Hire a qualified consultant to design the system. Be aware of possible contamination sources, like barnyard runoff or discharge pipes, when locating the intake pipe. Place the pipe in the deepest, most remote 'clean water' possible. Avoid areas of high algae growth. Both steps are necessary to remove or kill all bacteria, viruses, and parasites and make the water safe to drink.
Filtration removes soil particles and plant material that can interfere with disinfection.
It also removes parasites that are not killed by disinfection. A one-micron filter is required for complete removal, because some parasites can be as small as two microns. A single one-micron filter is likely to clog as it removes sediment and algae. As a result, home systems commonly use a series of cartridge filters, with each filter removing smaller particles. Another option is a rapid sand filter followed by two cartridge filters.