The screen printing process, by definition, creates waste, particularly in the form of inks and the chemicals used to clean them off screens and tools. Some of this waste is hazardous. As awareness of environmental and safety concerns continue to grow, so does the importance of having a plan for properly disposing of it.
This may involve using a commercial industry waste disposal service and/or its proprietary products, your own in-house recycling system or, mostly likely, a combination of the two.
Either way, a sound waste disposal strategy begins with knowing:
- The chemicals you’re using and their potential hazards
- The city, state and other regulations that apply to disposing of these chemicals
- Your waste disposal options and how they comply with applicable laws and how they meet the needs of your operation.
Ink needs to be cleaned off screens, ink paddles and stirring sticks, scoops, buckets, etc. There are various types of screen printing and cleaning chemicals on the market for doing this, some of which are more environmentally friendly and/or recyclable than others.
Factors such as the type and volume of printing you’re doing and performance requirements are key considerations in product choice. It’s also important to be familiar with the MSDS on inks and chemicals. If you opt to use a waste management service, you will need to provide this information to them.
In most cases, for instance, it is necessary to use a product like an ink degrader that will enable the ink to be removed. The problem is that these products only temporarily break up and dilute the ink, so it washes off, rather than truly being “dissolved.”
Then when the tool is rinsed with water, the ink and any other chemicals that have been washed off go down the drain. If this waste water is collected in a tank or container, it re-congeals into sludge.
Basically every shop produces some waste. This is true even if you’re recirculating your chemicals. Therefore, the goal has to be to generate the least amount of waste as possible.
Rules & Regs
There are strict regulations governing hazardous waste disposal. They exist at local and state levels and can vary based on where your shop is located. It is up to you to learn if and how these rules apply to your operation. You are responsible for the chemicals used in your shop from cradle to grave, including their proper disposal.
Some chemicals have a certain flash point, for example. This means the fire marshal or OSHA can come in and require you to dispose of the rags and T-shirts you clean your screens with in a specific container rather than put them in the dumpster because of their potential flammability. It’s smart to use chemicals that have a high flash point.
There also are procedures and products that can minimize waste and disposal issues. If you’re a small shop cleaning only 20 or so screens a day, you may be able to apply a low- or no-flammability screen cleaner using a spray bottle, scrub it with a pad brush, squeegee it off and then wipe the squeegee with a T-shirt.
Afterward, you can water rinse and air dry the shirt. There also are press wipes available with a chemical that will lock ink into a T-shirt and allow it to be run through a dryer for reuse. As long as the shirt/rag meets the flash point, you should be able to throw it in with your regular trash when it’s no longer fit to use.
It’s also about ink management. The more ink that’s left on your screen to be scraped out, the more chemical you’ll use getting it out. This in turn results in a dirtier shirt and more waste is generated. Waste is simply overuse of product, and keeping that in mind can save you on consumables spending at both ends of the process. The problem is magnified in larger operations. This is why a sound disposal strategy is essential.
A waste disposal service, such as Safety Kleen or others, can facilitate compliance. They will haul away liquids and solids that have built up from recirculation and provide you with a manifest letter verifying how your waste is being handled.
Waste containers can be provided by the service or you can buy your own. Again, depending on the rules governing waste disposal in your area, if you’re recirculating your own chemicals and putting the solids that settle into drums, there may be local companies that can take them away.
One of the best ways to minimize the amount of chemical waste is to use an automatic screen cleaning machine and a recirculating chemical system. If your volume doesn’t justify an automatic cleaner, a recirculation system can be purchased separately.
A recirculation system basically functions to minimize waste by decanting used chemicals. Refuse is collected in a container and the solid waste settles to the bottom. The remaining clear liquid chemistry on top is siphoned off. That is then topped off with fresh product for reuse.
You’re not only generating less waste and reducing the amount of chemicals you’re putting down the drain, but because you’re reusing your chemicals, you’re cutting down on your chemical purchases and spending less.
With the Sgreen Chemical Recirculation System, the ink degrader is pumped from a tank with particle separators through a flow-through brush during cleaning in a washout sink. A hose from the drain takes used chemicals and waste ink back to the tank where they are filtered and collected for reuse.
Although perhaps 90 percent of the ink in a screen can be wiped out, you’re also dealing with products like emulsion removers, which can be more difficult to reclaim. Because of this, a water filtration system is probably the best way to go. Such a system safeguards plumbing and minimizes environmental impact, proactively addressing disposal requirements and regulations.
Used in conjunction with proper screen-making and cleaning practices, a water filtration system filters out solids such as tape, raw and solidified ink and cured emulsion. Waste water is caught as it comes out of the sink and sent through a multistep filtration process before it is sent to septic tank—or even laid outside to dry/harden for solid disposal. Once again, much depends on your shop’s location.
The bottom line is to be proactive. Know the agencies impacting your operation and their rules with respect to the products you’re using. Talk to distributors and manufacturers about how they deal with their (larger-scale) waste. A little research and a responsible approach upfront can save you money and a lot of headaches in the long run and position your business for a successful future.
from Ryonet Blog http://blog.screenprinting.com/disposing-hazardous-shop-waste/
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