Full scale evaluation of combined sewer overflows disinfection using performic acid in a sea-outfall pipe

Abstract

(2015). Full scale evaluation of combined sewer overflows disinfection using performic acid in a sea-outfall pipe. Chemical Engineering Journal, 270, 133-139. https://doi.org/10.1016Journal, 270, 133-139. https://doi.org/10. /j.cej.2015 AbstractPollution of surface waters with pathogens from combined sewer overflows limits recreational use of surface waters. Large retention basins are a satisfactory solution but they are rarely sufficient for economic or space reasons. Fast disinfection during the overflow is an alternative, but few methods are known and each has problems. This work evaluated for the first time the full-scale disinfection using performic acid by the removal of the two currently regulated indicator bacteria for bathing water quality, E. coli and Enterococcus. Experiments were performed at a sewage bypass through a sea-outfall pipe with a minimum hydraulic retention time of 24 min. The disinfection efficiency in the field was measured by analyzing samples taken before and after the treatment. Samples were also treated with performic acid in the laboratory to measure the disinfection effectiveness and kinetic of degradation of performic acid. Doses of 1-8 ppm of performic acid achieved 1.0-3.5 log removal of E coli and 1.0-2.44 log removal of Enterococcus in the field, but were somewhat higher in laboratory conditions at 1.69-4.38 and 1.0-4.27 log units, respectively. Studies of the degradation of performic acid in collected real samples showed more than 50 % was degraded in 20 min, and mostly degraded by 120 min. Comparison of field and laboratory dosed samples detected that performic acid synthesis didn't start in one event and clogging of the sampler in another event.Overall the tests showed that the treatment was successful but it is indicated that online control could benefit treatments efficiency.

Peracids in water treatment: A critical review

“…However, in a recent comparison study, PFA required a significantly shorter contact time than PAA: 20 and 360 mins, respectively, when a similar dose (2-5 mg/L) was used [136]. PFA was also studied in a fullscale experiment (1-8 mg/L and a contact time of 24 mins), which confirmed that the EU bathing water microbial quality was possible to be reached with the method after taking into account dilution to the receiving water body [137]. Tondera et al [35] used PFA (at 12-24 mg/L, and with a 10-minute contact time) for CSO and obtained a 1.8-3.1 log 10 reduction of E. coli, total coliform bacteria, intestinal enterococci, Aeromonas s, P. aeruginosa, and somatic coliphages, whereas G. lamblia and human viruses (human adenovirus, polyomavirus, norovirus, rotavirus, and enterovirus) were not inactivated.…”

Combined Sewer Overflow pretreatment with chemical coagulation and a particle settler for improved peracetic acid disinfection

“…In parallel after 60 min of contact time residual PAA from sample was quenched by adding 100 mg·L -1 sodium thiosulphate followed by 50 mg·L -1 catalase as described by Chhetri et al, (2014) from sample to enumerate Enterococcus. Our previous study on disinfection of E. coli and Enterococcus from CSO water showed that Enterococcus was more difficult to disinfect from CSO sample with respect to E. coli (Chhetri et al, 2015(Chhetri et al, , 2014. Therefore, disinfection of Enterococcus was only considered in this study.…”

“…Recently we investigated in laboratory scale the possibility to use peracetic acid and performic acids for disinfection of CSO in terms of doses required for disinfection, kinetic of reaction in water and residual disinfectants (Chhetri et al, 2014). The first full scale demonstration of performic acid disinfection of CSO was just described using a sea outfall pipe north of Copenhagen, Denmark as reaction tank (Chhetri et al, 2015). The disinfection efficiency can be influenced by inlet water quality since disinfectant will react with other contaminant in untreated water.…”

Algal toxicity of the alternative disinfectants performic acid (PFA), peracetic acid (PAA), chlorine dioxide (ClO 2 ) and their by-products hydrogen peroxide (H 2 O 2 ) and chlorite (ClO 2 − )

“…Moreover, higher concentration of PAA (~30 mg/L and ~10 mg/L) was not completely degraded after 72 h. PFA and chlorine dioxide are unstable disinfectants. Faster degradation of PFA was observed than PAA when it was used to disinfect combined sewer overflows (Chhetri et al, 2015(Chhetri et al, , 2014 and similarly, faster degradation chlorine dioxide was observed when it was used to remove pharmaceuticals in biologically treated wastewater (Hey et al, 2012). Even though all three alternative disinfectants were almost completely degraded during the first 24 hours of the algal test, clear concentration-response patterns were obtained during the 72 hours incubation (Fig 1).…”

“…In recent years, PFA has been used to disinfect primary and secondary WWTP effluents (Gehr et al, 2009;Ragazzo et al, 2013) and to disinfect combined sewer overflows (Chhetri et al, 2015). PFA is unstable and needs to be generated on-site, when needed, as a quaternary equilibrium mixture of performic acid (PFA), formic acid, hydrogen peroxide and water:…”