Enhanced organics removal and partial desalination of high strength industrial wastewater with a multi-stage microbial desalination cell

Abstract

Conventional microbial desalination cells (MDCs) extract organic energy from wastewater for in situ desalination of saline water, but cannot treat industrial wastewater containing high strength organics that may cause blocking in the thin membrane stack. In this study, a multi-stage MDC (M-MDC) was fabricated and operated for simultaneous treatment and desalination of diluted industrial wastewater. With wastewater (COD: 8723±456mg/L, conductivity: 24,612±772μS/cm) flowing serially from anode-1→cathode-1→anode-2→cathode-2, the maximum power density of the M-MDC reached 566.1mW/m2, with removal efficiencies of COD, TN, NH4+-N, and conductivity reaching 97.8%, 90.6%, 98.4%, and 31.6% respectively with addition of 1V external voltage. The high strength organics were significantly removed due to alternative anaerobic/oxic conditions, the nitrogen removal was enhanced by simultaneous electrical migration and biological nitrification/denitrification. Moreover, the addition of external voltage enhanced current generation (67.4±3.9mA), desalination efficiency, coulombic efficiency (14.1%), and organics removal in two anodes (47.3%), producing an effluent (COD <500mg/L, TN<15mg/L) qualified to be discharged into municipal wastewater pipe systems. These results indicated great potential of M-MDC to work as a pretreatment technology for high strength industrial wastewater.