section_path: Treatment
section_name: Treatment
paragraph_text: Treatment
  
  Most water requires some treatment before use; even water from deep wells or springs. The extent of treatment depends on the source of the water. Appropriate technology options in water treatment include both community-scale and household-scale point-of-use (POU) designs. Only a few large urban areas such as Christchurch, New Zealand have access to sufficiently pure water of sufficient volume that no treatment of the raw water is required.
  
  In emergency situations when conventional treatment systems have been compromised, waterborne pathogens may be killed or inactivated by boiling but this requires abundant sources of fuel, and can be very onerous on consumers, especially where it is difficult to store boiled water in sterile conditions. Other techniques, such as filtration, chemical disinfection, and exposure to ultraviolet radiation (including solar UV) have been demonstrated in an array of randomized control trials to significantly reduce levels of water-borne disease among users in low-income countries, but these suffer from the same problems as boiling methods.
  
  Another type of water treatment is called desalination and is used mainly in dry areas with access to large bodies of saltwater.
  
  Publicly available treated water has historically been associated with major increases in life expectancy and improved public health. Water disinfection can greatly reduce the risks of waterborne diseases such as typhoid and cholera. Chlorination is currently the most widely used water disinfection method, although chlorine compounds can react with substances in water and produce disinfection by-products (DBP) that pose problems to human health. Local geological conditions affecting groundwater are determining factors for the presence of various metal ions, often rendering the water " soft " or " hard ".
  
  In the event of contamination of drinking water, government officials typically issue an advisory regarding water consumption. In the case of biological contamination, residents are usually advised to boil their water before consumption or to use bottled water as an alternative. In the case of chemical contamination, residents may be advised to refrain from consuming tap water entirely until the matter is resolved.