The water sample I tested was cloudy with bacterial organisms; most likely more concentrated then any thing one would encounter in the real world short of sewer/septic water. The single dose of the Steri-Pen did not achieve bacterial sterilization (it did reduce the number of organism significantly) and a second dose was required.

Keep in mind, that water from a real world situation may have turbidity due to organics, silt or other non-bacterial causes. The Steri-Pen does not remove any chemical contamination. My main reasons and intended use of the Steri-Pen was for drinking water obtained in rural regions of Ecuador, (wells, tap) not streams, ponds, etc. If you were looking to obtain drinkable water from stream, ponds, etc., I would look to a general filter capable of removing chemicals and gross materials, followed with the Steri-Pen or MRS MIOX for microbial (bacterial, viral and parasitic) destruction.

As to contaminated water on the rim/lip of the container, the Steri-Pen will not kill organisms in this area. However, keep in mind that the bacterial contamination of these surfaces may not be significant. Most healthy people (this does not apply if you are immuno-compromised in any way or the very young/old) can tolerate a number of organisms without becoming sick. Each type of organism requires an infective dose/exposure dose before the individual’s immune system is overcome and illness results. This can range from a few hundred organisms to millions. The normal healthy adult has billions of normal bacterial in their GI tract; these organisms not only prevent disease-producing organisms from “setting up shop”, but also produce vitamins necessary for life. That is why it is suggested many times to supplement your diet with active-culture yogurts or Lactobacillus spp. tablets when taking antibiotics or traveling.

Pete