Fouling in hollow fiber membrane microfilters used for household water treatment. Journal of Water, Sanitation and Hygiene for Development, In Press, 2014 | doi:10.2166/washdev.2014.206
Authors: Anna Murray, Mario Goeb, Barbara Stewart, Catherine Hopper, Jamin Peck, Carolyn Meub, Ayse Asatekin and Daniele Lantagne
Department of Civil and Environmental Engineering, Tufts University, 200 College Avenue, Medford, MA 02155, USA E-mail: anna.murray@tufts.edu
Pure Water for the World, Trojes, Honduras
Department of Chemistry, University of Maine, Orono, ME, USA
Department of Molecular and Biomedical Sciences, University of Maine, Orono, ME, USA
Pure Water for the World, Rutland, VT, USA
Department of Chemical and Biological Engineering, Tufts University, Medford, MA, USA
The Sawyer PointOne hollow fiber membrane microfilter is promoted for household water treatment in developing countries. Critical limitations of membrane filtration are reversible and irreversible membrane fouling, managed by backwashing and chemical cleaning, respectively. The PointOne advertised lifespan is 10 years; users are instructed to backwash as maintenance. Owing to reduced turbidity and bacterial removal efficiencies, six PointOnes were removed from Honduran homes after 23 months of use. In the laboratory, we tested sterile water filtrate for turbidity and bacterial presence before and after backwashing and chemical cleaning. Sterile water filtrate from uncleaned filters had turbidity of 144–200 NTU and bacteria counts of 13–200 CFU. Cleaned filter effluent was positive for total coliforms.
On one new and one used, cleaned filter, we imaged membranes with scanning electron microscopy and characterized surface elemental compositions with spectroscopy. Images and spectroscopy of the used, cleaned membrane revealed a dense, cake fouling layer consisting of inorganic metal oxides, organic material, and biofouling. Burst fibers were visually observed. This PointOne was thus irreversibly fouled and non-functional after <2 years of use. Further research is recommended to determine: impacts of source water quality on PointOne performance, a cleaning regimen to manage fouling, and an appropriate filter lifespan.
