WASTEWATER TREATMENT AT GENERAL MOTORS --
Todd Williams, senior project engineer for water and wastewater treatment at General Motors, isn’t afraid to challenge the status quo. But before he could start pushing for changes in GM’s water-intnsive automotive production processes, he had to spend time in the paint shops learning exactly how those processes worked.
He also needed to build trust with the paint engineers. “You need to know enough about the process to say, ‘That’s not right. Let’s work through this,’” he says. “I want to make sure the process is robust.”
Williams will be discussing strategies for conserving water and saving money at the 2017 Environmental Leader Conference in June. We recently caught up with him to learn more about how to build the business case for water conservation and reuse projects.
What is the main challenge organizations face in conserving water?
One of the biggest challenges is a general perception that water is free. At GM, we continually have to communicate the cost of water. It’s not our most expensive utility, but water costs seem like they’re going to continue to increase at a rate significantly above inflation. We’re looking at doing things that 10 or 20 years ago wouldn’t have made the cut.
In the automotive industry, the biggest water user is our paint departments. Preparing, washing, coating, providing the right heating, ventilation, humidity levels for paint — that drives a significant amount of water usage. I spend a lot of time with the paint process engineers. We’ve developed counter-flowing rinses and built that into the process.
How do counter-flowing rinses work?
There are three rinsing processes: clean and rinse, conversion coat and rinse, electro-coat and rinse. We take the metal part, a ‘body in white’ — the body panels, the frame, the doors. That goes through a cleaning process then a conversion-coating process, usually a first-level corrosion inhibition. We rinse it again. We go through a dip paint called an electro-coat, basically electro-plating paint on the surfaces. It goes through another rinse.
If you took a car body, dipped it into one big tank, and then went onto the next process, the amount of water you’d have to put in one tank to keep that rinse water clean would be an awful lot. Instead of having one tank, we have two or three. You continuously add water to your cleanest tank, and you let that overflow to the previous tanks, which are dirtier and dirtier. When you go from a one-stage to a two-stage counterflow rinse, you reduce the water usage required to get the car clean by about 90%. Our new ones are actually three stages.
What steps did you take to make the business case for changing the rinsing process?
First, we’ve got to make sure we have a way to measure the water. In some of our older facilities, there are not a lot of water meters, even instantaneous-reading water meters for spray rinses. There is usually a formula you can set on the new processes: I want 30 gallons a minute to go into this rinse system. You can increase or decrease it. We put water meters in key positions where the operators can see how much water they’re using day to day and make sure it’s correct.
If I see problems, I always put that in dollars and cents to the engineers and the management. For one of our new paint shops, they wanted to add city water to a rinse. There was no water meter. They said, ‘I’m only adding a little bit.’ I went back and put on a portable ultrasonic flow meter. It was 55 gallons a minute, which is filling up a drum every minute 24-7. This pipe runs three shifts, five days a week, 48 weeks a year, approximately. It came out to roughly $300,000 per year. That got their attention.
How did you work to change this?
You want to include all the costs associated with using the excess water to build a business case. A lot of this is education. I’m not a paint process engineer, I am a mechanical engineer and have a fair bit of process engineering knowledge and experience. I spent a lot of time the last couple years looking at the rinse systems. I had interns work with me. We did studies on the rinse systems in one of the paint shops here. I got to know enough about the process to challenge the status quo. And it’s starting to bear some fruit in making sure we get our water usage in line.
Related to water reduction and sustainability, what approach is GM taking to stormwater?
An example that’s still in implementation is our Detroit-Hamtramck assembly plant. That’s where we make the Chevy Volt, Impalas, and other vehicles. We have a stormwater reuse project where we collaborated with the City of Detroit Water and Sewage Department. We were paying large fees for discharging stormwater to the city sewer system. It was based on the acreage of the site. We worked with them to say, if we put in more storage, can we go to a volume discharge fee instead? We could have enough storage to hold a 100-year rain event on site. Then we’d discharge it at a time when they can handle it to help reduce any combined sewer overflows.
Our existing two ponds are approximately 10 million gallons each. Our third pond we built is about 25 million gallons. When we built the pond, we looked at can we use this water onsite? So we actually pump it back to our powerhouse, where our first step is to run it through refurbished multimedia filters. After filtering, we take that water and use it in our cooling towers. We were still going to have a lot of water to discharge, though. We thought, we can make high purity water for ourselves. After going through the multimedia filter, we run it through carbon filters to prepare it for reverse osmosis. Last year we reused about 50 million gallons of stormwater in our cooling towers and our paint process. This year we hope to reuse between 100 million and 200 million gallons.
The last piece of this project is we purchase steam from a company offsite called Detroit Renewable Power. They have a use for high purity water in their boiler system. We already had a pipe to them about a mile and a half away so we worked with them to get a credit. We’re going to be testing it soon.
What advice do you have for others as they approach water management?
Know how much water you’re using. Once you know how many gallons you use, then you can put together a business case. You also need management support. Part of that is to have water reduction goals, and then drive those down to the facility level. Each one of our manufacturing facilities has a scorecard with their water budget on there. If they don’t meet the water budget, it actually affects the plant manager’s bonus. It keeps everyone’s eye on the ‘water’ ball.
Todd Williams will be speaking at the Environmental Leader Conference in Denver June 5-7, 2017. His track, New Strategies for Stormwater Management, starts at 3 pm on June 6.
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