Thanks to modern engineering, humans can recycle the dirtiest, most foul-smelling water into a clear liquid that is safe to drink. If you have ever wondered how this process works, here is a simple description of the basic steps involved.
The first step in industrial wastewater treatment is to bring small contaminants together into larger pieces by a process known as flocculation. Sanitation workers achieve this result by adding chemicals such as aluminum sulfate, ferric sulfate, or sodium aluminate, which cause the dirt to clump together through a chemical reaction.
The larger particles, referred to as floc, become denser than water and subsequently sink to the bottom. This process removes a large amount of contaminants, which are then sequestered in the mud at the bottom of the holding tank or pond. In natural areas, land managers use this process to remove toxins that might poison wildlife.
The water at the top of the tank passes through a series of filters made of charcoal, sand, and gravel. The contaminants trapped by the filters include the following:
- Parasitic microorganisms
- Some larger chemicals
Chemicals too small to be trapped by most filters include polyfluoroalkyl compounds, hormones, and many prescription drugs.
The final step is to kill any harmful microorganisms in the water by adding a disinfectant such as chlorine, chlorine dioxide, or chloramine. While chlorine is not considered good for people in general, it is safe to drink at a level of 4 parts per million. Most municipal water supplies regularly monitor the level of chlorine.
The details may vary between various water treatment plants, but the above four steps are followed for most applications. The next time you turn on your faucet, think about the amazing journey your glass of water has probably taken.