Removal of bacteria and viruses from waters using layered double hydroxide nanocomposites

We have identified synthetic layered double hydroxides (LDH) nanocomposites as an effective group of material for removing bacteria and viruses from water. In this study, LDH nanocomposites were synthesized and tested for removing biological contaminants. LDH was used to remove MS2 and φX174 (indicator viruses), and Escherichia coli (an indicator bacterium) from synthetic groundwater and to remove mixed communities of heterotrophic bacteria from raw river water. Our results indicate that LDH composed of magnesium-aluminium or zinc-aluminium has a viral and bacterial adsorption efficiency ⩾99% at viral concentrations between 5.9×106 and 9.1×106 plaque forming units (pfu)/L and bacterial concentrations between 1.6×1010 and 2.6×1010 colony forming units (cfu)/L when exposed to LDH in a slurry suspension system. Adsorption densities of viruses and bacteria to LDH in suspension ranged from 1.4×1010 to 2.1×1010 pfu/kg LDH and 3.2×1013-5.2×1013 cfu/kg LDH, respectively. We also tested the efficiency of LDH in removing heterotrophic bacteria from raw river water. While removal efficiencies were still high (87-99%), the adsorption capacities of the two kinds of LDH were 4-5 orders of magnitude lower than when exposed to synthetic groundwater, depending on if the LDH was in suspension or a packed column, respectively.