Have you attempted to run a culture or a microscopic examination on the purple material? Chlorine can oxidize both organic and inorganic materials. I wouldn't jump to that conclusion without more information.


However, if chlorine solves the plugging problem; is it possible to add a low dose to the water being filtered?

grrun

Do you have wineries operating in your area now? Could be grape yeast/leavings if they are transferring, bottling, etc.

This might help - especially if you can measure hydrogen sulfide in the wastewater.....The purple sulfur bacteria are a group of Proteobacteria capable of photosynthesis, collectively referred to as purple bacteria. They are anaerobic or microaerophilic, and are often found in hot springs or stagnant water. Unlike plants, algae, and cyanobacteria, they do not use water as their reducing agent, and so do not produce oxygen. Instead they use hydrogen sulfide, which is oxidized to produce granules of elemental sulfur. This in turn may be oxidized to form sulfuric acid.

The purple sulfur bacteria are divided into two families, the Chromatiaceae and Ectothiorhodospiraceae, which respectively produce internal and external sulfur granules, and show differences in the structure of their internal membranes. They make up the order Chromatiales, included in the gamma subdivision of the Proteobacteria. The genus Halothiobacillus is also included in the Chromatiales, in its own family, but it is not photosynthetic.

Purple sulfur bacteria are generally found in illuminated anoxic zones of lakes and other aquatic habitats where hydrogen sulfide accumulates and also in "sulfur springs" where geochemically or biologically produced hydrogen sulfide can trigger the formation of blooms of purple sulfur bacteria. Anoxic conditions are required for photosynthesis; these bacteria cannot thrive in oxygenated environments.[1]

Aspergillus is a fungi - it also can appear purple and is a common pollutant in citrus/juice effluent.

Aspregillus will survive in high DO water - but will not handle OH or super oxide anions. Additionally, hydrolase enzymes normally can be dosed and this dissolves the polysaccharide outer cellular membrane.