Abstract ENG | Wastewater treatment plants (WWTPs) constitute an important hotspot for the spread of antibiotic resistant bacteria (ARB), which can directly reach natural fresh- and marine- waters, or could be reused for human activities (e.g. agriculture). In both cases, the treated wastewater with its content of ARB can affect the environmental microbial community and ARB could possibly come back to human (e.g. by food-chain) causing resistant infections. According to the Italian and European legislations the treated wastewaters should meet a number of parameters regarding chemical, physical, and microbiological pollutants. However antibiotic resistance is not considered among the parameters to monitor, and running WWTPs are not designed to actively remove determinants of antibiotic resistance, namely ARB and antibiotic resistance genes (ARGs). ARGs content in the effluents from WWTPs is currently under evaluation for the incoming revision of the European Water Directives for the next decade, thus it is reasonable to forecast that a precise definition and a possible reduction of the antibiotic resistome (the total ARGs content of a water sample) in the treated wastewaters will be required in the next future. In WWTPs, the abatement of bacterial abundance is mainly performed by the final disinfection, a step that has a direct impact on the microbial community of the treated wastewater. As also stated above, disinfections to date employed in WWTPs, either chemical (e.g. by peracetic acid, chlorine) or physical (e.g. UV radiation, sand filtration) are not specific in the removal of ARB and in some cases they could even select for ARGs and for bacterial resistant forms (e.g. aggregates). Thus, an appropriated disinfection process should be designed to address this problem. Furthermore, an improvement in the methodology applied to estimate the overall resistome and its potential influence on the environmental microbial community is needed. In fact, to evaluate the resistome of an environmental microbial community, different molecular methods have been used (e.g. high throughput qPCR, metagenomics), however to realistically test the effectiveness of a disinfection process, these methods should be coupled with a dedicated transcriptomic analysis in order to understand which ARG, mobile elements, and bacterial taxa are expressed and can possibly affect the environmental microbial community. With the DISARM project we aim to design and to test two innovative disinfection processes i.e. (i) ZVI (Zero Valent Iron)-Fenton in presence of H2O2; and (ii) membrane process, performing a selective removal of contaminants by surface exclusion based on size and on charge. These innovative processes will be compared with a classical disinfection based on UV radiation, in use at the selected WWTP, in terms of removal and reduction of the expression of ARGs, mobile elements, metal resistance genes, toxin-antitoxin systems (responsible of the selection of ARGs) and pathogenic bacteria. The best performing disinfection process will be selected with the objective to return to the environment a treated wastewater of high quality, possible reusable for human activities, without affecting the environmental or human microbial community and without promoting the spread of resistances in it. |