Fouling of Inorganic Membrane and Flux Enhancement in Membrane-Coupled Anaerobic Bioreactor

ABSTRACT

The fouling mechanism of an inorganic membrane was studied during the operation of a membrane-coupled anaerobic bioreactor (MCAB) when alcohol distillery wastewater was used as a digester feed. It was observed that the fouling mechanism of an inorganic membrane was significantly different from that of conventional membrane filtration processes. The main foulant was identified to be an inorganic precipitate, struvite (MgNH₄PO₄·6H₂O), rather than anaerobic microbial floes. Struvite appears to be precipitated not only on the membrane surface but also inside the membrane pores. The amount of struvite generated during the bioreaction was estimated to be about 2g/L alcohol distillery wastewater. The inorganic foulant was not easily removed by general physical cleaning such as depressurization, lumen flushing, and backflushing. Based on these findings, the membrane fouling was alleviated and thus flux was enhanced by adopting a “backfeeding” mode which has dual purpose of feeding and backflushing with particle-free acidic wastewater used as the feed for anaerobic digestion.

Key Words:

• Membrane-coupled anaerobic bioreactor (MCAB)
• Inorganic membrane
• Struvite
• Backflushing
• Backfeeding