Description of the Video:
This video demonstrates how to filter water by using a plastic water bottle, charcoal from a fire, grass leaves, and sand. It's not the best quality, and he seems somewhat disorganized but he manages to accomplish what he sets out to do. It's basically a small gravity feed filter.
First he cuts the bottle bottom off, and screws the cap on. He then makes a small hole in the cap. This will let the water through.
Filling some of the bottle with grass, green grass in this case, a layer of charcoal, semi crushed, and then another layer of grass then charcoal again. He also puts a layer of sand as well which he then packs in tight to fill all the air gaps that might have been left.
This method won't get rid of some of the smaller bacteria that still might be harmful, but it will clean it very well from particulate matter.
He then puts a small amount of water into the bottle filter and puts it over another bottle to catch the water dripping from the hole that was made in the cap.
The process was slow and looks like after about 30 minutes (his estimation) there is about half a cup of drinkable, yellow colored water, which he then drinks. Seems to me like this would take a long time to make enough drinkable water to sustain oneself in the long term.
At the end of the video, about 12 minutes in, he starts to explain how to make a filter that will also kill off some of the bacteria by using plants such as mint and pine needles. He fills a plastic water bottle with dirty water and stuffs some crushed mint leaves and pine needles in order to have the volatile oils kill some bacteria.
The main method of purification in this method is really the sun he explains. Let the closed bottle sit in the sun for 4 hours and then it will be safe to drink, although he doesn't demonstrate it.
I can't say that I would use this method unless it was really necessary. I was just putting it up to show the basics of how easy it is to make a simple gravity fed sand/charcoal water filter in the field.
What he is explaining to us here is called the SODIS method, that's a term created by putting together the words: SOlar DISinfection. He states that by putting the clear bottle in the sun, that the UV rays will kill off the harmful bacteria and viruses. This is true but it should be done for six hours in direct sun to be absolutely sure, unless there are some modifications made to the setup. The more cloudy the water, he more sun exposure it will need to be disinfected properly.
I can't say that I like drinking water that has been heated up in a plastic bottle as the chemicals do leach out into the water, especially with an aged bottle. But given the choice in a survival situation, it would be much better than drinking water contaminated with live harmful organisms. So the basic setup, using a homemade filter in addition to the SODIS method would produce safe drinking water, although it would take time to make any large quantities.