title: Strategies for the reduction of Legionella in biological treatment systems.
abstract: A community-wide outbreak of Legionnaire's disease occurred in Warstein, Germany, in August 2013. The epidemic strain, Legionella pneumophila Serogruppe 1, was isolated from an industrial wastewater stream entering the municipal wastewater treatment plant (WWTP) in Wartein, the WWTP itself, the river Wäster and air/water samples from an industrial cooling system 3 km downstream of the WWTP. The present study investigated the effect of physical-chemical disinfection methods on the reduction of the concentration of Legionella in the biological treatment and in the treated effluent entering the river Wäster. Additionally, to gain insight into the factors that promote the growth of Legionella in biological systems, growth experiments were made with different substrates and temperatures. The dosage rates of silver micro-particles, hydrogen peroxide, chlorine dioxide and ozone and pH stress to the activated sludge were not able to decrease the number of culturable Legionella spp. in the effluent. Nevertheless, the UV treatment of secondary treated effluent reduced Legionella spp. on average by 1.6-3.4 log units. Laboratory-scale experiments and full-scale measurements suggested that the aerobic treatment of warm wastewater (30-35 °C) rich in organic nitrogen (protein) is a possible source of Legionella infection.
authors.affiliation: Leibniz University Hannover, Institute for Sanitary Engineering and Waste Management, Welfengarten 1, Hannover 30167, Germany E-mail: nogueira@isah.uni-hannover.de.
authors.forename: R
authors.initials: R
authors.lastname: Nogueira
authors.affiliation: Ruhrverband, Essen, Germany.
authors.forename: K-U
authors.initials: KU
authors.lastname: Utecht
authors.affiliation: University of Bonn, Institute for Hygiene and Public Health, Bonn, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Exner
authors.affiliation: Ghent University, LabMET, Ghent, Belgium.
authors.forename: W
authors.initials: W
authors.lastname: Verstraete
authors.affiliation: Leibniz University Hannover, Institute for Sanitary Engineering and Waste Management, Welfengarten 1, Hannover 30167, Germany E-mail: nogueira@isah.uni-hannover.de.
authors.forename: K-H
authors.initials: KH
authors.lastname: Rosenwinkel
mesh_terms: D017606:Chlorine Compounds / Q000494:pharmacology*; D004202:Disinfectants / Q000737:chemistry / Q000494:pharmacology*; D004203:Disinfection / Q000379:methods*; D005858:Germany; D007875:Legionella / Q000187:drug effects* / Q000502:physiology; D010087:Oxides / Q000494:pharmacology*; D010126:Ozone / Q000494:pharmacology*; D012722:Sewage / Q000382:microbiology; D062065:Wastewater / Q000382:microbiology*; D014871:Water Microbiology
chemical_list: D017606:Chlorine Compounds; D004202:Disinfectants; D010087:Oxides; D010126:Ozone; D012722:Sewage; D062065:Wastewater; C025109:chlorine dioxide