A biofilm model for assessing perchlorate reduction in a methane-based membrane biofilm reactor

- A model describing perchlorate reduction in a methane-based MBfR was developed.
- The model was verified by experimental data under different operational conditions.
- The stratified microbial distribution in the biofilm was reveal by model analysis.
- Over 80% perchlorate removal efficiency can be achieved with proper PCH4 and LClO4.
- The perchlorate reduction could be affect by nitrate and nitrite concentrations.

Perchlorate (ClO4−) is recognized as an important contaminant in surface water and groundwater, which would pose health risks at very low concentrations. A methane-based membrane biofilm reactor (MBfR) has been successfully demonstrated for perchlorate reduction, which provided an alternative solution for perchlorate remediation with low cost. In this work, a multispecies biofilm model was developed to evaluate perchlorate reduction in the methane-based MBfR under different operational conditions. The model was calibrated and validated using the experimental data from the long-term operation of the MBfR at seven distinct stages. The results suggested that the developed model could satisfactorily describe perchlorate reduction and denitrification performances in the MBfR (R2 > 0.9). The modeling results provided insight into the microbial community distribution in the biofilm, with aerobic methanotrophs and perchlorate reduction bacteria being mainly located at the membrane side (∼60%) and heterotrophic bacteria being situated near the liquid side (∼50%). The model simulations indicated that over 80% of perchlorate removal efficiency could be achieved through controlling the optimal combinations of methane pressure (PCH4) and perchlorate loading (LClO4) (e.g., applying a PCH4 of 30 kPa at a LClO4 of 0.08 g Cl/m2/d). In addition, the perchlorate reduction would be inhibited by the presence of nitrate and nitrite in the MBfR, which should be appropriately controlled during the future practical application of the promising process.

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