Showing category "Coagulation & Filtration" (Show all posts)

Pool Managers - Do You Know How Your Filters Actually Work?

Posted by poolplantcourses.com on Thursday, June 23, 2016, In : Coagulation & Filtration 


Filtration is an important element of effective pool water treatment. The basic principle is that the untreated water is passed through a filtering medium (such as a bed of sand). The water is able to pass through the gaps between the grains of sand (called ‘pores’), but anything larger than the pore size is trapped within the filtering medium.

Pool Water Clarity
A reduction in the clarity of the pool water is a risk to pool users. It is essential that bathers are able to assess the depth o...

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Straining

Posted by poolplantcourses.org on Monday, December 19, 2011, In : Coagulation & Filtration 
Straining is one of the processes taking place during filtration and is perhaps, the one most pool operators will be familiar with. The process involves dirty water passing through the filter media (usually sand) and particles of pollution becoming trapped in the small gaps (pores) between the grains of sand because they are too large to pass through.

Take a look at the picture (click to enlarge). In swimming pool filters, the size of the sand grains is usually 0.5 - 1.0mm. This results in a p...
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Filtration Rate

Posted by poolplantcourses.org on Sunday, December 18, 2011, In : Coagulation & Filtration 
The filtration rate is the rate (in metres per hour) at which the pool water moves down through the filter during normal operation. It is not to be confused with the circulation rate, which is the rate (in cubic metres per hour) at which water is moving through the circulation system.

The filtration rate is calculated by dividing the circulation rate by the surface area of the filter. For example:

Circulation Rate: 100 cubic meres per hour
Filter Surface Area: 5.72 metres squared
Filtration Rate:...
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Sedimentation

Posted by poolplantcourses.org on Saturday, December 17, 2011, In : Coagulation & Filtration 
Sedimentation is one of the processes that is taking place during filtration, the other two being straining and adsorption. Fine particulate matter settles on the upward-facing surfaces of the sand grains. The process of sedimentation can remove finer particles of pollution than straining. As the amount of sediment increases, the amount of space in between sand grains (pores) decreases. This will cause the velocity of water through the filter to increase. Further sedimentation can then no lon...
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Adsorption

Posted by poolplantcourses.org on Saturday, December 17, 2011, In : Coagulation & Filtration 
Adsorption is one of the processes taking place during filtration, the other two being straining and sedimentation. It is not to be confused with absorption. With adsorption, very small particles of pollution adhere to the surface of the sand grains. This process is promoted by electrostatic charges within the particles (similar to a balloon 'sticking' to a wall). Once particles begin to adhere to the sand grains, a sticky coating builds up, which promotes further adherence of particles onto ...
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Coagulation

Posted by poolplantcourses.org on Saturday, December 17, 2011, In : Coagulation & Filtration 
Coagulation is an important process in the swimming pool water treatment process. It helps to remove very small particles from the pool water. In a conventional swimming pool sand filter, the size of the gaps between the sand grains (pores) are around 70 microns. As the filter begins to trap particles, the size of the pores decreases. This is known as 'filter ripening'. When the filter is fully ripened, it will be capable of trapping particles the size of around 5 - 10 microns. The size of cr...
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