Mechanisms of plastic biodegradation by microorganisms are still poorly understood due to a high variability in environmental conditions. This study aimed to isolate, identify and characterize bacteria with plastic-degrading potential derived from the landfill Getliņi EKO (Riga, Latvia). Among the bacteria selected, Bacillus was the predominant genus identified. Comparative testing revealed the highest non-specific esterase activity in the cultures of B. licheniformis and B. altitudinis. After a six-week batch experiment, a newly developed consortium GPS-2024 biologically reduced the weight of untreated low-density polyethylene (LDPE), polyethylene terephthalate (PET), and high-density polyethylene (HDPE) by 19.44%, 5.99% and 2.99%, respectively. Thermally pre-treated PET and acid pre-treated HDPE resulted in greater weight losses than the respective untreated polymers. Scanning electron microscope showed primarily single cells and microcolonies attached to the surfaces of the granules. Microbial respiration and fluorescein diacetate hydrolysis test suggested that the granules had a stimulating effect on the metabolic activity of planktonic cells. Cultures with untreated LDPE and PET exhibited the highest ecotoxicity for Thamnocephalus platyurus, i.e., by 60.39% and 71.25% of the control, respectively. In conclusion, landfill Getliņi EKO showed to be a promising sampling source for bacteria with ability to biodegrade fossil-based polymers.