A hydraulically optimized fluidized bed UF membrane reactor (FB-UF-MR) for direct treatment of raw municipal wastewater to enable water reclamation with integrated energy recovery

摘要

A hydraulically optimized pilot-scale fluidized bed ultrafiltration membrane reactor (FB-UF-MR) for water reclamation with integrated energy recovery was designed and operated for 576 days with raw municipal wastewater from a local wastewater treatment plant (WWTP). The design of the reactor and the fluidized bed flow regime were optimized by a computational fluid dynamic (CFD) model. By adopting a customized impact plate in the design, the recirculation flow rate could be reduced by approximately 38% lowering the energy demand significantly. Granular activated carbon (GAC) was used as fluidized medium and proved as successful fouling mitigation strategy, even at low concentrations of 1.7-3.3 g/L (based on total reactor volume) or 21-41 g/L (based on fluidized bed volume) as compared to previous studies. The optimal operational conditions of the FBUF-MR were identified at (i) a sustainable flux of 8-10 LMH, (ii) an optimal backwash flux of 1.2 times of the permeate flux, (iii) an operational cycle of 10 min consisting of 9 min filtration and 30-60 sec backwashing and optional 30 sec relaxation. Chemical cleaning was applied every 4-6 weeks during long-term operation. Main foulants of the wastewater matrix were identified by 3D-fluorescence excitation-emission matrix (3D-EEM) measurements coupled with parallel factor (PARAFAC) analysis suggesting that protein-like organic matter were the main constituent of the cake layer. The results of this study indicate that direct treatment of raw municipal wastewater with UF is a promising option. Thus, it is possible to concentrate C and N (in a subsequent treatment step) for improved energy recovery while facilitating water reclamation.