The emergence and spread of antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARG) compromise the effectiveness of antibiotic treatments and pose a major public health threat. Here, we investigate the prevalence of ARB, specifically carbapenemase-producing Enterobacteriaceae (CPE) which are resistant to last-resort antibiotics, in hospital wastewater (WW) and WW biofilm, collected from a WW outlet joining the adult intensive care unit (AICU) of the Grenoble University Hospital. The samples were collected monthly over a period of 16 months (January 2023 to April 2024). Samples from January to April 2023 and January to April 2024 were characterized by bacterial cultures. The bacterial flora was rich in human gut and WW bacteria, and CPEs were isolated from all the WW samples. Interestingly, the isolated CPE differed from the 2023 year to 2024: while Citrobacter species carrying mainly the Oxa_48 carbapenemase were isolated from the 2023 time period, only Serratia marcescens strains carrying mainly VIM carbapenemase were isolated in 2024. This indicates that a population switch occurred between April and December 2023, a time period during which the samples were not analyzed by bacterial cultures. To identify whether the various isolates are of the same clonal origin, Enterobacterial Repetitive Intergenic Consensus Polymerase Chain Reaction (ERIC-PCR) on the isolated CPEs is currently performed. Our results have thus shown that the CPE population isolated from hospital WW is dynamic, which might reflect the patient’s carriage of the types of CPEs in the respective ward.