Wastewater systems are reservoirs of multidrug-resistant (MDR) pathogens, including Pseudomonas aeruginosa, mirroring those found in the hospital effluents. Effective treatment of raw sewage for MDR P. aeruginosa abatement is critical for safe effluent disposal. This study reports the isolation of a novel phage (ɸPRS-1) within the Pbunavirus genus from a pristine stretch of the Ganges River, targeting the MDR strain of P. aeruginosa. Antibacterial and antibiofilm assays of ɸPRS-1 against P. aeruginosa PAO1 demonstrated robust efficacy, achieving log10 reductions of 8.14 in planktonic cells, 9.83 in biofilm inhibition, and 7.01 in biofilm disruption after 24 hours. Additionally, ɸPRS-1 effectively disrupted the preformed biofilm of various other MDR P. aeruginosa strains with >5 log10 reductions. Mechanistically, ɸPRS-1 downregulated quorum-sensing genes and reduced the carbapenemase resistance KPC cluster, validated through qRT-PCR analysis. Evaluation of ɸPRS-1 in raw sewage revealed a 4.2 log10 CFU/mL reduction in the P. aeruginosa counts, highlighting its efficacy in complex environmental matrices. In vitro, cytotoxicity assays confirmed the phage's safety. The use of ɸPRS-1 for tackling MDR P. aeruginosa in the wastewater offers a sustainable alternative, potentially reducing reliance on other treatment methods. The findings have attempted to deliver SDGs 3, 6, 11, 14, and 15.