Effect of horizontal-flow velocity on permeate flux and nutrient removal of the novel inclined-tube/oxidation-ditch membrane bioreactor for building wastewater recycling

A hybrid system of the inclined-tube/oxidation ditch-membrane bioreactor or IT/OD-MBR system was developed. While keeping hydraulic retention time (HRT) of 24 h, the system was operated with different horizontal flow velocities of 0.2,0.3 and 0.4 m/s. The perfor-mance and stability of the IT/OD-MBR system for biological nutrient removal and permeate flux was investigated. The results indicated that IT/OD-MBR system could achieve high performances for COD, ammonia and phosphorus removal efficiencies over 90%, 90% and 80%, respectively with the horizontal flow velocity at least 0.2 m/s. Moreover, the predominant foulant of microbial EPS was found to be lipid. For long-term system operation, the optimal horizontal flow velocity at least 0.3 m/s is recommended for the stable permeate flux and nutrient removal performance. High quality of treated ef-fluent from the proposed hybrid IT/OD-MBR system could comply with the water reuse guideline for landscape and gardening purposes.(c) 2022 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

Automated summary

A hybrid system of the inclined-tube/oxidation ditch-membrane bioreactor (IT/OD-MBR) was developed and its performance and stability for biological nutrient removal and permeate flux were investigated. The results showed that the system achieved high removal efficiencies of COD, ammonia, and phosphorus over 90%, 90%, and 80%, respectively, with a minimum horizontal flow velocity of 0.2 m/s. It was also found that lipid was the predominant foulant of microbial EPS. For long-term operation, a minimum horizontal flow velocity of 0.3 m/s was recommended for stable permeate flux and nutrient removal performance. The treated effluent from the proposed hybrid IT/OD-MBR system met the water reuse guideline for landscape and gardening purposes.