The aim of the study was to establish the relationship between indicators of preliminary treatment, fermentation, and membrane processing of wastewater and the final level of its environmental safety. The study employed gravimetric, spectrophotometric, chromatographic, titrimetric, microbiological, and membrane-filtration methods using accredited laboratory instruments to assess the physico-chemical, gas-related, and environmental parameters of wastewater. Pre-filtration ensured a substantial reduction in pollutants: suspended solids decreased from 320 to 145 mg/L (-54.7%), turbidity from 68 to 24 NTU (-64.7%), biochemical oxygen demand from 185 to 128 mg O₂/L (-30.8%), and chemical oxygen demand from 420 to 295 mg O₂/L (-29.8%). The biogas formation potential increased from 0.21 to 0.24 m³/kg of removed chemical oxygen demand (+14.3%). In bioreactors, the thermophilic regime (+55°C) demonstrated higher values: the methane CH₄ fraction reached 66-71%, biogas yield amounted to 0.31-0.36 m³/kg, and hydrogen sulphide H₂S decreased to 110-150 ppm. Membrane post-treatment reduced total organic carbon from 22-28 to 4-6 mg/L, adsorb-able organic matter from 2.8-3.4 to 0.4-0.6 mg/L, and the silt density index (SDI) from 6.5-7.2 to 1.2-1.6 units. After complete treatment, nitrites decreased to 0.08-0.12 mg/L, microplastics to 110-180 particles/L, and residual toxicity increased to 82-91% survival, which confirms the environmental safety of the obtained permeate. The results obtained are of practical value for engineers of wastewater treatment facilities and environmental services, who may apply them to optimise filtration, biogas fermentation, and membrane post-treatment of wastewater.