First application of enterophages for monitoring faecal pollution in the temperate Baltic region of Northern Poland.

This study investigates the abundance of enterophages, a novel faecal indicator, in raw and treated sewage at two Wastewater Treatment Plants (WWTPs) in Pomerania, Poland, serving a population of 1.2 million inhabitants. Using the ISO-standardized double agar layer (DAL) method, we compared enterophages with other biological indicators, including coliphages, Escherichia coli, and enterococci. We observed that, although enterophages were present, they formed smaller plaques than coliphages, which complicated detection. Despite this, the study identified a strong presence of E. coli in both raw and treated wastewater, with lower concentrations of enterophages, consistent with other global studies. Enterophages were found to be less abundant than bacterial indicators and coliphages, suggesting a potentially more specific human source. The concentration of enterophages in treated sewage decreased significantly, supporting their potential as indicators of untreated sewage contamination in water bodies. Our results also revealed that enterophages counts in raw sewage were higher than those reported in tropical regions, possibly due to differences in methodology and bacterial strains used. Furthermore, correlation analyses indicated that microbial indicators in raw sewage were linked with chemical parameters such as temperature and orthophosphates, which may influence their presence. The study concludes that while enterophages are viable alternative faecal indicators, their low abundance in treated wastewater highlights the need for further research, including survivability studies and the development of molecular detection methods. This research contributes to the understanding of enterophages in temperate climates and underscores the importance of regional collaboration in optimizing faecal contamination monitoring methodologies.