Speaker Defines the Process of Treating Drinking Water

Keion Moradi
El Vaquero Staff Writer

Dr. Gordon Purser of the University of Tulsa addressed the topic “What’s in My Drinking Water: How water Chlorination Produces Tastes, Odors and Toxic Compounds” Tuesday in the CM lecture hall, one in a series of talks in the Science Lecture Series.

Out of the four methods for primary water disinfection, most of the Los Angeles basin uses chlorine gas. The typical water treatment procedure begins with a pre-oxidation process, Purser said, with the goal to “take the water and start breaking down things that are in the water that we don’t want there.”

Then alum and carbon are added, sticking to the surface of these unwanted organisms. The water is moved to a clarifier and sediments sink to the bottom.

After letting the water settle, the top is skimmed and the primary disinfectant (chlorine in our case) is added. The water then flows in to a filter bed removing any lingering particles. A chlorine residual is added to prevent the growth of other organisms before the water is moved to a distribution system.

“Unfortunately, adding chlorine does create problems with taste and odor,” said Purser. Water treatment involving the use of chlorine dates back to the 1930s, when residents began complaining about foul tasting water.

“You have a choice, Purser said. “You can drink water that doesn’t taste very good or you can drink water that will kill you.”

In 1971, chloroform was identified in the air space above chlorinated water samples. Purser described this event as the driving force for all research funding. Frequent exposure has been known to induce harmful physiological effects, including liver disease.

In 1990, a comprehensive study identified another 22 disinfection byproducts (DBPs) as a result of chlorination. DBPs are mainly a result of humic and fulvic acids produced from the chemical reaction produced between chlorine and byproducts of decaying vegetation.

Purser defined the current research goals as identifying which of the oxidation products of humic acids lead to DBPs, determining the reactivity with chlorination, and understanding why compounds are found in drinking water by studying the chemical reactions.

Members of the audience asked about the safety of tap water in the Los Angeles area, as well as bottled water. Purser recommended using a filter in order to “remove organic chlorinated species” if it is of personal concern. When buying bottled water, consumers were urged to buy water either “distilled or produced via reverse osmosis.”