What is the best method for bacterial disinfection of drinking water and why and effective method for killing microorganisms in contaminated water?
Boiling is a very simple method of water disinfection. Heating water to a high temperature, 100°C, kills most of the pathogenic organisms, particularly viruses and bacteria causing waterborne diseases. In order for boiling to be most effective, the water must boil for at least 20 minutes. Disinfection with chlorine dioxide has a high effectiveness in killing bacteria; Combination filtration and disinfection has a very high effectiveness in removing and killing bacteria when used with iodine, chlorine, or chlorine dioxide and an absolute less than or equal to 0.3 micron filter.
Boiling is very unpractical and expensive due to the energy use. It should only be used as an emergency procedure.
The choice of disinfection depend a lot on the water quality and considerations of by-products.
If you need to name one as the best it is hard to argue against ultraviolet radiation. It is the almost always the cheapest method and it leaves no chemical residue in the water. I suggest the reason it is not the dominantly used method worldwide is that many water distributions systems are poorly constructed and therefor there need to be a disinfectant residual (like chlorine, chloramine or chlorine dioxide) in the water until the tap to protect from reinfection or regrowth of bacteria.
FUN FACT: In Denmark less than 1% of water works apply disinfection as we use groundwater and good hygiene at the waterworks.
UV certainly can be effective - requires control of particulates and rigorous maintenance of lights and surfaces. Maybe not so great for "contaminated" water. As Henrik noted, it leaves no residual so systems include a background bacteria and biofilm.
Think in an older report, EPA estimated costs were about equal for large water treatment systems with UV more cost effective with smaller systems.
Chlorination is the process of adding chlorine to drinking water to kill parasites, bacteria, and viruses. Different processes can be used to achieve safe levels of chlorine in drinking water. Disinfection with iodine or chlorine has a high effectiveness in killing viruses; Disinfection with chlorine dioxide has a high effectiveness in killing viruses; Disinfection has a high effectiveness in killing viruses when used with iodine, chlorine, or chlorine dioxide. Boiling or heating water is the most widely used and effective method to kill disease-causing germs, including viruses, bacteria, and parasites.The most common method of disinfection is through the addition of chlorine to drinking water supplies. Chlorine effectively kills waterborne bacteria and viruses and continues to keep the water safe as it travels from the treatment plant to the consumer's tap. Boiling can be used as a pathogen reduction method that should kill all pathogens. Water should be brought to a rolling boil for 1 minute. At altitudes greater than 6,500 feet (approximately 2,000 meters), you should boil water for 3 minutes. Common sources of fecal matter in our environment include sewers, septic systems, and animal wastes. Pathogens from these sources can get into our drinking water. Testing drinking water for coliform bacteria is a simple way to find out if there may be pathogens in the water.
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