The Bigger Picture Of Our Smaller Components

The water purfication cycle

The water purification method does not only include sedimentation, but also consist of two further methods known as coagulation and filtration. These two methods, along with that of sedimentation, forms the basis of the water treatment process and is referred to as clarification.

The process begins by capturing a water source, often available from rain or other methods, and processing these liquids, firstly, via an intake screen. This is done to remove the particles that are large enough to be seen by the eye. The product of this initiating piece of equipment is transferred (via a pumping system) to the first step in the clarification process. It is at this point that coagulants are added to this liquid stream. Due to the sudden addition of the coagulant, an aggitative process must occur to allow for proper mixing of these two liquids. To facilitate this process, the stream then passes through a flash mix tank, and is then passed through a flocculation tank (these processes will be explained next). The product exiting from this tank is the final product from the coagulation process.

The next process to occur in the clarification process is referred to as sedimentation. The now miscible mixture, made possible by the previous process, is allowed to remain a rest. This allows for clean water to be separated from that of “dirty water”. The presence of dirty water is possible due to the previous process. Once most of the original mixture can be separated into clean and dirty water, they are separated. This then brings us to the end of the sedimentation process.

The last process in that of clarification is the filtration process. This process consists of two pieces of equipment, namely a form of filter (such as a rapid dual-media filter) along with a clear well for storage. The clean product that exits the sedimentation process is then fed into the filter. In this piece of machinery the water is further processed to remove the excess sludge from the clean water, which was not removed in the previous step. When separated from the clean water, the dirty backwash water is fed into the same stream as that of the dirty water from the sedimentation tank, while the clean water is transferred to the clear well. In this well, the water is observed and further treatment may be applied if necessary. The water from this well is then transferred along the pipeline via a pumping system. This signifies the end of the filtration process as well as the end of the three-part clarification process.

The clean water that exits is then treated by a disinfectant as the last measure of treatment. The water is then known as purified water, and is then distributed where necessary. The contaminated water that was captured from the sedimentation tank as well as the filter media is sent to a waste disposal system, whereby a small percentage of the water would be regained via more intensive treatment methods.

Coagulation and flocculation

Coagulation and flocculation are two commonly-used terms in the sedimentation industry. These processes form the basis of purification of our most important resources. Coagulation is the accompaning process of which occurs when a coagulant is added in a body of water whereby colloidal suspensions occur. Colloidal particles possess a negative charge and us form non-ideal ionic solutions. Coagulants the solution to this problem as they neutralize the cationic charge as they are positively charged ions.

A metaphor to elaborate "clumping" of similar property products- Flocculation

Flocculation on the other hand, does not at all involve chargers but rather involves the geometry of particles. Flocculation is a process in which polymers are added to a solution in order to clump up the smaller, unstable particles together. Due to this process, larger aggregates of these particles are formed. This ensures that the once smaller particles are able to be removed from his solution and thus produces a higher quality product. As aforementioned, and now reconfirmed, flocculation does not involve any form of neutralization of charge but rather a form of physical process of separation.

A water droplet

This brings us to the end of my first installment on the importance of Sedimentation. I hope that i was able to underline the importance of the processes that allow us to go about our daily lives the way we do. We should be thankful of the modern forms of technology that allow us to be provided with such pure products.

Images are linked to their sources in their description

The End

References:

[1] https://en.wikipedia.org/wiki/Sedimentation

[2] https://www.iwapublishing.com/news/sedimentation-processes
[3] https://www.britannica.com/topic/water-purification/imagesvideos

[4] Unit Operations of Chemical Engineering by McCabe W.L.,Smith J.C. And Harriot P (McGraw-Hill, 7th edition, 2005)

[5] https://en.wikipedia.org/wiki/Mineral_processing

[6] https://en.wikipedia.org/wiki/Water_purification

[7] https://www.sswm.info/content/coagulation-flocculation

[8] Coulson and Richardson's Chemical Engineering Vol. 2, Oxford, Butterworth-Heinemann by Richardson, J. F., Harker, J. H., Backhurst, J. R., & Coulson, J. M. (2002).

[9] https://www.multotec.com/content/mineral-processing

[10] http://www.slideshare.net/SyedTanveer3/mineral-processing34661757