ObjectiveTaking a 1.2 million ton per year differentiated polyester project as an example, this paper analyzes the design, installation, commissioning, and operational effectiveness of a 3 000 m³/d wastewater treatment plant (WWTP) at a chemical fiber enterprise in Jinzhou City. Aiming at the characteristics of the wastewater [poor biodegradability (BOD₅/COD<0.3)], high organic matter concentration (average COD mass concentration is 8 000 mg/L), and containing refractory aromatic compounds and trace acetaldehyde (a highly efficient and stable advanced treatment process system is constructed to overcome the limitations of traditional biological method for low BOD₅ to COD ratio wastewater while achieving dual goals of wastewater resource reuse and energy recovery.MethodsThe designed adopts classified pretreatment + dissolved air flotation + homogenization acidification (enhancing biodegradability) + upflow anaerobic sludge blanket reactor [UASB, organic loading is 8 kg COD/(m³·d)] + two-stage anoxic-oxic (AO, strengthening nitrogen and phosphorus removal) + high-efficiency sedimentation (chemically enhanced phosphorus removal) + fiber disk micro-filtration + ozone catalytic oxidation (degrading refractory organics) + ultrafiltration and reverse osmosis (ensuring reuse water quality). Key design parameters of major structures are systematically introduced.ResultsOperational result demonstrates that the effluent COD concentration is consistently below 30 mg/L. All effluent indices (including ammonia nitrogen and total phosphorus) surpass the Grade A standards of the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918—2002). Simultaneously, the effluent meets Class Ⅳ criteria of the Environmental Quality Standards for Surface Water (GB 3838—2002). COD removal efficiency reaches 99%, with over 80% of the effluent reused, at a treatment cost of 2.63 yuan/m³.ConclusionThis wastewater treatment process performs effectively in practical applications, efficiently treating high-concentration, refractory wastewater from chemical fiber enterprises. It exhibits advantages including high treatment efficiency, operational stability, strong resistance to shock loads, and cost-effectiveness, providing valuable guidance for upgrading or expanding similar WWTPs.