Flux Improvement and Biofilm Performance of an Oblique Gravity-Driven Ceramic Membrane Bioreactor Coupled with Electrocoagulation for Roofing Rainwater Purification

In stormwater harvesting, an effective method to avoid flooding risk and pollutant migration, the collected roofing rainwater can meet part of the domestic water demand and alleviate the water resources crisis. In the current work, an innovative oblique membrane tank layout mode was involved in the electrocoagulation coupled with a gravity-driven ceramic membrane bioreactor (EC/GDCMBR), which was suitable for distributed roof rainwater treatment facilities in rural water-scarce areas. The oblique-EC/GDCMBR system could improve the biofilm formation and porosity in the membrane tank to realize rainwater treatment and reuse. Compared with the traditional layout of lateral-EC/GDCMBR during the long-term operation of 82 days, the oblique-EC/GDCMBR system not only presented the improved permeation flux of ∼40 LMH compared to that of lateral-EC/GDCMBR (∼34 LMH), but also exhibited a lower irreversible fouling resistance (oblique: 1.68 × 109 m–1 vs. lateral: 2.02 × 109 m–1). Moreover, the biofilm characteristics were determined to evaluate the improved flux and biofilm in oblique-EC/GDCMBR. Confocal laser scanning microscopy (CLSM) and adenosine triphosphate (ATP) contents also confirmed the higher biological activity in oblique-EC/GDCMBR. The abundance of Denitratisoma (∼15.38%) in the sludge and Nitrospira (∼3.35%) in the biofilm explained the different nitrogen removal approaches in oblique-EC/GDCMBR. Besides, oblique-EC/GDCMBR exhibited excellent water purification performance with the standard effluent water quality. In a word, this work presents the advantage and reliability of oblique-EC/GDCMBR for roofing rainwater sustainable treatment.