One of the fundamental steps in the treatment of water and wastewater that all professionals in the field should be aware of and comprehend is filtration. What is it, then? Which kinds are there? And how does it happen in a wastewater treatment plant or water treatment plant?
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Meaning
The technique of removing solid particles from a liquid or gaseous fluid by using a filter media that lets the fluid flow through while holding onto the solid particles is called filtration.
It might entail the application of a chemical, biological, or physical barrier. Processes including straining, flocculation, sedimentation, and surface capture are used to remove particles.
The following are basic requirements: a fluid with suspended particles; a filter media (thin or thick barriers); a driving force to make the fluid to flow; and a filter that retains the fluid, holds the filter medium, and allows force to be applied.
How Does the Water Industry Use It?
The purpose of filtering in the water sector is to produce clear water. Though it has use in industrial manufacturing, power plants, food and beverage production facilities, mining, and other heavy-duty applications, its main usage are in storm water, wastewater, and drinking water.
The concentration of bacteria, viruses, fungus, algae, suspended particles, parasites, and other chemical and biological pollutants can be eliminated or decreased via water filtration.
Water cannot be filtered unless a driving force is applied to the filter medium. This force can be generated by gravity, centrifugation, applying pressure to the fluid above the filter, or other processes that use pumps, valves, and pipes to generate sufficient pressure to force the water through the filter.
History
Evidence suggests that it was utilized in the production of wines, brews, and dyes prior to the industrial revolution.
Simple water filtration techniques are depicted in literature and artwork from about 6000 years ago. Most notably, water purification techniques were suggested in ancient Greek and Sanskrit texts.
“Impure water should be purified by being boiled over a fire, or heated in the sun or by dipping a heated iron into it and then allowed to cool, or it may be purified by filtration through sand and coarse gravel,” according to these texts, which characterize early water treatment (Jadhav, Aasawari, 2014).
What are the many kinds?
Strainers, precoat filters, slow sand filters, membrane filters, quick gravity and pressure filters, and granular media filters are among the several kinds of water filters.
Straining and strainers
A very basic technique called straining involves pouring water through a piece of fabric to remove part of the suspended solids and silt, which also kills certain bacteria.
Gravity
Using gravity to draw liquid through a filter is a technique known as gravity filtration. This kind of filtering, which includes sedimentation, flocculation, straining, and interception, takes place via beds of granular media.
The membrane
Membrane filters make use of microfiltration and ultrafiltration, which can be useful in getting rid of germs and/or serve as a pre-treatment before reverse osmosis or nanofiltration are required.
Media
Water is filtered using media filtration systems using a specified filter material, such as:
sand filters
activated carbon in granular form;
cloth, whether woven or not; and
metal screens.
Pressure
A steel pressure vessel houses the pressure filters. The filtered water is collected via perforated pipes or a steel plate with nozzles, and the wash water and air scour are distributed.
The significance of water filtration
Determining the quality of water based just on appearance is nearly impossible. To test for contamination levels, several methods have been developed, including physical, chemical, and biological investigations. Among the often examined indicators to ascertain the degree of pollution and water quality are levels of both organic and inorganic pollutants.
Before it is used by the final consumer, tap water is frequently filtered at a water purification plant. However, officials evaluate the water quality immediately following filtration, prior to the water entering municipal feed pipes, and the findings are typically higher than what is needed. However, the length of the feed lines and their antiquity are yet unknown.
Filtered water can get contaminated by everything it comes into contact with throughout its lengthy journey through the pipes, which are sometimes decades old. As was the case with lead pipes in Flint, Michigan Crisis, and Chicago, old pipes may spread germs, viruses, and other pathogens. The chance of being exposed to dangerous pollutants rises if water is not filtered.
For example, there is proof that human health might suffer when exposed to per- and polyfluoroalkyl substances (PFAS). According to the U.S. EPA, PFAS can build up in the body over time if consumed by people or animals. Humans who are exposed may have negative health impacts include cancer, thyroid hormone imbalance, and a compromised immune system.