Non oxidizing Biocide causing TOC spikes at water treatment facility.

[flatuseng]

We ran into something strange at a customer site recently that hasn't happened until the last year. We inject quats into our cooling water system at our customer site. Coincidentally the Water Treatment Facility on this site gets their supply water from this same system. The water treatment facility just went through a recent upgrade in which they switched from an old system to now having one involving a ultra filtration unit that eventually supplies their RO unit. The only thing that they no longer have in their system is a set of dual media filters.Now everytime we treat our system with quats they get large TOC spikes for about the first 12 hours then they taper down into spec eventually. Our customer seems convinced that it is the ethanol solvent in the quat, although that doesn't make much since due to the fact that the TOC tapers off during the whole 24 to 72 hour treatment. From my perspective I think they may be getting hit with large slugs of biologics for the first 12 hours causing the TOC spikes and thats why it tapers off eventually, mainly because everythings dead.May be a simplistic way of looking at things, but it fits. Just wanted to know if anyone else had experienced anything similar to this?

 

[unclesyd]

i believe you are correct in your assumption in what happening, a lot of dead plants. When we used Chromates for the CTW there was no spike but when we went to others we started getting them. We had a similar problem with our sand and Ronningen-Petter filters after a shock treatment. We would automatically increase the backwash cycle prior to every shock treatment. I have never heard any problem in our water plant as we use straight shot well water.
One thing that goes along with this is we see much lower counts in the cooler months so the water people back off on the treatment and we go back to summer levels. Not only do we see this by analysis we see it in the test loops on the corrosion test coupons.