Eaux usées

Wastewater treatment plants (WWTPs) are implicated as hotspots for the dissemination of antibacterial resistance into the environment. However, the in situ processes governing removal, persistence, and evolution of resistance genes during wastewater treatment remain poorly understood. Here, we used quantitative metagenomic and metatranscriptomic approaches to achieve a broad-spectrum view of the flow and expression of genes related to antibacterial resistance to over 20 classes of antibiotics, 65 biocides, and 22 metals. All compartments of 12 WWTPs share persistent resistance genes with detectable transcriptional activities that were comparatively higher in the secondary effluent, where mobility genes also show higher relative abundance and expression ratios. The richness and abundance of resistance genes vary greatly across metagenomes from different treatment compartments, and their relative and absolute abundances correlate with bacterial community composition and biomass concentration. No strong drivers of resistome composition could be identified among the chemical stressors analyzed, although the sub-inhibitory concentration (hundreds of ng/L) of macrolide antibiotics in wastewater correlates with macrolide and vancomycin resistance genes. Contig-based analysis shows considerable co-localization between resistance and mobility genes and implies a history of substantial horizontal resistance transfer involving human bacterial pathogens. Based on these findings, we propose future inclusion of mobility incidence (M%) and host pathogenicity of antibiotic resistance genes in their quantitative health risk ranking models with an ultimate goal to assess the biological significance of wastewater resistomes with regard to disease control in humans or domestic livestock.

Combustion of sewage sludge has become a viable route for sewage sludge management especially as the agricultural use of sewage sludge has become increasingly difficult due to more stringent requirements regarding the quality of sewage sludge. Combustion of digested sewage sludge in dedicated monocombustion facilities is advantageous, as it substantially reduces the volume of the sludge and still allows for a recovery of phosphorus from the sewage sludge ash at a later stage. Despite increasing amounts of sewage sludge being combusted, knowledge on the respective combustion kinetics is still fragmentary. The goal of this study was, therefore, to identify the major combustion reactions of sewage sludge, assess their Arrhenius parameters (activation energy and pre-exponential factor), and assign suitable reference compounds to the individual reactions. For that purpose, experiments were conducted using a thermogravimetric analyzer (TGA). With matrix inversion, we identified 10 individual reactions. Despite the apparent kinetic compensation most likely caused by insufficient precision of the TGA temperature setting, we were able to relate the major reactions of sewage sludge combustion to the combustion of individual reference compounds. In addition to cellulose and lignin, which dominated the weight loss with 35% and 20%, respectively, hemicellulose, xylan, alginate, and calcite were identified. The dominant fraction of cellulose is consistent with recent studies identifying cellulose mainly originating from toilet paper as a major organic constituent in wastewater. As the identified model compounds explain more than 80% of the total weight loss observed, our approach allows a rough speciation of the combustibles of sewage sludge based on TGA experiments.

Noch liegen in der Schweiz erst wenige grosstechnische Erfahrungen mit den Technologien zur Elimination organischer Spurenstoffe auf Abwasserreinigungsanlagen vor. Deswegen wurde 2012 die Plattform «Verfahrenstechnik Mikroverunreinigungen» gegründet und innerhalb des Verbands der Schweizer Abwasser- und Gewässerschutzfachleute (VSA) angesiedelt. Sie soll helfen, Wissen aufzubauen, den Austausch unter den Akteuren zu fördern sowie offene Fragen zu bearbeiten.

Auf einer durchschnittlichen Kläranlage werden Tausende Signale aufgezeichnet. Ihr Potenzial für einen besseren Anlagebetrieb ist beachtlich. Dennoch werden sie selten systematisch genutzt und ausgewertet. Dank einer spezialisierten Software ist es jetzt möglich, eine Anlage und ihre Prozesse schneller und besser zu verstehen, zu überwachen und zu optimieren.

Ist eine ressourcenschonende Abwasserreinigung durch Abwassertrennung und Dezentralisierung realistisch? Rund 40 international bekannte Wissenschafter und Wissenschafterinnen behandeln auf 520 Seiten in einem 2013 erschienenen Buch nuanciert diese Fragestellung. Die Editoren der Eawag diskutieren das Thema des Buches im Schweizer Kontext.

Anaerobic digestion (AD) reduces the amount of waste and generates products of value, such as biogas and nutrient-rich digestate. Contrary to the wide dissemination of digesters in rural areas where animal manure is used as feedstock and despite its apparent potential, AD still plays a negligible role as a treatment option for organic kitchen and market waste in cities of low-and middle-income countries.
This book compiles existing and recently generated knowledge on AD of urban biowaste at small and medium scale with special consideration given to the conditions prevailing in developing countries. Written for actors working in the waste and renewable energy sector, the book is divided into two parts: Part 1 focuses on practical information related to the AD supply chain (substrate-, process-, and product chain), and Part 2 presents selected case studies from around the world.