Effects of different external voltages on simultaneous heterotrophic removal of sulphate and nitrate in a bioelectrochemical reactor: degradation efficiency, formation of elemental sulphur and bacterial community structure

摘要

A bioelectrochemical reactor (BER) with an anaerobic biocathode was used for simultaneous heterotrophic removal of nitrate and sulphate. Different external voltages in range from 0.1 to 0.5 V were applied to investigate its effects on the degradation efficiencies, the formation of elemental sulphur and bacterial community structure. The results indicated that the effects of external voltage on the removal efficiencies of targeted pollutants were unsimilar. Chemical oxygen demand (COD) was highly affected and nitrate was the lowest affected by the variation in the external voltage. Furthermore, the removal rate of sulphate was attributed to the fact that sulphate was not affected entirely by voltage. Notably, the removal efficiency did not continuously increase with increasing voltage. The dominant genera in the reactors were Pseudomonas, Comamonas, Chryseobacterium, Stenotrophomonas, Desulfococcus and Sphingobacterium, respectively. Despite the similarities between the dominant genera, the application of external voltages resulted in variation of abundance of each microorganism in each BER. The results indicated the possible formation of elemental S during the reduction of sulphate.