[Senator Bedfellow]

Near a large University somewhere East of Austin, during an inspection of the interior of an elevated storage tank belonging to a municpality, it was found one of the interior walkways was furnished with a small sofa and several cases of empty beer cans.

I conclude that I'm happy that I didn't attend this university. Mainly for the "ick" factor, if not heath concerns ;)

Anyway, you could probably engineer a biological agent that would survive chlorinated water systems - you'd probably start with a chlorine resistant strain of E. coli or Legionalla, or protozoans like Giardia or Cryptosporidium, and tweak them to increase their effects on humans. But again, this is beyond the ability of some guy working out of his basement - while it's probably doable, we're talking about large investments of time, money, equipment, and expertise to pull it off. Comparatively speaking, biological agents are much, much harder to produce than chemical agents. Hell, even nuclear weapons are probably somewhat easier to produce, since you at least have a sort of blueprint to work from with nukes.

[rock58seg]

There does already exist a chlorine resistant strain of pathogen..It encases itself with a chlorine resistant shell. (for want of a better description) Google "oocysts". They are however easily controlled with either ultraviolet or reverse osmosis and sometimes even just filtering... One of the reasons a lot of systems are going to hybrid systems of disinfection.