A Pilot-Scale Study of Peracetic Acid and Ultraviolet Light for Wastewater Disinfection

Peracetic acid (PAA) is a potential alternative disinfectant for wastewater. While laboratory studies have shown promising results on PAA’s disinfection performance, knowledge gaps remain regarding scale-up and the potential additive effect of adding UV treatment after PAA treatment. A 4-week pilot study was conducted to investigate PAA disinfection of secondary and tertiary (granular media filtered) effluents. By varying PAA concentrations (2, 3, 4 and 6 mg l-1) and sampling location along the pilot reactor (theoretical contact times 2.2, 6.7 and 22.5 min), a wide range of C·t values 4.4 – 135 mg min l-1 was investigated. Additionally, a low-pressure UV lamp (30 mJ cm-2) was installed to determine if UV treatment augmented PAA disinfection. Disinfection performance was assessed based on the inactivation of three fecal indicator bacteria (FIB) (fecal coliforms, E. coli, and Enterococcus spp.) and a virus (somatic coliphage). PAA inactivation was greatest for fecal coliforms/E. coli, followed by Enterococcus spp., and then somatic coliphage. Results showed that increasing C·t resulted in an increase in the log reduction of FIB and coliphage in both secondary and tertiary effluents. The relative effectiveness of increasing PAA concentration versus contact time to improving inactivation varied among the microorganisms. Sequential PAA-UV treatment (PAA 45 – 135 mg min l-1, UV 30 mJ cm¬-2) achieved higher inactivation than PAA alone for somatic coliphage in secondary effluent, and for fecal coliforms, E. coli and somatic coliphage in tertiary effluent. PAA performance did not exhibit a dependence on any of the water quality parameters routinely monitored, including turbidity.