If you live in a city, it is easy to take tap water for granted. With a single turn of a faucet knob, you have access to clean, clear water, ready to drink. Ensuring that water is free from contaminants, however, is a multistage process. Municipal water treatment plants use a variety of technologies to purify your tap water and keep it safe.
Contaminants
In nature, water is full of substances that can alter its taste and odor and even make you sick. Dirt and suspended solids, large particles that can make water murky and cloudy, are common. Bacteria and parasites like cryptosporidium and giardia make bodies of water their home, and can cause serious health problems if they make it into your system. The purification process removes these substances from your tap water.
Sedimentation
First, treatment plants pump water into large reservoirs, where it stands for long periods to allow solids and other heavy contaminants to fall out of solution as sediment. A positively charged chemical called a flocculant can speed up this process by attracting the negatively charged particles, forming clumps that settle out faster. Once this process is complete, the clearer water at the top of the reservoir is ready to filter.
Filtration
The filtration process removes smaller particles that survived the sedimentation process and strips out organic compounds that can affect the taste and odor of your tap water. Generally, industrial filtration systems utilize clean gravel and sand as a pre-filter, stripping out most contaminants before running the water through activated carbon. The large surface area of activated carbon, coupled with its positive charge, attracts many different types of contaminants and traps them against its surface.
Disinfection
Filtration cannot remove microscopic biological contaminants. Bacteria and viruses can easily make their way through any filtration media, which is why treatment facilities take an additional precaution against these living microorganisms. Most water treatment plants in America use chlorine to disinfect the water, as it not only kills biological contaminants effectively, but its presence in the water protects it from further growth all the way to your tap.
Considerations
Unfortunately, once the water receives its final treatment, it is not always safe. Old or damaged pipes can release minerals or even lead into the water that can cause health problems for your family. If you have concerns about the plumbing in your home, a commercial water purifier or filter can ensure that the water you drink is as safe as possible.
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