Our set up employs four filters in total: 3 filters that 'filter' stuff out of the water and one which zaps the water with UV radiation killing anything that made it through the first two filters.
This is a a VU-FLOW filter, which contains a reusable 100 micron filter. This filter takes out all the big stuff (a technical term used in the water filtering industry), so that the next two filters do not get plugged up too fast.
This is a 30 micron filter. It employs a GE Household water filtration unit, with a 30 micron filter in it. This filter takes out anything larger than about 30 microns so as not to plug up the next filter in the chain. By the way I do not necessarily use GE brand filters as the pricing is fairly competitive amount manufacturers and they all fill each others units.
Her we use a 5 micron carbon activated filter. As you can guess it takes out stuff bigger than 5 microns. But it also has the function of taking out nasty flavours in the water. It uses the same GE filter body as the previous filter.
This filter doesn't filter it kills stuff in the water. It employs a high dose of UV radiation to kill stuff in the water. The UV source, a special light, needs to be replaced every year to ensure the high dose of radiation is maintained. This is the most expensive part -- each new light source is about $90.
After 4 filters the water is very kill and essentially disinfected. Tests have shown zero counts of evil bacteria.
If you wish to know more about each of the above filters check out the previous posts list below or the supplier links embedded above.
creating clean water: uv filters
creating clean water: ge household filter