There was in fact mixing of sewage with drinking water, not to mention food preparation, because the sewage was being deposited here, there and everywhere before the toilet block was opened, and it was being tracked back to the campsites, including where people were washing, cooking and eating. That's how people started spreading the intestinal disorder around, and that's how you get epidemics.
Where we were in KN people were firing off flares, and not looking out for where they were going to land either. And some people were firing roman candles AT tents and through campsites -- it seems likely that one of these days this is going to start a fire in a campsite and people will get hurt.