Are Your Household Items Making Wastewater Treatment Less Effective?

Recently, we posted an article that discussed the removal of pharmaceuticals and phosphorus in the treatment process. After running the article, a respected certified operator and personal friend of mine, shared her experience with treating wastes containing Triclosan. It was such an interesting story, that I wanted to share it with our readers, as well. I have learned during my tenure in this industry that we (the regulators), as well as the operators, can learn valuable information from sharing stories like this with one another.

Many years ago (somewhere between the death of dinosaurs and the birth of cell phones), I operated a 3 MGD conventional aeration wastewater treatment plant.  This particular plant was designed to treat the organic (oils, fats, glycerin, polymer and synthetics) and inorganic (acids, caustics, dyes, carbonates, etc.) wastes from a factory producing personal care products and over-the-counter pharmaceuticals.

The plant influent was highly variable:  a batch soap-making process might flush caustic with a pH of 11 into the collection system for one hour, with the next hour’s influent containing detergent scrap (very high MBAS), a slug of alcohol-based mint flavoring from toothpaste production and a short burst of acid cleaning solution with a pH of 3.

An equalization basin prior to the treatment train helped smooth out this variability, and our plant did an excellent job of treating these waste streams to meet our NPDES discharge requirements for an outfall into the Ohio River. 

I wanted to share our experience with treating wastes containing Triclosan.  Triclosan is an antimicrobial additive increasingly used in toothpaste, soap, garbage bags and other plastic items, body washes, etc.  Products advertised as “antimicrobial” are likely to contain Triclosan or similar organic compounds.

The FDA’s comments on Triclosan can be found at this link:  My plant was treating the wastewater from the production of Colgate Total toothpaste (mentioned in this article as the only validated use for Triclosan in consumer products).

The process of getting a new product approved by the FDA takes years.  Our plant began making small trial batches of toothpaste with Triclosan for study purposes over five years before the eventual approval and consumer sale of this product.  After the very first trial batch was made, plant technicians washed out the mixing vessel. This sent a small amount of Triclosan-containing material into the sewer system. We had a significant die-off of microorganisms in our aeration basin.  It was immediately apparent that the production of this particular product was going to cause problems for the wastewater treatment plant.  (This was a mixing vessel containing less than 500 pounds of toothpaste, being flushed into a plant operating at around 1.5 MGD at the time – and the concentration of Triclosan in the product was less than 1 percent by weight).

Our wastewater treatment issues began to impact the production schedule. For example, we found that two toothpaste batches could not be washed down in the same day.  This amount of Triclosan would exceed the plant’s capacity to maintain an adequate microorganism population.  It was imperative to find a solution that would allow us to ramp up to full scale production of this product without killing all of the bugs in the treatment plant.

As with so many other things in life, we found that TIME was the best solution.  A half-million gallon oil storage tank had been constructed during the oil crisis of the 1970s. This tank was empty, and we began to valve all wastewater containing Triclosan into that tank and feed the material into the plant influent in a constant stream at low concentrations.  We used time to accomplish the following:

1.       The Triclosan would begin to degrade slightly in the storage tank and lose some of its antimicrobial activity.
2.       We began operating as an extended aeration plant, which increased our removal effectiveness.
3.       By maintaining a constant feed rate of this material, our microorganisms became acclimatized to the Triclosan.  They developed some resistance to the antimicrobial effects and became more efficient at using the Triclosan for food and degrading it in the aeration basin.  We effectively created our own strain of Triclosan-resistant microorganisms, and eventually we could treat higher concentrations of Triclosan-containing material without impacting the population in the aeration basin. 

Most wastewater treatment plants do not have the luxury of pre-storage to “age out” anti-microbial chemicals.  However, with the increasing use of antimicrobials in all sorts of products, it is important for wastewater systems to recognize the potential impact of these chemicals on treatment and the difficulty in achieving removal .  The following link describes a study in Minnesota on the amount of Triclosan accumulating in fresh-water streams due to consumer use of Triclosan.

If you are interested, here is a summary of the treatment scheme and chemicals fed at this particular plant.  This plant had a 1-million gallon equalization basin, followed by coagulation with lime and settling in a clarifier (very similar to a softening operation in water treatment).  Effluent from this clarifier entered a basin for pH adjustment (sulfuric acid) and a very low feed of ferrous sulfate (we found that the ferrous sulfate significantly improved MBAS (surfactant) removal).  The pH-adjusted water entered the aeration basins and then to a final clarifier. Due to the nature of our influent, we had to supplement the aeration basins with nitrogen (bags of urea) to provide the correct balance of nutrients.

As you can see, Triclosan is in many of our household products. We use products and dispose of waste on a daily basis and never give consideration to how that waste will affect the treatment processes that our operators have to deal with every day. It takes skilled professionals to deal with these issues and to maintain effective treatment.  I would like to give a special thank you to Ruth Lancaster for sharing her experience treating Triclosan with us.


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