Case Study: Oily Wastewater Treatment

Even the largest washing machine manufacturing plant in the world has its own cleaning challenges. Every day thousands of washing machines — more than half of the units sold in North America — come off the line at the Whirlpool Corporation (www.whirlpoolcorp.com) facility in Clyde, Ohio, where the production process generates large amounts of oily wastewater.

The machining and metal finishing processes at the Clyde plant produce oily wastewater that is composed of hundreds of different synthetic and petroleum-based lubricants. Oily waste is segregated from the wastewater stream and separated into a concentrated oily phase and an aqueous phase. The concentrated oil is sold to oil recycling companies, and the aqueous phase is further treated by the plant’s metal hydroxide precipitation process before it is discharged to a sanitary sewer. The plant as a whole produces a daily flow of more than 450,000 gallons of wastewater a day.

A Process In Need of Improvement
"A decade ago, we used to separate and concentrate the oily waste with a crude process of applying acid to break up the oil molecules from the water," says Mark T. DelGarbino, senior environmental engineer, who has 15 years of experience at Whirlpool Corporation, Clyde Division. "However, this process was costly and labor-intensive, and it did not adequately concentrate the oily waste. We were achieving concentrations averaging only 70-75 percent, and it is obviously not good economically or environmentally to be shipping off 30 percent water. We realized that we needed a process that could handle the increasingly large volume and diversity of lubricants from our manufacturing processes."

DelGarbino turned to Koch Membrane Systems (www.kochmembrane.com) of Wilmington, Mass., for a solution. "KMS has long been established as a supplier of membrane separation equipment, and we have extensive experience with its RO process that is used in our electrocoat paint operation, which makes deionized water,” says DelGarbino. “With my significant involvement with the paint department and its processes and suppliers, I viewed KMS as a good resource when I began looking for an oil-water separation supplier."

After a competitive testing and bidding process, Whirlpool chose the KMS KONSOLIDATOR 78, a completely self-contained ultrafiltration (UF) system, utilizing FEG PLUS tubular membranes. The FEG PLUS membranes have been used in wastewater treatment for more than 30 years in many industries worldwide.

Ultrafiltration System Reduces Waste
The KONSOLIDATOR system is capable of concentrating wastewater to an extremely high concentration factor, dramatically reducing the volume of waste. The system is designed with tubular UF membranes that have large flow channels to accommodate streams with significantly high concentrations of solids. To maintain high permeate rates and to minimize the use of cleaning chemicals, the system features a mechanical cleaning process that utilizes spongeballs. Spongeballs are introduced into the cleaning solution and forced under pressure into the tubular membranes. As they pass through the tubes, they wipe the membrane surface clean of accumulated debris.

"The KONSOLIDATOR system has performed very well," says DelGarbino. "I attribute our success to the quality of the system and to the diligence of our technicians. Of the 78 tubes in the KONSOLIDATOR 78, we have only had to replace four of them since we commissioned the system eight years ago."

The Clyde plant achieved its goal of reducing the volume and cost of the concentrated oil that is trucked off-site. The waste oil concentration is now at least 90 percent, which translates into a 60-67 percent reduction in the volume of water in each gallon of concentrated material. In 2005, the UF system processed a total of 3.5 million gallons of oily wastewater, resulting in a total of 103,000 gallons of used oil. While the oil is shipped off-site, the permeate from the KONSOLIDATOR system is sent into the wastewater treatment process before it is discharged to the sewer.

Before the KONSOLIDATOR membrane system was installed, the old acid split process required chemical treatment of batches on a weekly basis. Now, acid is only required occasionally when there is a batch abnormality. The overall reduction in chemical consumption has resulted in significant cost savings for Whirlpool and resulted in a safer working environment for its employees.

Labor costs have also been reduced significantly. The holding tank for the oil-water separation process now fills automatically from the main wastewater collection tank, and the KONSOLIDATOR runs continuously with little need for intervention. Although the entire wastewater treatment operation at the Clyde plant is monitored 24/7, the whole process requires little maintenance.

"With the membrane system, our employees no longer need to continually perform jar testing," says DelGarbino. "They simply monitor the system, and about once a month we perform a cleaning cycle with the spongeball system and KMS KOCHKLEEN membrane cleaning solution to maintain high flux and extend the life of the membranes."

Return on Investment
From a financial standpoint, the return on investment for the KONSOLIDATOR system has exceeded expectations. "Originally, we expected the membrane system to pay for itself by lowering disposal costs with more concentrated sludge and reducing chemical consumption and labor costs," says DelGarbino.

"We did not expect that, in addition to these cost-reductions, we would also create a new and growing revenue stream for Whirlpool. Now that the oil is more concentrated, it is more valuable to the companies that collect it for oil recycling. More concentrated material lowers transportation costs and the amount of processing required, so recycling companies pay us more. During each of the past two years, we sold our used oil for more than $20,000, and we are on track to make even more this year."

With the increasing prices for oil products worldwide, this revenue stream is likely to increase in the future.