Sewage treatment plants – also called waste water treatment plants – are responsible for cleaning waste water from residential areas with the aid of biological, chemical and mechanical processes. After the waste water has been treated, it can be fed back into circulation or into rivers, brooks or lakes. The transport of the waste water and suspensions within the individual clarification stages is controlled by valves, flaps and gates.
Modern sewage treatment plants work according to the three-stage principle. In the process, the waste water passes through three cleaning stages in which valves are also used to control the transport:
Mechanical pre-cleaning stage
The mechanical pre-cleaning stage is used to trap and separate dirt particles so that they do not block the pumps in the sewage treatment plant. In the subsequent tanks (grit chamber and primary treatment tank), other contaminants are removed at the floor (e.g. sand particles or small stones) or on the surface (e.g. oil or grease).
This stage involves adding microorganisms (bacteria and yeasts) to the waste water and continuously supplying them with air so that they can break down biological impurities.
Chemical cleaning stage
In the third cleaning stage, sewage treatment plants use chemical reactions such as oxidation and precipitation to primarily remove phosphorous from the waste water. This stage is important to prevent any enrichment of the waterways with nutrients.
The removal of sewage sludges is controlled with the aid of various different types of valve. The sludges are transported to digestion tanks or digestion containers designed for this purpose where they are broken down into digester sludge and digester gas under oxygen-free conditions.
Pinch valves can be used in sewage treatment plants and waste water treatment wherever the transport of waste water, sludges and chemical or biological media need to be controlled.
As well as pinch valves, various types of knife gate valves (e.g. unidirectional knife gate valves or bidirectional knife gate valves) are also used to control the waste water.
Pinch valves and knife gate valves can be individually configured for use in sewage treatment plants. Both types of valves can be used in waste water treatment without any problems with abrasion-resistant sleeves (in the case of pinch valves) or with suitable gland packings and soft seals (in the case of knife gate valves).
They can also both be used as control valves for transporting the contaminants removed from the waste water in the different clarification processes. Pinch valves and knife gate valves control all media safely and reliably – whether in the transport of sewage sludge to the digestion tanks or in the removal of digester sludge and digester gas from the digestion tanks.
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