What are the sources of water treatment



The Water treatment serves to adapt raw water to the requirements of drinking water and industrial water use. Water treatment essentially comprises two groups of treatment:

  • Removal of substances from the water (e.g. cleaning, sterilization, iron removal, softening, desalination)
  • Addition of substances and setting of parameters of the water (e.g. dosage, setting of pH value, dissolved ions and conductivity)

There are three basic procedural routes, namely:

  • mechanical processing (e.g. rakes, sieves, filters)
  • physical processing (e.g. aeration, atomization, sedimentation, flotation, vacuum process, thermal effects)
  • chemical processing (e.g. oxidation, disinfection, flocculation, ion exchange, activated carbon (adsorption), osmosis)

These processes are also used in various combinations, depending on the nature of the raw water and the intended use.

Usage

Which methods are used depends on the requirements of the user.

Technical waters (Power plants (feed water), chemical processes, pharmaceuticals) often require a very extensive change in the water properties, e.g. B. by desalination, demineralized water, reverse osmosis, special dosages, degassing and much more. m.
When setting Drinking water the legal and normative requirements (drinking water ordinance, DIN 2000) and the requirements of the distribution network are decisive. Drinking water can be preset by mixing water from different sources in order to achieve a more uniform quality (e.g. mixture of bank filtrate and reservoir water).
Bath water in public outdoor and indoor swimming pools is prepared in accordance with DIN 19643. Flocculation, filtration and chlorine disinfection are the standard procedures.

Treatment is often necessary when water of different properties is mixed. The pH value in the mixed water is often shifted in such a way that the calcite dissolving capacity, i.e. the capacity of the water to dissolve calcium carbonate, becomes impermissibly high (the limit value for the calcite dissolving capacity is 5 mg / L according to the Drinking Water Ordinance). This ability to dissolve calcium carbonate is often referred to as "aggressiveness", more precisely "lime aggressiveness" of the water.

The treatment of groundwater from an adequately protected aquifer is usually less complex than that of spring or surface water. The most frequently used methods for treating groundwater are deacidification, iron removal and manganese removal. Chlorination of the groundwater is only necessary if it is contaminated by atrophogenic germs. Chlorination should always be a temporary process. For the treatment of surface water, on the other hand, more complex processes are usually used. These are often ozonation, flocculation with subsequent sedimentation or filtration and activated carbon filtration to eliminate absorbable pollutants. A final disinfection is mandatory.

Procedure

Mechanical, chemical and biological processes are used for water treatment. The chemical water treatment is divided into the 4 groups flocculation, precipitation, oxidation and ion exchange.

process Plant component purpose
 
SievingRake, drum screen, microscreen Removal of larger solids and floating matter
sedimentation Sand trap, sedimentation basin Removal of small floating matter, sand, flocculated suspended matter
FiltrationFilter, sand filter Removal of suspended matter (particles) including Fe and Mn
Flotation Flotation tank Removal of fine dirt particles by blowing in air
Flocculation Flocculation basin Removal of colloidal substances and fine dirt particles by adding flocculants (discharge of the particles) and adjusting the pH value. Can also be combined with a filtration (flocculation filtration).
precipitation Precipitation basin or precipitation filtration Conversion of dissolved substances into undissolved substances and subsequent sedimentation or flocculation.
oxidation Ventilation systems and gravel filters Removal of dissolved iron and manganese ions (iron removal / manganese removal). The oxidized iron and manganese are deposited on the gravel and are removed again by backwashing the filter.
Ion exchange z. B. Demineralization
adsorptionActivated carbon filter Accumulation of z. B. adsorbable halogenated hydrocarbon compounds (AOX) or dyes
Deacidification Deacidification system Removal of aggressive carbon dioxide. Used to avoid corrosion in the pipe network.
softening Water softener Distance of approx2+ and Mg2+
Desalination Desalination plant Removal of salts e.g. B. for the treatment of seawater for drinking water and for irrigation
Strip Stripping pool Removal by blowing in air / gases. In this way, dissolved water constituents are converted into the gaseous phase in accordance with the vapor pressure and thus removed from the water.
cooling Cooling towers, cooling ponds, heat exchangers, etc. Reduction of the temperature in order to meet the requirements of subsequent processes or uses.
Biochemical process Example: denitrification Exploitation of biochemical processes. In denitrification, the nitrate content of polluted raw water is reduced either by adding carbon in the subsoil or in a reactor.
disinfection Special basin, addition to the pipe network Disinfection by adding chlorine, ozone or UV radiation
Special treatment Special basin for contaminated sewage. Special treatment of wastewater that is contaminated with initially unknown substances or living beings. Examples: Untreated wastewater from electroplating plants or roundworms.


Drinking water treatment

The main tasks and procedures are:

  • Particle removal: flocculation, slow filtration, rapid filtration, membrane filtration
  • Disinfection: chlorination, chlorine dioxide treatment, UV radiation
  • Removal of organic substances: flocculation, adsorption, degassing
  • Deacidification / stabilization: lime-carbonic acid equilibrium, filtration over calcium carbonate / half-burnt dolomite, degassing, dosing
  • Iron removal and manganese removal: filtering processes and underground processes
  • Softening: fast and slow carbonation, ion exchange, nanofiltration

See also

  • Water hardness
  • Water treatment plant
  • Water treatment in the swimming pool
  • biological water treatment in the swimming pond
  • Herbal sewage treatment plant (for cleaning the wastewater)
  • Sewage treatment plant
  • Skimmer

Category: Process engineering