Hastelloy for Bleach Applications

[PollyB]

We have found black globs in the bleach tank, (not UV protected). It is used for floccing iron out of our oil-and-gas-field, produced brine (1.2% Cl). Metal digestion analysis shows 0.35 Ni and 0.6% Cr in the bleach downstream of the hastelloy tubing. We have replaced 2 leaking check valves downstream of the holding tank to the brine and rinsed the bleach tan and still the black globs persist. It has been over 100oF for many weeks and as high as 115oF. The top of the 100 gal poly tank is starting to deform since the clean-out. Also, the bleach has lost chlorides, from 15% to 10%. Any Idea, the causes? Should I test for MIC and/or black mold, other other tests. Please tie this to the: 330-129082 thread. Thank-you most kindly.