# Preliminary Analysis of the Water Quality Status in an Urban Mediterranean River
## 1 Introduction  
Urban rivers are important ecosystems that promote health, prosperity and wellbeing in cities, regarding both public welfare and community livelihood. Rivers offer places to walk next to river banks, boat or paddle, fish, or just sit and relax, refresh, and renew. It is therefore crucial that people are able to safely access and interact with these spaces. Nevertheless, several pollution sources driven by human activity contribute to urban river pollution, including direct discharge from industrial facilities and sewage treatment systems, agricultural runoff, recreational activities themselves and illegal actions [1]. Urban diffuse pollution from cities and transport carries pollutants from roads and urban surfaces into storm drains and out into watercourses at many locations along the river. Moreover, the atmospheric deposition, storm water and urban runoff from urban surfaces may carry various contaminants [2] including toxic metals, organic pollutants, pathogenic organisms and pharmaceuticals such as antibiotics, which create extensive environmental and human health concerns [3]. Additionally, many urban rivers have been channeled, buried or otherwise confined with the impacts of hydro-morphological alterations, enhancing the risk of further degradation in both water quality and quantity [4, 5]. Water quality conditions are commonly assessed by indicators including physicochemical parameters [6], faecal indicator bacteria [7, 8] and polycyclic aromatic hydrocarbons (PAHs) [9]. The latter pose a serious risk to humans, and are linked with infection or illness from waterborne pathogens during contact-recreation [10]. Guideline values for fresh water recreational water were first presented at the World Health Organization (WHO, 2003),based on a tolerable impact of \(<\)1-5% gastrointestinal disease for voluntary recreational activities, and many countries use _Escherichia coli_ (_E. coli_) bacteria as an indicator in fresh water with a 100 cfu/100 mL threshold of risk, based on findings of [11]. The bacterial concentration in rivers is determined by faecal pollution from point and diffuse sources [12]. _E. coli_ bacteria replaced faecal coliforms as a more purposeful index of faecal pollution because _E. coli_ specifically indicate the presence of faeces from warm-blooded animals. It is considered an indicator of recent faecal pollution due to its higher decay rate than intestinal _Enterococci_ in water [12]. In 2012, the Environmental Protection Agency (EPA) updated the water quality criteria recommendations for recreational waters, including both _Escherichia coli_ and _Enterococci_ as indicators for faecal contamination. The new criteria are designed to protect primary contact recreational uses (e.g., swimming, bathing, surfing, water skiing, water play by children etc.) in which a high degree of bodily contact with water, immersion and ingestion are likely. These recommendations depend on the latest research and science that show a link between gastrointestinal and respiratory illnesses and faecal contamination in recreational waters. _E. coli_ guidelines for recreational water quality criteria have been developed by New Zealand (MFE, 2003), EU (Directive 2006/7/EC), the World Health Organization (WHO, 2021), Australia (NHMRC, 2008), the United States Environmental Protection Agency (USEPA, 2012) and Canada (HC, 2012). MFE, 2003 sets the recommended standard of _E. coli_ (maximum concentration) in recreational water at 550 cfu/100 mL based upon a statistical threshold value of the 95 th percentile, while EU sets 900 cfu/100 mL based upon a 90 th percentile evaluation. Additionally, WHO and NHMRC set the standard at 500 cfu/100 mL based upon a statistical threshold value of the 95 th percentile. These are draft recommended concentrations to safeguard people from primary contact during recreational use. The presence of polycyclic aromatic hydrocarbons (PAHs) is also examined within the context of this paper.