I have problem with bacteria growing in a nutrient-deprived environment. They can go dormant, but not reproduce. There has to be substrate for growth and replication to occur. Even when bacteria go dormant in pure water (even that poses a problem of hypotonicity, that bacteria better have a capsule or a relly thick cell wall or risk bursting!), it will likely not survive a pH 1-2 in the stomach.
You may have a problem with it in theory, but in reality, it can be a severe problem. That is why many RO systems for human use incorporate a UV to kill bacteria. They do not need to grow fast to be a concern.
From the FDA:
http://www.fda.gov/ICECI/Inspections/InspectionGuides/InspectionTechnicalGuides/ucm072913.htm
Researchers at the Center for Disease Control (CDC) conducted extensive investigations on the bacterial contamination of RO systems used in producing purified water for dialysis (15). They reported: 1. certain naturally occurring Gram- negative bacteria can multiply in relatively pure RO water; 2. thorough periodic disinfection of the entire RO system is essential in producing water with acceptable bacterial counts; 3. stagnant water in pipes down stream of the membrane is the major source of bacteria and endotoxin in the product water; and 4. the efficiency of a membrane in rejecting bacteria is better in continuous operation than in intermittent use.
and
Technical Requirements of a RO System
Several basic technical requirements of a RO system are:
Feed water should be adjusted to proper pH and be prefiltered. The amount of TDS and suspended materials in the feed water after prefiltration should be controlled within the designed limits.
Feed water and product water should be monitored for microbiological quality. The system should be disinfected when microbiological quality levels are exceeded.
All system components should be mechanically cleaned before disinfecting. Appropriate tests should be performed to assure that chemicals used in disinfection are completely removed from the system.
The use of filters or ion-exchangers down stream of RO modules should be avoided.
The RO system should be designed for continuous flow without traps, dead ends and pipe sections which may collect stagnant water.
The chemical and microbial quality of water should be tested at predetermined intervals during a production cycle. In-line conductivity probes should be installed at key points for continuous monitoring of water quality.
The equipment should be qualified and the RO system should be validated periodically, as well as operated and maintained according to manufacturer's instructions so that it can consistently produce water with acceptable quality.