High-throughput sequencing as a tool for monitoring prokaryote communities in a wastewater treatment plant.

In this study, the DNA metabarcoding technique was used to explore the prokaryote diversity and community structure in wastewater collected in spring and winter 2020-2021 as well as the efficiency of the treatment in a wastewater treatment plant (WWTP) in Ría de Vigo (NW Spain). The samplings included raw wastewater from the inlet stream (M1), the discharge water after the disinfection treatment (M3) and mussels used as bioindicators of possible contamination of the marine environment. Significant differences were discovered in the microbiome of each type of sample (M1, M3 and mussels), with 92 %, 45 % and 44 % of exclusive OTUs found in mussel, M3 and M1 samples respectively. Seasonal differences were also detected in wastewater samples, with which abiotic parameters (temperature, pH) could be strongly involved. Bacteria present in raw wastewater (M1) were associated with the human gut microbiome, and therefore, potential pathogens that could be circulating in the population in specific periods were detected (e.g., Arcobacter sp. and Clostridium sp.). A considerable decrease in putative pathogenic organisms from the M1 to M3 wastewater fractions and the scarce presence in mussels (<0.5 % total reads) confirmed the effectiveness of pathogen removal in the wastewater treatment plant. Our results showed the potential of the DNA metabarcoding technique for monitoring studies and confirmed its application in wastewater-based epidemiology (WBE) and environmental contamination studies. Although this technique cannot determine if the infective pathogens are present, it can characterize the microbial communities and the putative pathogens that are circulating through the population (microbiome of M1) and also confirm the efficacy of depuration treatment, which can directly affect the aquaculture sector and even human and veterinary health.

Wastewater and marine bioindicators surveillance to anticipate COVID-19 prevalence and to explore SARS-CoV-2 diversity by next generation sequencing: One-year study.

This study presents the results of SARS-CoV-2 surveillance in sewage water of 11 municipalities and marine bioindicators in Galicia (NW of Spain) from May 2020 to May 2021. An integrated pipeline was developed including sampling, pre-treatment and biomarker quantification, RNA detection, SARS-CoV-2 sequencing, mechanistic mathematical modeling and forecasting. The viral load in the inlet stream to the wastewater treatment plants (WWTP) was used to detect new outbreaks of COVID-19, and the data of viral load in the wastewater in combination with data provided by the health system was used to predict the evolution of the pandemic in the municipalities under study within a time horizon of 7 days. Moreover, the study shows that the viral load was eliminated from the treated sewage water in the WWTP, mainly in the biological reactors and the disinfection system. As a result, we detected a minor impact of the virus in the marine environment through the analysis of seawater, marine sediments and, wild and aquacultured mussels in the final discharge point of the WWTP.