Integrated electro-coagulation and gravity driven ceramic membrane bioreactor for roofing rainwater purification: Flux improvement and extreme operating case

The collected roofing rainwater with high water quality and large water volume, can alleviate the crisis of water resources and fit the Low-Impact Development (LID) concept. In this work, a novel water purification technology, Electro-Coagulation coupled with Gravity-Driven Ceramic Membrane Bio-Reactor (EC-GDCMBR) was developed for the roofing rainwater purification under long-term operation (136 days). EC-GDCMBR system not only exhibited the better effluent quality, but also obtained the greater flux (-32 LMH). The reason contributed to the high perme-ability of ceramic membrane and large porosity of biofilm formed by floc growth (-36 mu m) during the EC process, which was also proved by SEM image. The coagulation, adsorption, biodegradation, and coprecipitation of EC-GDCMBR was able to synergistically remove the particulate matter, ammonia nitrogen (NH3-N), Total Phosphorus (TP), organic substances, and heavy metal (i.e., Cr, Zn, and Cu). In particular, via the analysis of bacterial abundance, Extracellular Polymeric Substances (EPS), Assimilable Organic Carbon (AOC), Adenosine Tri-Phosphate (ATP) and Confocal Laser Scanning Microscopy (CLSM), EC could sweep most free bacteria on the ceramic membrane surface, enhancing the biological purification efficiency. Furthermore, a large amount of Pseudomonas (12.4 %-66.7 %) and Nitrospira (1.46 %-3.16 %) in the aggregates formed the biofilms, improved the NH3-N removal. During the long-

Automated summary

This study developed a novel water purification technology, EC-GDCMBR, for the purification of roofing rainwater. The EC-GDCMBR system showed improved effluent quality and greater flux due to the high permeability of the ceramic membrane and the large porosity of the biofilm formed during the EC process. The technology synergistically removed particulate matter, ammonia nitrogen, total phosphorous, organic substances, and heavy metals through coagulation, adsorption, biodegradation, and coprecipitation. Moreover, EC was found to enhance biological purification efficiency and improve NH3-N removal.