of the metals which can be problematic when it comes to waste disposal are cadmium and chromium.

The amount of heavy metal waste generated at the Waco facility categorized the plant as a "significant hazardous waste generator," which created costly off-site hazardous waste disposal and extensive record keeping and documentation. Since 1972, the plant has used a diatomaceous filter system to reduce the volume and concentrate heavy metals in the waste. The plant's hazardous waste production required transport from the plant of over 100,000 pounds per year.

Solution

In 2006, the plant's out-dated, operator intensive and costly process was replaced with a state of the art microfiltration and filter press system from Siemens Water Technologies. Siemens Water Technologies designed a complete wastewater treatment system consisting of metals precipitation, microfiltration, filter press dewatering and pH adjustment of the clarified effluent prior to introduction to the city sewer system. 

Results

• The microfiltration system is producing effluent with a cadmium and chromium monthly average of less than permitted levels.
• Reduced volume of waste by using a filter press is estimated to only being 30,000 pounds per year. This will lower the plant's categorization of being a hazardous waste generator to below "significant."  The re-categorization also reduces the amount of report generation required. 
• The new wastewater treatment system fit within the old system's footprint.

Download the complete project profile
Microfiltration System Reduces Heavy Metal Waste by Two-Thirds (PDF)