Raw Water

Last updated: April 9, 2018

What Does Raw Water Mean?

Raw water is natural water like rainwater, groundwater and water from bodies like lakes and rivers. Water is considered to be raw until it is treated by a potable water treatment process.

Raw water is less expensive than treated water, but carries more risk. In a steam-generating unit, contaminants of raw water may:

  • Corrode metals
  • Form insulating deposits of sediments
  • Scale on heat-transfer surfaces
  • Cause overheating and possible failure of pressurized parts

Corrosionpedia Explains Raw Water

Raw water is water that is taken directly from its source without treatment. It contains one or more of the following significant contaminants in the form of dissolved ions, particles and living organisms:

  • Humic acid and other complex acids resulting from plant decay
  • Minerals, which make water hard
  • Particles of clay and silt
  • Microorganisms such as bacteria, viruses, protozoa and their cysts
  • Dissolved air molecules, especially oxygen
  • Salt, which makes water brackish
  • Industrial or municipal waste

Raw water is purified for a variety of purposes, meeting the requirements of medical/pharmacological, and chemical/industrial applications. Purification methods include:

  • Physical processes like filtration, sedimentation and distillation
  • Biological processes like slow sand filters or biologically active carbon
  • Chemical processes like flocculation and chlorination
  • Electromagnetic radiation such as ultraviolet light

For steam generation, suspended solids are eliminated by settling or filtration. Scale-forming hardness is reduced by chemical treatment to make insoluble precipitates that are removable by filtration, or soluble compounds that do not form scale. Complete purification is obtained by demineralizing treatments or evaporation.

Industrial raw water purification is employed to optimize most water-based industrial processes like heating/cooling/processing, and cleaning/rinsing. The ultimate goal is to reduce operating costs and risks. Improper water treatment can cause serious damage to the process and the final results. Surfaces of pipes and vessels can be affected by corrosion and steam boilers can scale or corrode.


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