The Effect of Calcium Carbonate Bioprecipitation on Escherichia coli Leaching in Sand Column

Prediction of bacteria transport to groundwater is very important to prevent water resources from coliform bacteria pollusion. The objective of this study was to investigate the effectiveness of microbially induced calcium carbonate precipitation (MICCP) in preventing the transport of Escherichia coli as an indicator coliform. For the MICCP process, the sand sample was poured into PVC tubes (with inside diameter of 4.8 and height of 14.92 cm) and incubated for 3 days in the presence of Sporosarcina pasteurii. After the stablishment of steady-state flow, 0.1 pore volume of Escherichia coli suspension (108 CFU/mL) was added to the sand column and the leaching was followed with distilled water. The column effluent was sampled in 0.1 to 5 pore volume. After leaching, the sand column was sliced into five sections (~3 cm), and the number of E. coli trapped in each slice was measured using the plate count method in EMB agar culture medium. Leaching was also carried out in control sand column. The effect of MICCP treatment and its interaction with pore volume was significant (p<0.05) on Escherichia coli count in effluent. The effect of depth and its interaction with MICCP treatment were significant (p<0.05) on E. coli residuals and bioprecipitated calcium carbonate in the column. Overall, the role of biopreciptated calcium carbonate was significant in bacteria filtration, as it decreased the sand column hydraulic conductivity and reduced the number of E. coli in column effluents.