Engineering demonstration of the remediation of urban water using a novel MES enhanced ecological floating bed: From construction to long-term performance

Abstract

An innovative ecological floating bed coupled with sedimental microbial electrochemical system (ECOFB-MES) was designed for urban water remediation. A demonstration-scale ECOFB-MES of approximately 500 m2 was firstly constructed to perform the remediation of 8040 m2 urban water located in Nanning, Guangxi Zhuang Autonomous Region, China. During one-year operation, the COD, NH4+–N, NO3¯–N and TP concentrations stabilized around 10.3 ± 4.0 mg/L, 0.04 ± 0.02 mg/L, 0.61 ± 0.27 mg/L and 0.12 ± 0.05 mg/L from May 2021 to December 2021. The COD, TN and TP removal loads in April when MESs were connected were 72.47 g/d/m2, 4.26 g/d/m2 and 0.39 g/d/m2, which were 3.6, 15.3 and 2.8 times higher than those in January (open circuit). The average TC removal efficiency of sediment near anode was 36.7 %, which was 2.4 times higher than that of sediment far from anode (15.5 %). The average current of the MESs improved from 0.6 ± 0.1 mA to 32.0 ± 2.9 mA with reducing external resistance gradually, which was responsible for higher TC removal efficiency and lower dissolved oxygen (DO) concentration (7.78 ± 1.35 mg/L), which could enhance nitrogen removal. The MES enhanced the total number of species and the bacteria diversity of polyester fibers and roots in the same coupled system. The dominant functional bacteria such as Pseudomonas, Gemmobacter, Aeromonas and Arthrobacter beneficial for oxygen reduction and nitrogen removal were found on biocathode, and this indicated that biocathode of present system could reduce nitrate mainly through heterotrophic nitrification and aerobic denitrification. Results from the president research indicated that the ECOFB-MES provides a rewarding reference for practical application of polluted urban water remediation.