Performic Acid Disinfection as tertiary Treatment

Abstract

Currently there are no microbiological requirements for the effluents of a wastewater treatment plant. However, an advanced decrease of the microorganisms can be needed. If the goal for disinfection is required, the EU Bathing Water directive [1] tackles indicator organism for disinfection: the intestinal enterococci and Escherichia coli. However, microorganisms can be ranked with respect to their susceptibility to inactivation by different disinfection processes. In this study, pathogenic bacteria and viruses are investigated in order to determine the inactivation for different disinfection treatment processes. Especially performic acid was investigated in a large demonstration plant for three month. The aim of this study was to evaluate not only the removal efficiency on E.coli, enterococcae, but also coliphage, F+ bacteriophage, humanpathogenic adeno- und norovirus. Chemical disinfection with performic acid was easy to install and could be operated steady state without major problems. For the Indicator organism such as E.coli and intestinale enterococcae the quality achieved meets the guide value for good standard of the EU-Bathing Water Directive [1]. E.coli and enterococcae are removed with 3 log and 2.6 log removal, respectively. Reduction rate for chemical disinfection is lower than for UV-radiation and ozonation. However, the viruses (e. g. reduction rate of 1.9 log for somatic Coliphage) and giardia were not removed effectively by performic acid. If the disinfection process established a filtration, e. g. microsieve/UV, viruses and even parasites are removed with high log-removal of 2 log. In comparison to UV-radiation (retention time < 1–2 s) chemical disinfection requires at least a retention time of more than 4–5 minutes, but not much longer to be still economical. Chemical treatment has low investment but high operational costs. Therefore, to take a decision it is recommended to conduct a specific case study.