Peracetic Acid for Disinfection

Feb. 23, 2021

How peracetic acid is replacing chlorine in water & wastewater treatment

About the author:

Hannah Rouillard is the lake, pond and municipal brand manager for Biosafe Systems. Rouillard can be reached at [email protected].

They say scent is the sense with the strongest ties to memory. The smell of chlorine reminds me of swimming lessons at the YMCA. I remember the taste of pennies, my curls drying brittle on the car ride home, and the number one rule when swimming: do not open your eyes underwater. But I did, of course, because that is the only way a 6-year-old can win Marco Polo. 

I can recall with perfect clarity the blurry burn in my eyes after a swimming lesson, and blinking did not help. My eyes could not be quenched, my skin felt tight, my baby blonde hair took on a green hue in daylight and especially under the locker room fluorescent lights. But, my swim coach, my parents, and the janitor told me the pungent smell and stinging in my eyes was a powerful chemical working to keep the whole place clean and safe. 

Chlorine’s Upbringing

Since its first use in 1905 to decontaminate Britain’s drinking water and halt the typhoid epidemic, chlorination has proven to be effective, otherwise society would not have been leaning on it so heavily for more than a century. But chlorine, and all its potency, flooded into all manner of water treatment outside potable water disinfection including irrigation water systems, community reservoirs and municipal wastewater. It is being used in broad strokes throughout water treatment and then haphazardly discharged into the environment. 

Historically, chlorine was the smell of clean for most of the 20th century. The world has come a long way since then and learned how toxic it is to aquatic life, and how it disrupts vital ecosystems, the livelihood of coastal industries, soil health and irrigation in agribusiness, and even communal surface waters. 

When chlorine oxidizes organic matter, the reaction creates hazardous disinfection by-products (DBPs), including trihalomethanes (THMs) and haloacetic acids (HAAs) that can contaminate surface waters communities use in everyday life. These toxic by-products make the water unsafe to reintroduce to the environment. While it boasts cost-effective disinfection, it often requires the extra, expensive step of dechlorination after treating water. The long-term effects of discharging dechlorinated compounds into the environment are unknown. As a result, the U.S. EPA implemented stringent  restrictions on acceptable levels of chlorine residuals and DBPs in municipal wastewater effluent waters. Less detrimental alternatives exist now, and it is time for the industry to take advantage of these new sustainable developments in water treatment, and one such option is peroxyacetic acid, also known as peracetic acid or PAA. 

How PAA Disinfects Water

Several case studies have been conducted and consistently illustrate PAA’s efficacy in removing human health pathogens from water, neutralizing sulfur-based odor compounds without harmful residuals. PAA is a disinfectant with chemical compounds utilized for years in operations in Europe, but it has only recently gained popularity in the U.S. 

BioSafe Systems has spent more than 20 years converting chlorine users to PAA advocates and continues to gain momentum in a positive and sustainable direction. 

All commercially available PAA-based products contain an equilibrium mixture of hydrogen peroxide, water and acetic acid. When PAA decomposes in water, two oxidizing powerhouses, hydrogen peroxyl (HO₂) and hydroxyl (OH) are formed and commence cell lysis. Disinfection occurs when the bacterial cell wall disintegrates after contact with PAA’s free radicals. These compounds remain stable in the water allowing them to target pathogens and bacteria without breaking apart or reverting to their precursor makeup. 

PAA for Wastewater Treatment

PAA blends with wastewater the same way chlorine does, permitting a seamless transition from one chemical to another. PAA does not require extra equipment or expenses, making it an easy and economical choice for wastewater treatment operations. 

The effective disinfection of wastewater has been tried, tested and proven successful all over the U.S. from New Jersey to Kentucky, and even in California, which has some of the strictest environmental regulatory statutes. PAA products are not hindered by the turbidity or pH levels of wastewater, which makes them more effective in turbulent, opaque water than UV light. 

UV needs water clarity upfront for the disinfecting light to penetrate, and in lab tests, visual clarity in water is noticeable moments after PAA is introduced to the sample. 

Ozone is another alternative to chlorine but requires complex equipment, and the chemical is a highly corrosive and reactive compound. When PAA is used to treat wastewater, its chemistry oxidizes on contact then breaks down into completely non-toxic components. 


Looking Towards the Future

Attention has been pulled from noxious chlorine, and the water treatment industry is turning its focus towards alternatives such as PAA. This chemistry is the advancement in scientific solutions for which many water treatment workers have been waiting. 

PAA has begun to save businesses and municipalities time, money and stress when keeping up with compliance regulations. Successful, broad-spectrum disinfection in a short amount of time, with easy implementation and absence of by-products is what has made PAA a desirable and progressive option for both water and wastewater treatment. 

About the Author

Hannah Rouillard

Image courtesy Institute of Chemical Research of Catalonia (ICIQ).
All images courtesy of Ecosorb.