Operational Efficiency and Fouling Mechanism of a Novel Swinging Ultra-Fine Screen
Municipal wastewater treatment plants in China face excessive influent grit loads and carbon source deficiencies, while conventional pretreatment (screening, grit chambers, primary sedimentation) exhibits low fine grit removal and poor carbon retention. A novel swinging ultra-fine screen with a screening precision of 0.1 mm was developed and tested at a pilot scale of 1000 m³/d. Systematic evaluation of screens with apertures from 0.05 to 0.4 mm was conducted, with mechanisms analyzed via particle size distribution, COD fractionation, and fouling layer characterization. The 0.1 mm screen achieved an SS removal efficiency of 89.3%, significantly higher than 57.4% for conventional processes, while COD removal was only 9.5% versus 28.6%, corresponding to a carbon source retention of 93%. The device nearly completely retained particles >0.1 mm and achieved >98% removal for particles in the 0.075–0.1 mm range. Performance remained stable under fluctuating COD and SS conditions. A three-stage fouling theory for micro-screens was proposed. This work represents the first application of 0.1 mm screening precision in pretreatment, markedly improving fine grit retention and carbon source preservation, with strong resilience to water quality variations.