Doesn't surprise me.

Mostly because sterility is more a scalar then an absolute. Very few things are ever absolutely sterile and if they ever get to that level they seldom stay that way for long.

Also some consideration has to be given toward the difference between non-sterile and non-infective. A material can be loaded with microbes but as long as those microbes are species that the body can handle and/or do not cause disease then being non-sterile is not a problem.

More on-point, the 'cleaning' of a wound using any particular solution would seem to be at least somewhat more effective the more sterile and less infective it is. Sterile water being at least notionally better than non-sterile water.

But there are at least three other factors that come to mind: First, exactly how much less sterile, or more importantly more infective, was the non-sterile solution. Tap water is not sterile but exactly how much more infective is it? Is the difference between tap water and sterile solution meaningless, or at least less important, on a bacteriological and infective level?

The second thought that comes to mind is: How does time play into this? Would an immediate irrigation with less clean water be better than waiting for more clean water? The answer would seem to be affirmative for the longer haul. You certainly wouldn't wait a week for an IV bag of NS to arrive by mail if the water available was relatively clean.

But would waiting thirty minutes to get to a supply of sterile water be justified? Would it be better to irrigate with potable water immediately and removing the worse of the dirt in the wound now or do you take the time to set up provisions for boiling water? Would it be better to do both? Or is the second rinse just more trauma to the already damaged tissue?

The third thought is that in this, and so many other situations, your going to run into the law of diminishing returns. The difference between raw sewage and safe potable water is pretty big. The difference between: 'Wouldn't use it on a bet' and 'We go with what we got'.

With this in mind it doesn't surprise me that the difference between tap water, presumably pretty clean and chlorinated, boiled water and commercial sterile solution would be pretty small.

The study I would like to see is irrigation with water versus irrigation with soap and water followed by a rinse.