Peracetic Acid as a Wastewater Disinfectant

Wastewater treatment consists of two basic steps: removing debris and sediments and removing microbes. The first step in wastewater treatment is to use filters and settling for debris and sediment removal, and the second step is to use either radiation or the introduction of disinfectants such as chlorine or peracetic acid to sterilize the microbes.

History

• In 1950, according to the "Journal of Food Engineering," F.P. Greenspan and P.H. Margulies patented peracetic acid. Their principal purpose for developing the chemical was to sanitize produce, because chlorine had exhibited limited capabilities in this regard. The use of peracetic acid has continually widened since that time, specifically into the field of wastewater treatment. Many public utilities are now replacing disinfectants, such as chlorine, with peracetic acid.

Significance

• The reason Greenspan and Margulies felt the need to develop a new disinfectant was because chlorine, the predominant sterilizing agent of that time, had proven insufficient in certain areas, such as the cleaning of produce. Though other disinfectants such as sodium hypochlorite are also effective, they are not environmentally friendly. Peracetic acid, though, decomposes into nontoxic chemicals that do not harm humans or the environment. This is particularly important for wastewater treatment, because the whole purpose of the process is to remove toxins, impurities and microbes from wastewater that can harm plants, animals, and people after the public utilities release it back into the general water supply.

Definition

• Peracetic acid is defined as the combination of acetic acid (CH3COOH) and hydrogen peroxide (H2O2). This combination results in the chemical designation C2H4O3.

Use

• Water purification services and plumbers frequently use peracetic acid because it is both effective and safe. According to Lenntech, "It can be applied during water purification as a disinfectant and for plumbing disinfection. Peracetic acid is suitable for cooling tower water disinfection; it effectively prevents bio film formation and controls Legionella bacteria." Applied to wastewater management, peracetic acid kills the bacteria that remain after the system has performed the bulk of its duties. Though the removal of sludge and chemical contaminants is vital to wastewater treatment, it is insufficient if there are still harmful microbes in the water.

Danger

• Not only is peracetic acid generally safe to humans and the environment in its pure form, but it also poses a minimal long-term chemical threat. This is because contact with water will cause it to deteriorate into its constituent parts--hydrogen peroxide and acetic acid--and then split into the more basic components of water, hydrogen and carbon dioxide. Thus, since peracetic acid remains chemically intact in water for only a short period, public utilities can use it widely as a wastewater disinfectant without fearing long-term negative effects.