BACKGROUND

When an amendment to Korean national law prohibited waste discharge to seawater, sludge waste disposal costs increased significantly for one Korean automaker. The plant’s paint shop, which manages its own sub wastewater treatment facility, was seeing the impact of these cost overruns on their operations budget.

In addition, Environmental, Social and Governance (ESG) considerations have become a management priority in the automotive market. Waste reduction could contribute favorably to the company’s environmental goals and support their continued investment in the company’s future. Overall, the plant sought ways to reduce sludge disposal, expense, overall chemical spend for wastewater treatment and operating time.

The incumbent supplier used commodity chemicals, which are known to be inefficient at reducing sludge and use a significant amount of chemistry albeit at a low cost per kilogram. A 60 m³/hr (15,850 gallons/hr) wastewater stream came from the paint shop to a reaction tank. The wastewater was dosed with commodity pH-adjustment chemistries, then floc was created by adding a flocculant before flowing to the dissolved air flotation (DAF) unit. Here, the sludge and water were separated before flowing to an aeration tank for biological treatment. Finally, the wastewater flowed to the sedimentation tank before release to the final wastewater treatment facility.

RESULTS

The updated programme lessened the amount of pH adjustment and flocculant required, which reduced the overall chemical spend by more than USD $29,000 per year. Employee safety was also improved through a reduction in chemical handling, inventory management and personnel exposure. Further, the new programme reduced sludge volumes by 528 metric tons, saving the customer more than USD $90,800 in disposal costs. The reduced amount of sludge also saved labour time at the centrifuge process.