Alkali-assisted membrane cleaning for fouling control of anaerobic ceramic membrane bioreactor

• Published in: Bioresource technology Vol. 240; pp. 25 - 32
• Main Authors: Mei, Xiaojie, Quek, Pei Jun, Wang, Zhiwei, Ng, How Yong
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2017
• Subjects: Alkalies; Anaerobic membrane bioreactor; Anaerobiosis; Bioreactors; Ceramic membrane; Ceramics; Domestic wastewater; Membrane fouling; Membranes, Artificial; Sodium hydroxide; Waste Disposal, Fluid; Water Purification; Ceramic membrane; Anaerobic membrane bioreactor; Domestic wastewater; Membrane fouling; Sodium hydroxide
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2017.02.052

•An alkali-assisted CEB cleaning method in AnMBR was developed.•0.05–1.30mmol-NaOH/L had positive impacts on anaerobic biomass under short-term exposure.•10–20mmol-NaOH/L backflushing significantly reduced membrane fouling rates and slightly improved methanogenic activities.•12mmol-NaOH/L is cost-efficient and fouling-control dosage. In this study, a chemically enhanced backflush (CEB) cleaning method using NaOH solution was proposed for fouling mitigation in anaerobic membrane bioreactors (AnMBRs). Ex-situ cleaning tests revealed that NaOH dosages ranging from 0.05 to 1.30mmol/L had positive impacts on anaerobic biomass, while higher dosages (>1.30mmol/L) showed inhibition and/or toxic impacts. In-situ cleaning tests showed that anaerobic biomass could tolerate much higher NaOH concentrations due to the alkali consumption by anaerobic process and/or the buffering role of mixed liquor. More importantly, 10–20mmol-NaOH/L could significantly reduce membrane fouling rates (4–5.5 times over the AnMBR with deionized water backflush) and slightly improve methanogenic activities. COD removal efficiencies were over 87% and peaked at 20mmol-NaOH/L. However, extremely high NaOH concentration had adverse effects on filtration and treatment performance. Economic analysis indicated that 12mmol/L of NaOH was the cost-efficient and optimal fouling-control dosage for the CEB cleaning.