Study on the performance of microbial electrolytic cell for the treatment of sulfate wastewater under different microbial source cultivation methods

Microbial electrolysis cell (MEC) offers extensive advantages in treating sulfate-containing wastewater, but problems such as difficulty in microbial attachment and long reactor startup cycle have restricted its development. A systematic investigation of multiple cultivation methods revealed that the use of a bacterial suspension significantly accelerated the startup process of MEC, achieving a sulfate reduction efficiency of 70.2% by cycle 42. The cyclic voltammetric area was on average 1.0-1.2 times higher than that of the other three groups, and a significant increase in the content of extracellular polymers was observed. In addition, the increased bacterial diversity on the biofilms that make up the enriched bacterial solution group promotes the growth of genera such as norank_f_Synergistaceae, Mesotoga, and Thermovirga. Concurrently, high-throughput sequencing was employed to predict the metabolic functional genes of the microbial communities, revealing a higher relative abundance of functional genes associated with biofilm formation and dissimilatory sulfate reduction. These findings reveal the potential of the high-activity inoculum in promoting the construction of cathode biofilms and the efficient operation of sulfate wastewater treatment reactors.