What are the disadvantages of peracetic acid disinfectant?

Drawbacks of peracetic acid as a disinfectant

Peracetic acid (PAA) is widely used as a disinfectant in wastewater treatment due to its strong antimicrobial properties and rapid degradation. However, it’s not without its downsides. One of the main concerns lies in what happens after it does its job.

When peracetic acid breaks down, it decomposes into acetic acid and oxygen. While this decomposition is relatively environmentally friendly compared to other chemical disinfectants, it introduces a significant issue: increased organic content in the treated effluent. Acetic acid, a byproduct of PAA breakdown, contributes to higher levels of organic matter in the water. This residue, though not highly toxic, serves as a nutrient source for microorganisms.

The presence of acetic acid in the effluent raises the risk of microbial regrowth further down the line. In simple terms, even after disinfection, the leftover organic material can allow bacteria and other microbes to re-establish themselves in distribution systems or receiving waters. This defeats one of the primary goals of disinfection—ensuring long-term microbial safety.

The residual organic load can complicate compliance with discharge regulations. Many environmental standards monitor parameters like chemical oxygen demand (COD) or biochemical oxygen demand (BOD), both of which can be elevated due to acetic acid. Facilities using PAA may need additional treatment steps or dilution strategies to meet regulatory limits.

While peracetic acid remains a valuable tool—especially in settings where chlorine byproducts are a concern, its limitations must be carefully managed. Operators should consider the downstream impact of acetic acid residuals and monitor for potential regrowth and organic buildup. Effective disinfection isn’t just about killing pathogens, it’s about ensuring the water stays safe after treatment, too.