Assessment of low-cost cartridge filters for implementation in household drinking water treatment systems

Abstract

In regions where houses are sparsely located, traditional centralized water treatment plants are not economically feasible, with household water treatment (HWT) systems commonly used to provide potable water for a range of household activities. Filtration prior to disinfection is essential, and due to their ease of use and small footprint, cartridge filters are commonly employed. In this work, readily available commercial filter types (spun, wound and pleated) of different micron ratings (10, 5 and 1) were tested for the removal of turbidity either alone or in series via simulated large volume pilot trials. Water with an initial turbidity of 40 ± 10 NTU was prepared using fine test dust (ISO 12103-1, A2) with the turbidity removal efficiency, pressure drop, total capacity and lifespan of the filters evaluated.To increase useable filter lifetime upon reaching the 1 bar pressure limit, a series of washing steps were employed to regenerate the filters. Whilst pleated filters could be efficiently cleaned, spun and wound filters could not, and were discarded after single use. In pilot trials, the volume of turbid water filtered varied from 0.85 m3 with a 1 micron wound filter to 6 m3, with 5 and 1 micron pleated filters in series, which following regeneration could be used for three filtration cycles. For pleated filters, turbidity removal efficiency improved over time as a cake built up resulting in the effluent turbidity reaching acceptable quality (<5 NTU). This criterion continued to be achieved with repeated cycles of washed pleated filters, thereby significantly reducing the cost and improving sustainability of the HWT system. Field trials were carried out with a similar HWT system (5 and 1 micron spun filters) installed in households of rural communities in Curiti, Colombia. Turbidity was effectively removed from natural water (reduction to <1.2 NTU) with improved efficacy in comparison to synthetic water samples due to the large particle size distribution observed in the natural water.