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Q.When our mass finishing equipment is started after being shut down a week or more, an extreme stench emanates from the entire system. We are almost driven from the plant by the foul odors; sometimes a swarm of flies even rises up from the media! We now spray insecticide over the equipment before starting it, but the stench remains almost unbearable. How can we control this problem? W.D.


A. This is a very timely question with production cutbacks a reality across the industrial landscape. All good industrial compounds—that includes cutting and grinding fluids, washing fluids, hydraulic fluids, and so on—contain some chemistry designed to control the growth of mold, fungus, and bacteria. The quantity of such agents in a compound is determined by various considerations: operators’ safety, environment, tank life expectations and cost. The current problem is that tank life requirements have far exceeded the design parameters.

Your compound supplier should be able to guide you in choosing a chemical treatment that can be applied before a planned shutdown. This can be quite effective, depending on the circumstances.

Just as a back up, I am going to give you a procedure you can follow if you want to try it on your own. Start with a list of all reservoirs, holding tanks, settling tanks, sumps, and machine capacities, including the size of each. Any fluid or system that will be contacted by the operators’ hands, including the media in the vibrator, will be treated to a level of 1,200 ppm with the chemical. Settling tanks and sumps holding effluent to be discharged will be treated to 3,000 ppm (1,200 ppm is about 4.5 mL/gal; and, 3,000 ppm is about 11 mL/gal). When treatment is complete, shut down the system and do not operate it again until production resumes.

The chemical I recommend is hexahydro-1,3,5- Tris(2-hydroxyethyl)— s-triazine. It is sometimes abbreviated to s-triazine. This is a chemical with some handling cautions and should be used responsibly, as you would your garden insecticides and herbicides. Read and heed the label!