Chlorine is currently the choice for treatment of wastewater. However, apprehensions exist about chlorine both before treatment and following treatment. Since chlorine is highly toxic, fear for public safety is high should chlorine accidentally be released from a treatment plant. Also, there are concerns for the environment receiving the treated wastewater, because of the disinfection by-products and residual chlorine products. Several methods have been developed to deal with the toxicity of chlorine, but are either not as effective as chlorine or too cost prohibitive.
Peracetic acid, or PAA, has shown promise as an effective disinfectant for wastewater. PAA is a strong oxidant and a broad spectrum antimicrobial agent, aiding in the control of bacteria, fungi, and viruses. PAA works on the microbial cells by diffusing through the cell membranes and causing an irreversible breakdown of the enzyme system within the cell [1]. Peracetic acid also appears to work on the DNA of the microbial cells [1]. Previous studies using PAA have demonstrated the ability of the compound to reduce the coliform levels to the required limits associated with permits granted to the treatment plants [2,3]. In fact, PAA has been demonstrated to have similar effectiveness as compared to chlorine dioxide and sodium hypochlorite [1].
At Mississippi State University, we are
investigating the use of PAA in both bench scale tests and in a pilot study. Several
variables will be recorded to determine the efficacy of PAA on the disinfection
of the wastewater. Two concentrations, 2 mg/L and 4 mg/L, are being
investigated to determine the necessary dose to reach the permit levels
required. A contact time of 45 minutes, the time necessary for the
chlorination process to reach completion at the WWTP, will be employed. The
fecal coliform level will be determined before and after treatment, along with
the chemical oxygen demand (COD), total suspended solids (TSS), dissolved
oxygen (DO), and ammonium-nitrogen (NH3-N). These values as compared
with published values from other wastewater disinfection methods, including but
not limited to chlorination, ozonation, UV-treatment, and bromination, will be
presented. A cost comparison between PAA and other common wastewater
disinfection methods will also be presented.
[1] A. Bushini, P. Carboni, M. Furlini, P. Poli, C. Rossi. Mutagenesis, 19, 157, 2004.
[2] S. Stampi, G. De Luca, F. Zanetti. Journal of Applied Microbiology, 91, 833, 2001.
[3] M. Wagner, D. Brumelis, R. Gehr. Water and Environment Research, 74, 33, 2002.