Second life of water and wastewater in the context of circular economy - Do the membrane bioreactor technology and storage reservoirs make the recycled water safe for further use?

In recent years water demand drastically increased which is particularly evident in tourism-burdened mountain regions. In these areas, climate neutral circular economy strategies to minimize human impact on the environment can be successfully applied. Among these strategies, treated wastewater reuse and retaining water in storage reservoirs deserve particular attention. This study aimed to determine if recycled water produced with two circular economy systems, namely membrane bioreactor treatment plant (MBR) with UV-light effluent disinfection and a storage reservoir, is safe enough for further use in green areas irrigation in summer and artificial snow production in winter. The assessment was based on the presence and concentration of antimicrobial agents, antibiotic resistant bacteria, antibiotic resistance genes, bacterial community composition and diversity. The treated water and wastewater was compared with natural water in their vicinity. Both systems fulfill the criteria set by the European Union in terms of reclaimed water suitable for reuse. Although the MBR/UV light wastewater treatment substantially reduced the numbers of E. coli and E. faecalis (from e.g. 32,000 CFU/100 ml to 20 CFU/100 ml and 15,000 CFU/100 ml to nearly 0 CFU/ml), bacteria resistant to ampicillin, aztreonam, cefepime, ceftazidime, ertapenem and tigecycline, as well as ESBL-positive and multidrug resistant E. coli were highly prevalent in MBR-treated wastewater (88.9 %, 55.6 %, 33.3 %, 22.2 % and 11.1 % and 44.4 and 55.6 %, respectively). Applying additional tertiary treatment technology is recommended. Retaining water in storage reservoirs nearly eliminated bacterial contaminants (e.g. E. coli dropped from 350 CFU/100 ml to 10 CFU/100 ml), antibiotic resistant bacteria, resistance genes (none detected in the storage reservoir) and antibiotics (only enrofloxacin detected once in the concentration of 3.20 ng/l). Findings of this study point to the limitations of solely culture-based assessment of reclaimed water and wastewater while they may prove useful in risk management and prevention in wastewater reuse.

Anthropogenic pollution gradient along a mountain river affects bacterial community composition and genera with potential pathogenic species.

Mountain regions in Poland are among the most frequently visited tourist destinations, causing a significant anthropogenic pressure put on the local rivers. In this study, based on numbers of 9 microorganisms, content of 17 antibiotics and 17 physicochemical parameters, we determined a pollution gradient in six sites along Bialka, a typical mountain river in southern Poland. The E.coli/Staphylococcus ratio varied evidently between polluted and non-polluted sites, indicating that the possible utility of this parameter in assessing the anthropogenic impact on river ecosystems is worth further investigation. Then, using next generation sequencing, we assessed the changes in bacterial community structure and diversity as a response to the pollution gradient. Proteobacteria and Bacteroidetes were the most abundant phyla in the majority of samples. Actinobacteria were the most abundant in the most pristine (groundwater) sample, while Firmicutes and Verrucomicrobia were more prevalent in polluted sites. Bacterial diversity at various levels increased with water pollution. Eleven bacterial genera potentially containing pathogenic species were detected in the examined samples, among which Acinetobacter, Rhodococcus, and Mycobacterium were the most frequent. At the species level, Acinetobacter johnsonii was most prevalent potential pathogen, detected in all surface water samples, including the pristine ones. Two bacterial taxa-genus Flectobacillus and order Clostridiales showed very distinct variation in the relative abundance between the polluted and non-polluted sites, indicating their possible potential as biomarkers of anthropogenic impact on mountain river waters.

COVID-19 lockdown shows how much natural mountain regions are affected by heavy tourism.

