If/when a move is made to primarily non-chlorine based treatment at the plant, I expect they would continue to use a final pre-discharge dose of chloramine as an in-pipeline microbiostat until something "better" (i.e., cheaper and tolerable to the masses and governing bodies) comes along. I think the "normal" pre-discharge chloramine dosage acts more as a microbiostat than as a microbiocide, but I haven't tested city water's disinfectant capacity as it exits the tap. That might make a decent project for a school science fair, and it may be that compost tea developers already have explored that. One constraint on treatment options besides the usual disinfection and minimizing of carcinogenic disinfection by-products is the effect that treatment products have on mobilizing metals in the pipeline, especially in older water systems. It has been alleged that chloramine was responsible for the recent high measured lead levels in Washington D.C.'s water system. A further interesting question to me is how/whether chlorine-based disinfectants react/interact with the mix of prescription and otc drug residues in municipal water. Of course, a discussion of potable water treatment wouldn't be complete without mentioning the Chlorine Council's intense and entrenched lobby efforts on behalf of chlorine products.
_________________ In theory, theory and practice are the same; in practice, they aren't -- lament of the synthetic lifestyle.
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