Aluminum Anodizer Implements Zero Liquid Discharge
Success of water minimization reuse at Bonnell Aluminum in Georgia after implementing zero liquid discharge facility for aluminum anodizers.
Bonnell Aluminum is an aluminum extrusion and anodizing operation in Newnan, Georgia. Prior to 2005, wastewater from the operation was treated with conventional chemical precipitation consisting of neutralization, flocculation and clarification. Effluent was discharged into a zero-flow stream and toxicity tests indicated that salts in the effluent could be harmful to water organisms. Bonnell evaluated methods to reduce the toxicity—later deciding to treat and reuse the effluent.
The company encountered many challenges when implementing one of the first zero liquid discharge (ZLD) facilities for aluminum anodizers, which led to 10 years of successful ZLD facility operation. Key results of the operation were:
Investing in a holistic approach for pollution prevention, water conservation and wastewater treatment and reuse;
Changing the wet process to reduce the water usage and reduce the advanced wastewater treatment system;
- A project environmentally, rather than economically, justified;
- 85 percent reduction in city water use;
- Savings of $230,000 per year in city water purchases;
- Maintenance of a high-quality aluminum product with water reuse;
- And reductions in the National Pollutant Discharge Elimination System (NPDES) permit requirements.
Reasons for Changes and Challenges
In 2000, biotesting of Bonnell’s NPDES outfall consistently indicated toxicity to water organisms in the zero-flow stream that received the company’s treated wastewater. The high dissolved solids level in the wastewater (primarily sodium sulfate) was the suspected primary toxin. The NPDES permit was due for renewal and something had to be done about the toxicity of the treated wastewater.
Some of the challenges the company faced included an extremely high flow of wastewater (just under half a million gallons per day), high levels of dissolved solids in treated water, varying compositions of wastewater into treatment, high production demands and the need for a cost-effective solution due to business conditions. The strategy selected dealt with each challenge.