History of Water Treatment
Water has always played a prominent role in human civilization. When people first began settling in one place and growing crops for sustenance, it was invariably near water sources like rivers, lakes, or groundwater springs. Water was needed for drinking, preparing food, bathing, cleaning, irrigating crops, and a variety of other tasks, so it was important to have ready access to this resource. The water sources used for supplying water were not always clean however, and treating drinking water to improve smell, taste, clarity, or to remove disease-causing pathogens has occurred in one form or another throughout recorded history.
Drinking Water Treatment Process
Now that you are familiar with drinking water treatment, let's examine modern methods in greater detail. In general, the treatment of drinking water by municipal water systems involves a few key steps:
The water is mixed to liberate dissolved gases and to suspended particles in the water column.
The materials and particles present in drinking water (clay, organic material, metals, microorganisms) are often quite small and so will not settle out from the water column without assistance. To help the settling process along, "coagulating" compounds are added to the water, and suspended particles "stick" to these compounds and create large and heavy clumps of material.
The water is left undisturbed to allow the heavy clumps of particles and coagulants to settle out.
The water is run through a series of filters which trap and remove particles still remaining in the water column. Typically, beds of sand or charcoal are used to accomplish this task.
The water, now largely free of particles and microorganisms, is treated to destroy any remaining disease-causing pathogens. This is commonly done with chlorination (the same process used to eliminate pathogens in swimming pools), ozone, or ultraviolet radiation. The water is now safe to drink and is sent to pumping stations for distribution to homes and businesses.
Examine in detail the process of drinking water treatment and its relationship to human health with the resources below. Once your review of this material is complete, proceed to the Activity.