###### Abstract  
This study investigates the impact of extreme weather conditions on the performance of a wastewater treatment plant (WWTP) in Como, Italy, in terms of influent (inf) and effluent (eff) quality parameters. During winter (October-December), the average temperature was 8.76 \({}^{\circ}\)C \(\pm\) 11.43 \({}^{\circ}\)C, with 7.01 mm rainfall, while summer (May-September) averaged 23.24 \({}^{\circ}\)C + 6.2 \({}^{\circ}\)C with 5.2 mm rainfall. Despite seasonal variations, the pH levels remained consistent. Phosphorus removal by the WWTP was efficient, with the winter influent averaging 4.16 \(\pm\) 5.53 mg/L, the winter effluent averaging 0.33 \(\pm\) 1.06 mg/L, the summer influent averaging 3.53 \(\pm\) 2.9 mg/L, and the summer effluent averaging 0.31 \(\pm\) 0.75 mg/L. The COD and BOD\({}_{5}\) levels showed seasonal trends, with a higher winter-influent COD (450.43 \(\pm\) 560.56 mg/L) than in summer (410.96 \(\pm\) 302 mg/L). These higher winter values of effluent may be due to lower biological activity at cooler temperatures, affecting the efficiency of organic matter breakdown and treatment. The winter influent BOD averaged 249.57 \(\pm\) 220.42 mg/L, with the winter effluent being 2.95 \(\pm\) 2.04 mg/L, while the summer influent BOD was 214.44 \(\pm\) 345.5 mg/L and the summer effluent was 3.01 \(\pm\) 7.5 mg/L. The TSSs and Total-N showed similar seasonal patterns, with there being slight decreases in the TSSs removal efficiency during warmer months. Although microplastic pollution was not directly analyzed in this study, wastewater treatment plants play a crucial role in mitigating microplastic contamination. Despite rainfall influencing the phosphorus and organic load concentrations, the studied plant maintained over 90% pollutant removal efficiency, demonstrating resilience and compliance with regulatory standards. The WWTP's consistent COD and BOD\({}_{5}\) reductions highlight its robust performance amid climate variations  
wastewater treatment; climate change; environmental protection; tourist region; rainfall; temperature +
Footnote †: journal: Applied sciences
These challenges are compounded by the effects of climate change, which has already begun to alter WWTP operations in two key ways: extreme weather events, such as floods, can overwhelm treatment systems, leading to untreated sewage overflow, while droughs can reduce water usage, diminishing treatment efficiency. Moreover, warmer temperatures have been shown to enhance the efficiency of both natural and non-mechanized treatment processes [8; 9]. Although the primary focus of this study is on the impact of seasonal variations in temperature and precipitation on the performance of a WWTP at Lake Como, it is important to acknowledge the growing concern over microplastic pollution in aquatic environments. Microplastics--durable, lightweight materials such as polyethylene (PE), polyethylene terephthalate (PET), and polypropylene (PP)--are increasingly found in treated wastewater, contributing to ecological degradation. Microplastics persist in aquatic environments despite removal efficiencies of 89-95% in wastewater treatment plants (WWTPs) [10; 11; 12]. These pollutants, alongside drinking water safety concerns in Lake Como [13; 14], highlight the need to understand how climate variability affects WWTP performance. Globally, inadequate plastic waste management, as in Africa, underscores the broader impact of microplastic pollution [15]. This study addresses these issues by examining climate impacts on WWTPs to enhance management practices and protect Lake Como's ecosystem and socio-economic value [16; 17]. While not the central focus of this study, it is crucial to recognize that wastewater treatment systems play a role in mitigating microplastic contamination. The existing research has shown that WWTPs can achieve high removal efficiency for microplastics, ranging from 89% to 95%, underscoring the importance of effective wastewater treatment in protecting water quality and aquatic life [10; 12].