A groundwater containing an unusually high concentration (~4000μg/L) of perchlorate (ClO4-) and significant (~60mg/L) sulfate (SO42-) was treated with hydrogen (H2)-fed biofilms. The objective was to manage the interactions between sulfate-reducing bacteria (SRB) and perchlorate-reducing bacteria (PRB) by controlling the H2-delivery capacity to achieve ClO4- reduction to below the detection limit (4μg/L). Complete ClO4- reduction with minimized SO42- reduction was achieved by using two membrane biofilm reactors (MBfRs) in series. The lead MBfR removed >96% ClO4-, and the lag MBfR further reduced ClO4- to below the detection limit. SO42- reduction ranged from 10 to 60%, and lower SO42- reduction corresponded to lower H2 availability (i.e., lower H2 pressure or membranes with lower H2-delivery capacity). Minimizing SO42- reduction improved ClO4- removal by increasing the fraction of PRB in the biofilm. High SO42- flux correlated with enrichment of Desulfovibrionales, autotrophic SRB that can compete strongly with denitrifying bacteria (DB) and PRB. Increased SO42- reduction also led to enrichment of: 1) Ignavibacteriales and Thiobacteriales, sulfide-oxidizing bacteria that allow sulfur cycling in the biofilm; 2) Bacteroidales, heterotrophic microorganisms likely using organic sources of carbon (e.g., acetate); and 3) Spirochaetales, which potentially utilize soluble microbial products (SMPs) from autotrophic SRB to produce acetate.
- Perchlorate-reducing bacteria
- Sulfate-reducing bacteria
ASJC Scopus subject areas
- Ecological Modeling
- Water Science and Technology
- Waste Management and Disposal