AnMBR Treatment of High-Strength Starch-Based Wastewater: Impact of Cleaning Process and CEBs on Membrane Fouling

Abstract

An anaerobic continuously stirred tank reactor (CSTR) integrated with an external tubular nanofiltration membrane module was operated for 466 days. Studies were conducted to compare the efficiencies in flux and operational permeability recovery of two different chemical cleaning processes. Chemically enhanced backwashes (CEBs) were applied for approximately 176 days of the study and their influence on chemical cleaning performance and membrane fouling rate following chemical cleanings were also investigated. The anaerobic nanofiltration membrane bioreactor used in the study was fed a high-strength, potato starch–based synthetic wastewater (average chemical oxygen demand of 83.4 g/L and average total suspended solids of 5.8 g/L). Important findings were that a static, one-phase cleaning process using caustic cleaning chemicals outperformed a dynamic, three-phase cleaning process that also incorporated acidic cleaning chemicals; the acidic phase of the three-phase cleaning had a detrimental effect on the overall cleaning procedure’s performance; CEBs enhanced the performance of cleaning processes; and, finally, caustic cleaning solutions provided benefits to both membrane cleaning effectiveness and rate of fouling in the short term but may lead to an increased rate of membrane fouling in the long term.