I would say that jsoong hit the nail on the head. It would appear that chloramine is added to your drinking water. AFAIK, they do not add NH3 directly to the drinking water.
Here is your 2006 water report:
http://www.atlantawatershed.org/pdf/WQR2006.pdf
It does not mention the addition of chloramine? But under the "Disinfection Byproducts", it informs you of what chloramine is and what it does.
http://www.nsf.org/consumer/drinking_water/disinfection_byproducts.asp?program=WaterTre
That would lead me to believe that it is added.
Here is also a list of what is tested:
http://www.nsf.org/consumer/drinking_water/dw_contaminant_protocols.asp?program=WaterTre
chloramine is one of them.
BTW, I cannot find any mention of receiving water from Lake Lanier. All of the processing plants get your drinking water from the Chattahoochee River.
This is from the water report:
"Sources of Your Water
Each day, the Atlanta water system provides
approximately 120 million gallons of treated drinking
water for nearly 1 million residents in the metropolitan
Atlanta area. All the water processed is surface water from
the Chattahoochee River.
The raw water intake for the Chattahoochee and
Hemphill Water Treatment Plants is located on the
Chattahoochee River. The Chattahoochee Plant receives
the water directly from the river. The Hemphill Plant
processes raw water that has been pumped from the river
to a reservoir. These two plants supply about 75% of
Atlanta’s drinking water. The remaining water is supplied
by the Atlanta-Fulton County Water Treatment Plant, which
also processes water from the Chattahoochee River. This
plant supplies treated (finished) water to the northern area
of our distribution system."
You can also find the EPA's website using google, or the like, if you would like more info on what can and cannot be added to drinking water along with the federal limits for each.
Also beware of what you read on these boards before you research it yourself. Although I don't believe most posters would intentionally give you bad information, some suggestions could contribute to problems one may be having.
Though I wouldn't have included the "these boards" in your comment, that is true of all things on the internet. DO NOT take a single peice of advice for the truth! Research many different sites/forums/threads before taking action.
Randy
P.S. Prime (dechlor product) is highly recommended by MANY menbers of this site. It will make the NH3/NH4 non-toxic, but still allow it to be used by your bacteria. IE binding NH3/NH4 and making is unusable is not a good thing. Your bacteria still needs it to feed itself.