In ancient times, civilizations and society in general formed around bodies of water. Whether that water source was a creek, lake, river or ocean it was vital to the survival of the people inhabiting it. Very early on, it was discovered that this water had to be treated somehow, not necessarily to prevent acquiring certain illnesses, however, but more for appearance so it seemed.
Around the year 4,000 B.C., we discover the first documented occurrences of water treatment. They included charcoal filtering, straining, and boiling amongst others. While these treatments were mostly aesthetic in order to reduce cloudiness of water, it began a long timeline of municipal water treatment.
The Egyptians refined water treatment processes as early as 1,500 B.C. where they used a chemical called Alum in order to settle particulates out of water. After a large jump in time, filtration emerged in the 1700s, and in the 1800s: sand filtration.
In the mid to late 1800s, scientists such as Dr. John Snow and Louis Pasteur discovered that pathogens and germs invisible to the naked eye were responsible for the spread of disease. After this discovery, municipalities began to turn towards disinfectants to help stop the spread of diseases such as typhoid, dysentery, and cholera.
Emergence of Disinfectants
In 1908, chlorine was used in the United States for the first time in Jersey City, New Jersey. In 1914, the first federal regulations concerning the quality of drinking water were set. These standards were set by the U.S. Public Health Service and only applied to drinking water for interstate transportation systems. Further, these standards only limited bacteria that were capable of causing contagious diseases.
These standards were revised and expanded upon 3 times: 1925, 1946, and 1962. The revisions in 1962 were the most extensive, which limited the content of 28 substances in public drinking water. Industrial and agricultural advances brought man-made chemicals into the argument. The push for new regulation brought about the Safe Drinking Water Act of 1974, now enforced by the United States Environmental Protection Agency (EPA). Due to the enactment of this legislation, the number of water systems being treated has dramatically increased.
Techniques for Disinfection
Many different molecules are used for water system disinfection, whereas chlorine is most widely used for disinfection of drinking water, both traditionally and presently. In the 1970s and 80s, ozone emerged as another option for municipalities. This came about due to chlorine resistant pathogens that could cause illnesses such as hepatitis, gastroenteritis, Legionnaire’s Disease, and cryptosporidiosis. This level awareness set the stage for additional treatment options, even more sophisticated methods to treat potentially contaminated water.
Chlorine Dioxide (ClO₂) was first used at a spa in Ostend, Belgium. In 1992, it was estimated that 700-900 public water systems used chlorine dioxide as a disinfectant. Use of chlorine dioxide offers many advantages over use of over chlorine, most notably that it does not create trihalomethanes and haloacetic acids or other carcinogenic byproducts. Further, because ClO₂ does not kill pathogens by chlorination–but instead by oxidation–pathogens cannot build up any type of resistance to the oxidation solution.
The Elimination of Bio-Slime
Another advantage which ClO₂ presents is a superior ability to eliminate and eradicate bio-slime. Bio-slime can build up inside of the water treatment distribution systems, and whereas in a system that uses chlorine or ozone for contamination control, this slime will prevail. However, since ClO₂ exists as a neutrally charged gas dissolved in water, with continue use for contamination control, it can move through protective coverings of bio-slime and kill underlying pathogens as well as attack certain proteins where the bio-slime adheres within. With the aforementioned chemical advantages, ClO₂ can effectively remove bio-slime whilst also preventing its re-emergence.