Tuesday, October 02, 2012

The Water Treatment Process: Part 1


To really understand why you should conserve water, you should learn about what a treatment plant typically does in order to get it ready for consumption. Private well-water users are usually on their own, and many drink from their wells directly. Moving on...

Depending on where your water comes from, different processes are used to make it safer to drink. The word "safer" was used because nothing is perfect, but that doesn't mean there aren't standards in place. Speaking of, depending on your location, there are usually state, provincial, or federal standards for water quality. One such industry standard is the Ten States Standard, which is used as a reference quite often in designing water treatment plants. In Ontario, Canada, water quality is regulated by the provincial ("state") government.

Now, let's go back to where your water comes from and what needs to be done. The most common water sources are groundwater and surface water. Groundwater is pumped up from the ground using wells, either by a municipality or at a private residence/property. This is usually the cleanest water since the water had to travel through soil a fairly long distance. However, if the aquifer that holds the water underground is too close to the surface or isn't well confined, it may be contaminated. Remember that if rain and water makes its way down, everything else in liquid form, or which can be transported by water (e.g. leachate), can make it down too –  I won’t even touch NAPLs, DNAPLs, or LNAPLs.

Surface water is what you find in lakes, ponds, or the ocean. Everything that runs off the ground is collected in water bodies, and there is no soil medium to do any pre-filtering. Also, the relatively higher availability of oxygen, sunlight, and food generally helps microorganisms thrive. This water source is usually the dirtiest.

There is actually one other water source and that is rain. Instead of letting it run on the ground into an aquifer or lake, it can be collected directly on a catchment surface into a storage area for use. This is relatively clean water as it's had minimal contact with various surfaces, aside from maybe a roof. However, a roof is in itself a very large and contaminated exposed surface. We'll go into this topic in the future since I may have done a major graduate level project on it.

Intuitively, the cleaner the water at the source is, the less that has to be done with it to make it potable (i.e. drinkable). Okay, three paragraphs later and we have the water sources covered.

The main purpose of water treatment is to make water safe enough for consumption with minimal risk to consumers. It's not sterile. A cost-benefit analysis has been done to determine what level of contaminants is "acceptable". Now, don't freak out. In general, what researchers and authorities did was find the highest level for contaminants at which spending more money to remove more produces minimal health benefits. Like it or not, everything does have a dollar value.

What can be found in water?

A lot of stuff. Really. A lot. Remember what you use to wash your hands when they get dirty? Ya, water is the great natural solvent (or something like that). You have "natural" stuff including algae, and pathogens like bacteria, viruses and other microorganisms in water. And then you have your heavy metals, chemicals, pesticides, fertilizers, byproducts of organisms, decomposing organisms, etc. All of this is generally removed through four unit processes in a treatment train.

We'll look at a typical treatment train once I feel like writing about it!

Water Treatment Part II...