Updated project metadata. Wastewater has been extensively studied along the years. However, these studies have been focused on the analysis of small molecules. There are no studies about the proteins present in wastewater and let alone an established method to study them. We propose a method for the study of the proteins in wastewater overcoming their low concentration and the interference of other molecules. Moreover, we differentiate between the proteins that are soluble and the ones in the particulate. This method is based on concentration, lysis and clean-up steps. The samples were analyzed afterward using liquid chromatography coupled to high-resolution mass spectrometry (HR-LC/MS) and the data searched with Proteome Discoverer. Thus, this complete method has allowed us to characterize the proteomic composition of different wastewater samples with a low volume.