Occurrence and seasonality of pharmaceutical compounds in urban wastewaters in two Portuguese regions

The occurrence of a representative range of pharmaceutical compounds (PhCs) in urban wastewaters was studied in two Portuguese water-scarce regions (Lisbon great area, and Faro - Algarve), involving 55 sampling campaigns during 2.5 years. The results show 16 PhCs (out of the 24 analysed) were quantified in all samples, with similar concentrations in both wastewaters. To understand to what extent seasonality affects PhC occurrence, a statistical analysis was conducted, and daily maximum air temperature was identified as a key factor, with a turning point of 20 degrees C in Lisbon and 22 degrees C in Faro. Some PhCs showed lower concentrations in colder (wet) months due to rainwater dilution (combined sewer systems), whereas others showed higher concentrations, reflecting an increased seasonal consumption and/or slower transformation under lower temperatures and/or shorter hydraulic retention times. Seasonal studies should therefore focus on temperature rather than on calendar seasons, increasingly uncertain due to climate change.

Automated summary

The study found a range of pharmaceutical compounds in urban wastewaters in two water-scarce regions in Portugal, with seasonal temperature variations identified as a key factor affecting the occurrence of these compounds. Research should focus on temperature rather than calendar seasons to account for climate change uncertainties.