Ultraviolet Light Water Disinfection
UV Filtration systems are used in tandem with other filtration methods as a step that deactivates the DNA of microorganisms, making them unable to reproduce. These prove to be a very worthy addition to your well or cistern system!
For those interested in specifically removing fluoride, please see here
Basics of UV Ray Filtration
Ultraviolet water purification lamps produce UV-C or “germicidal UV,” radiation of much greater intensity than sunlight. Almost all of a UV lamp’s output is concentrated in the 254 nanometers (nm) region in order to take full advantage of the germicidal properties of this wavelength.
How Does UV Disinfection Work?
UV-C light deactivates the DNA of bacteria, viruses and other pathogens, which destroys their ability to multiply and cause disease. As UV light penetrates through the cell wall and cytoplasmic membrane, it causes a molecular rearrangement of the microorganism’s DNA, which prevents it from reproducing. Specifically, UV-C light causes damage to the nucleic acid of microorganisms by forming covalent bonds between certain adjacent bases in the DNA. The formation of such bonds prevent the DNA from being unzipped for replication, and the organism is unable to reproduce. In fact, when the organism tries to replicate, it dies.
Ultraviolet Water Filters Kill the Following Bacteria, Viruses and Cysts
Our UV purifiers generate 30,000 microwatt seconds/cm2 or 30mjoules/cm2 for the required flow rate. Here is a list of some of the numerous bacteria and viruses our UV purifiers kill, with the dosages required to kill them (much lower than what our units generate). You can expect eradication of 99.9% of bacteria, viruses and cysts when the proper flow rate is maintained:
Example of the price of UV bulbs for this purpose
Slow Sand Filtration, explanations, safety, design
Basic information on Slow Sand Filtration
Basics on Designing a Slow Sand Filter
First used in the U.S. in 1872, slow sand filters are the oldest type of municipal water filtration.
Today, they remain a promising filtration method for small systems with low turbidity or algae-
containing source waters. Slow sand filtration does not require pretreatment or extensive operator
control—which can be important for a small system operator with several responsibilities.
A slow sand filter is a sand filter adapted for household use. Please note that although commonly referred to as the BioSand Filter, the BioSand Filter terminology is trademarked to one particular design, and this page encompasses all slow sand filters. The version most widely implemented consists of layers of sand and gravel in a concrete or plastic container approximately 0.9 meters tall and 0.3 meters square. The water level is maintained to 5-6 cm above the sand layer by setting the height of the outlet pipe. This shallow water layer allows a bioactive layer to grow on top of the sand, which contributes to the reduction of disease-causing organisms.
Rainwater harvesting with Sustainable technology: A look at the design, construction and operation of a small scale slow sand water filter. (Building a small slow sand water filter for individual use)
A guide of about 100 pages from the World Health Organization
Another large guide from the Department of Health in Washington state, US.