Water purification

The water treatment is the purposeful change in water quality. Generally it comprises two groups of treatment:

• Removal of substances from the water (eg, cleaning, sterilization, removal of iron and manganese removal, softening, desalination);
• Addition of substances and setting parameters of the water ( eg, dosage adjustment of pH, dissolved ions and conductivity ).

Water treatment is an essential step in the production of drinking water for human consumption ( drinking water supply).

Water treatment processes

The treatment process can be classified as described below:

The following table gives an overview of various treatment processes and their applications.

Areas of application

The most important methods are listed above in tabular form. A plant for the treatment of water is but rarely only a single process but very often several. The required number and type of procedure is determined by:

• The nature and quality of raw water and the dissolved and undissolved constituents
• Usage and requirements for the treated water (pure water )

Raw water: The main raw water suppliers in Central Europe are:

• Groundwater from shallow wells or deep wells
• Bank filtrate from near-surface shallow wells
• Surface water from rivers or lakes and reservoirs

Surface water, and it particularly running water, (flood periods) contains at least temporarily high levels of undissolved particles. Organic contaminants can also be included, although these only occur at low altitude through the legal requirements for direct dischargers of wastewater and treated wastewater for now. In Lake and dam water, however, the content of undissolved material and organic substances is significantly lower.

Groundwater is depending on the type of soil layers from which it is conveyed, often more or less burdened by dissolved iron and manganese compounds and higher levels of free carbon dioxide ( CO2). Are dissolved or colloidal organic compounds, if at all, only in small dimensions available. Near-surface well water, particularly in areas with marshy ground and layers of landfills, but also contain higher concentrations of organic contaminants.

Use of the pure water

Apart from the waste water treatment from, will be discussed here in detail, there are mainly two types for use specifically as:

• Drinking water and
• Water for industry and commerce as well as in agriculture for irrigation, the latter is, however, almost never prepared

The following information for the type of treatment are only examples of some typical and frequent system combinations. In individual cases further and cited also by the different process steps may be necessary to achieve the required quality of pure water. On the other hand, may be sufficient without treatment in some cases the quality of raw water for use.

In the production of drinking water, the legal and normative standards (eg German Drinking Water Ordinance, DIN 2000) and the requirements of the distribution network shall prevail.

A typical treatment plant for surface water as raw water consists of:

• A filter stage for the separation of the undissolved substances, including additional flocculation for the improvement of the cleaning effect of the filter circuit, and a disinfection of the clean water. If the raw water containing too high levels of carbonate, then an additional carbonisation installation may be arranged in front of the filter stage. When using surface water of the filter stage will be preceded by a mechanical pre-treatment with rakes and drum filters or Siebbandanlagen.

With ground water from surface or deep wells a ventilation level for the oxidation and precipitation of iron and Manganoxidhydraten before filtering is often required. Same time, this the oxygen content of the water is increased and simultaneously removes excess Kohlensäuere in an open ventilation. This is important for the pipeline networks of the material iron to reduce corrosion by forming a Kalkrostschutzschicht.

• A special form, the requirements for drinking water directly comparable, is the treatment of swimming pool water. The bath water in public outdoor and indoor swimming pools is treated according to the German DIN 19643 or the Swiss SIA 385/1. Typical process steps for this are the standard methods for flocculation, filtration, and disinfection.

Hot water is used for power plants ( cooling and feed water ), industrial plants, chemical processes, pharmaceuticals, food industry, laundries and v. m. required in large quantities. Often very far-reaching changes in water properties are required. Moreover, in a system different grades are often required to clean water. For example, other demands are made as to the process water to the make-up water for cooling systems almost always.

• Treatment systems for cooling water, in cases where surface water is treated, often consist of a mechanical pre- raking, drum filters or Siebbandanlagen followed by flocculation with filter stage and at high Carbonathärtegehalten, an additional Entcarbonisierungsstufe. In addition, the circulation of water is treated more about dosing with hardness stabilization and anti- corrosion chemicals. If you are using well water as raw water is generally not necessary to a filter stage, if no decarbonization is required.

• Since the requirements are almost always higher on the quality of the process water, a part of the treated water is removed for the cooling systems and purified further as possible. Additional treatment processes such as adsorption for removing org. Impurities, reverse osmosis or ion exchange resins for the partial or full desalination and degasser for the removal of dissolved gases, but are required.