Wastewater contains a wide range of biological and chemical markers related to human activity. The collection and analysis of these markers in the effluents (wastewater and sludge) allow make it possible to qualify the public health of the population and to evaluate the impact of the chemicals used in daily life on the environment. In line with these studies, the Innovation Department of SIAAP and its scientific partners (ISA and LEESU) have created an Observatory of the city with the objectives of: • Monitoring the long-term dynamics of known and/or potential pollutants according to French regulations. • Contributing to studies aimed at a better understanding of anthropogenic activities. • Structuring and centralizing data (wastewater and end-of-treatment sludge), ensuring their storage for 10 years. • Providing technical and scientific knowledge by publishing every two years the data generated by the Observatory of the city via the open platform Zenodo. Regarding the pre-treated wastewater, the Clichy pretreatment plant has been chosen as a strategic location because it collects wastewater from the Paris catchment area (2.7 million inhabitants). Data on the wastewater quality during dry weather and on rain events (biological and physicochemical global quality parameters, metals, polycyclic aromatic hydrocarbons – PAHs and polychlorinated biphenyls – PCBs) is available since 2000 (for dry weather) and from 2005 (for rain events). Dataset description The dataset “Dataset _Clichy-SEC-Inlet.xlsx” includes the monthly analysis of various micro pollutants (trace metals, PAHs and PCBs) and usual physico-chemical parameters. The oldest analyses date back to 2000. The dataset “Dataset _Clichy-CSO.xlsx” includes the monthly quantified analysis of various micro pollutants (trace metals, PAHs and PCBs) and usual physico-chemical parameters for samples collected during 384 rain events. The oldest analyses date back to 2005. Details on each analysis are provided in the “Dataset_analyticalmethods_Clichy.xlsx” The following files are available: Dataset _Clichy-SEC-Inlet.xlsx Dataset _Clichy-CSO.xlsx Dataset_analyticalmethods_Clichy.xlsx