Seven-layer and Two-layer Domestic Filters for the Removal of Nephrotoxic Constituents in CKDu prevalent Areas, Sri Lanka: Are these Viable Options?

Consumption of water with nephrotoxic constituents is said to have caused the chronic kidney disease of unknown etiology (CKDu) in Sri Lanka; hence removal of such constituents from potable water has received profound attention. Although seven-layer and two-layer filters have been introduced to the communities in the CKDu prevalent areas, the efficacy of such filters for removal of nephrotoxic constituents has not been adequately evaluated. This study investigates the efficacy of these two filters for improving drinking water quality in the presence of hardness, fluoride, aluminum, and cadmium. Feed water was synthesized with 353, 143 mgL^-1 hardness, 1.7, 0.9 mgL^-1 fluoride, 1.2, 1.3 mgL^-1 aluminum and 1.1, 1.0 mgL^-1 cadmium for seven-layer filter and 342, 149 mgL^-1 hardness, 1.7, 0.8 mgL^-1 fluoride, 1.5, 1 mgL^-1 aluminum and 1.1, 1.2 mgL^-1 cadmium for two-layer filter simulating wet (October, November) and extremely wet (December) seasons, respectively. Filtered water with the seven-layer filter contained 336, 146 mgL^-1 hardness, 1.8, 1.0 mgL^-1 fluoride, 0.7, 0.9 mgL^-1 aluminum, and 0.9, 0.99 mgL^-1 cadmium after 60- and 30-days of operation under wet and extreme wet seasons, respectively. Filtered water with the two-layer filter showed 332, 149 mgL^-1 hardness, 0.6, 1.4 mgL^-1 fluoride, 0.7, 0.3 mgL^-1 aluminum, and 0.5, 0.2 mgL^-1 cadmium after 60- and 30- day operation under wet and extreme wet seasons, respectively. The quality of the filtered water from both filters did not comply with the Sri Lanka Standards (SLS) drinking water quality guidelines. The XRD, FT-IR, ESEM-EDX analyses revealed the presence of calcium, magnesium, fluoride, and aluminum in various layers of filter media of both filters. Such constituents retained in the filter media leached out during filtration resulting in higher levels in the permeate. Hence, the use of seven-layer and two-layer filters does not seem to be a promising solution to remove nephrotoxic constituents present in water in CKDu prevalent areas.