Disinfection and removal performance for Escherichia coli and heavy metals by silver-modified zeolite in a fixed bed column

•Silver-modified zeolite column simultaneously removed Escherichia coli and metals.•Complete removal of E. coli achieved after 570 min followed by Cd and Zn (1080 min).•No Pb breakthrough observed during the service life of the column (7920 min).•SEM revealed damaged and lysed cells and E. coli-synthesised Ag particles.•97–98% Ag recovery achieved in the non-modified natural zeolite column.

This study investigates the simultaneous removal of Escherichia coli and metals (Pb, Cd and Zn) in a continuous flow system and provides an insight into the mechanisms involved during bacterial cells kill when in contact with silver-modified zeolite. Results showed complete disinfection and metal removal at 570 min contact time, thereafter E. coli breakthrough followed by Cd and Zn at 1080 min. Due to the zeolite’s high selectivity for Pb removal, no breakthrough was observed up to 7920 min run time. Column performance was influenced by changes in flow rate and bed height, as breakthrough occurred at 240 min when the flow rate was increased from 2 to 5 mL/min and the bed height decreased from 1 to 0.5 cm. Morphological characterisation of treated cells revealed extensive damage and synthesis of nano- and micro-sized silver particles as a part of their defence mechanism. The treated effluent was passed through a non-modified zeolite column with 98% silver recovery achieved. This study showed the capability of this system to simultaneously handle bacterial and heavy metals contamination while providing an insight into the mechanism of disinfection via complex E. coli–silver ion interactions that occur during treatment and demonstrating the potential of silver recovery for reuse.

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