Comparison of MBR and MBBR followed by UV or electrochemical disinfection for decentralized greywater treatment. (15th May 2023)

• Record Type: Journal Article
• Authors: Ongena, Seppe; de Walle, Arjen Van; Mosquera-Romero, Suanny; Driesen, Nele; Gutierrez, Leonardo; Rabaey, Korneel
• Is Part Of: Water research. Volume 235(2023)
• Publication Date: 2023-05-15
• Subjects: Greywater -- Membrane bioreactor -- Moving bed biofilm reactor -- UV -- Electrochemical cell; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2023.119818
• Languages: English
• ISSNs: 0043-1354

Abstract

Highlights: Coupling of electrochemical or UV disinfection with MBR or MBBR greywater treatment. MBR required 10-times lower reactor volume than the MBBR for same greywater feed. Using ceramic membranes in MBR decreased fouling compared to polymeric ones. UV was less sensitive to effluent quality than EC, but provided no residual disinfectant. A fit-for-use approach was proposed, leveraging the respective system advantages. Abstract: Greywater is an attractive source for water reuse at the household or building level, particularly for non-potable applications. Two greywater treatment approaches are membrane bioreactors (MBR) and moving bed biofilm reactors (MBBR), yet, their performance has not been compared so far within their respective treatment flowsheets, including post-disinfection. Two lab-scale treatment trains were operated on synthetic greywater: a) MBR with either polymeric (chlorinated polyethylene, C-PE, 165 days) or ceramic (silicon carbide, SiC, 199 days) membranes coupled with UV disinfection; and b) single-stage (66 days) or two-stage (124 days) MBBR coupled with an electrochemical cell (EC) for in-situ disinfectant generation. Water quality was constantly monitored, and Escherichia coli log removals were assessed through spike tests. Under low-flux operation of the MBR (<8 L· m − 2 · h − 1 ), the SiC membranes delayed the onset of membrane fouling and needed less frequent cleaning compared to C-PE membranes. Both treatment systems met most water quality requirements for unrestricted greywater reuse, at a 10-fold lower reactor volume for the MBR than the MBBR. However, neither the MBR nor the two-staged MBBR allowed adequate nitrogen removal, and the MBBR did not consistently meet effluent chemical oxygen demand and turbidity requirements. Both EC and UV provided non-detectable E. coli concentrations in the effluent. Although the EC provided residual disinfection, scaling and fouling decreased its energetic and disinfection performance over time, making it less efficient than UV disinfection. Several outlines to improve the performance of both treatment trains and disinfection processes are proposed, thus, allowing a fit-for-use approach that leverages the advantages of the respective treatment trains. Results from this investigation will assist in elucidating the most efficient, robust, and low-maintenance technology and configurations for small-scale greywater treatment for reuse. Graphical abstract: Image, graphical abstract