Mountain areas in Poland are among the most frequented tourist destinations and such intensive tourism negatively affects the natural environment. The COVID-19 pandemic and the resulting lockdown restricted travel for a few months in 2020, providing a unique opportunity to observe the studied mountain environment without the impact of typical tourist traffic. This study is based on the determination of antibiotic content, hydrochemical parameters, enumeration of culturable bacterial water quality indicators, antimicrobial susceptibility tests together with extended spectrum beta-lactamase (ESBL) gene detection in waterborne E. coli and NGS-based bacterial community composition at six sites along the Bialka river valley (one of the most popular touristic regions in Poland) in three periods: in summer and winter tourist seasons and during the COVID-19 lockdown. The results of individual measurements showed decreased numbers of bacterial indicators of water contamination (e.g. numbers of E. coli dropped from 99 × 104 CFU/100 ml to 12 CFU/100 ml at the most contaminated site) and the share of antimicrobial resistant E. coli (total resistance dropped from 21% in summer to 9% during lockdown, share of multidrug resistant strains from 100 to 44%, and ESBL from 20% in summer to none during lockdown). Antibiotic concentrations were the highest during lockdown. The use of multivariate analysis (principal component analysis - PCA and heatmaps) revealed a clear pattern of tourism-related anthropogenic pressure on the water environment and positive impact of COVID-19 lockdown on water quality. PCA distinguished three major factors determining water quality: F1 shows strong effect of anthropogenic pressure; F2 describes the lockdown-related quality restoration processes; F3 is semi-natural and describes the differences between the most pristine and most anthropogenically-impacted waters.

How much of antibiotics can enter surface water with treated wastewater and how it affects the resistance of waterborne bacteria: A case study of the Bialka river sewage treatment plant.

This study aimed to gain insight into the presence of antibiotics, occurrence of antimicrobial resistance and prevalence of extended-spectrum ß-lactamase (ESBL) genes in Escherichia coli in surface water, based on the example of the Bialka river, located in one of the most attractive tourist destinations in Poland. Water samples were collected in three sites: in the Tatra National Park (TNP), by the sewage discharge from the local treatment plant (STP) and c.a. 3 km downstream (DSTP). The analyses included determination of antibiotic content, enumeration of bacterial indicators of poor water quality, isolation and identification of Escherichia coli, which was subjected to antimicrobial susceptibility tests and assessment of ESBL-determining genes. Fourteen antimicrobials out of 24 tested were detected in river waters in varying concentrations. Trimethoprim and ofloxacin were most frequently detected. Most antibiotics were absent in the TNP, the highest numbers and the highest concentrations of antibiotics were observed by the STP discharge to decrease their content downstream. Culture-based tests of microbiological contamination showed similar results. Resistance to ampicillin was most frequent (64.5% strains), followed by cefazolin (50%). 20.6% of strains were ESBL-positive, while ESBL-determining gene, blaTEM was detected in 23.8% of E. coli strains. The largest percentage of antibiotic resistant and MDR E. coli strains was detected nearby the STP, indicating that malfunctioning STP may contribute largely to river water contamination downstream, also having significant environmental and economic impact.

Survival and Antibiotic Resistance of Bacteria in Artificial Snow Produced from Contaminated Water.

This study shows microbiological contamination of water in two main Podhale rivers, whose resources are used for the production of artificial snow, and the resulting snow contamination. Thirty-one E. coli strains were isolated from snow at two ski stations in the studied region, their antimicrobial resistance was determined, and the presence of extended spectrum ß-lactamase (ESBL) genes was searched for. The results indicate that the waters of both rivers are severely contaminated, resulting in the contamination of artificial snow with, among others, thermotolerant E. coli. E. coli isolated from snow were most frequently resistant to ampicillin (74.19%) and amoxicillin/clavulanate (51.61% isolates). Aminoglycosides and third generation cephalosporins were most efficient among the tested antimicrobials. Some bacterial strains were multidrug resistant and three strains exhibited the ESBL mechanism. Molecular analyses showed the presence of ESBL genes in the same three strains. Genetic variation among E. coli indicates that only some genotypes are able to survive the artificial snow production process.