Improving Antibacterial Performance of Household Water Filters with a Silver-Embedded Ceramic Tablet

Abstract

In 2020, one in four people did not have safely managed drinking water in their homes. Household water filters can reduce microbial load but are susceptible to recontamination. This study evaluated the bacterial reduction of several water filters with and without a silver-embedded ceramic tablet (MadiDrop+) in both the laboratory and household settings. In laboratory tests, after 24 h, Kohler Clarity filters with MadiDrop+ halves split between upper and lower reservoirs removed 6.0 log E. coli, whereas filters alone removed 2.7 log E. coli. After 2 h, Rama Water carbon filters with MadiDrop+ halves split between reservoirs removed 3.3 log E. coli, whereas filters alone removed 1.7 log E. coli. After 2 h, ceramic pot filters with a MadiDrop+ in the lower reservoir removed 3.9 log total coliform bacteria (TCB), whereas filters alone removed 2.8 log TCB. In households, effluent TCB [colony-forming units (CFU)/100 mL] was between 0 and 12, 1 and 36, and 509 and 5,916 when the MadiDrop+ was in the lower reservoir, split between reservoirs, and not present in Kohler Clarity filters, respectively. Silver levels were ≤100 μg/L, the drinking water limit set by the USEPA. The addition of silver via a MadiDrop+ either wholly in the lower reservoir or split between upper and lower reservoirs of household water filters improved bacterial reduction in both laboratory and household settings. Drinking untreated water can lead to waterborne disease. Household water filters are a popular option to treat water in-home, but some pathogens still can pass through the filters. Chemical disinfection via silver can kill pathogens but does not remove any particles from water. This study tested water filters with and without a silver-embedded ceramic tablet, the MadiDrop+, in a laboratory setting and in households in rural South Africa. The addition of a MadiDrop+ tablet to three types of household water filters improved bacterial disinfection in most cases. In a laboratory setting, ceramic pot filters, Rama carbon filters, and Kohler Clarity filters removed more bacteria when a MadiDrop+ was added to the lower reservoir of the filter or was split between upper and lower reservoirs. Households in a rural community in Limpopo, South Africa were given Kohler Clarity filters with either a MadiDrop+ in the lower reservoir, a MadiDrop+ split between reservoirs, or no MadiDrop+. Over 4 weeks of use, filters with the MadiDrop+ had 0–36 colonies of total coliform bacteria per 100 mL of treated water, compared with 509–5,916 colonies from filters without MadiDrop+. In both laboratory and household settings, the addition of silver from a MadiDrop+ tablet increased bacterial removal from water filters. It may be beneficial to combine household water filters with a chemical disinfectant to remove more bacteria and decrease instances of waterborne disease.