Fouling in gravity driven Point-of-Use drinking water treatment systems

This paper describes fouling in simulated Point-of-Use (PoU) systems based on low pressure hollow fiber ultrafiltration membranes. Various operational configurations such as recirculation of feed, discontinuous vs. continuous filtration, and inside/out vs. outside/in were compared to study their effects on fouling and permeate production. Flux values stabilized around 2 L/m2 h for gravity driven (100 mbar) ultrafiltration. Intermittent operation resulted in lower overall hydraulic resistances compared to continuously operated systems. This was due to the low organic loading and relaxation of the fouling layer during periods of standstill. In most experiments the fouling layer mainly consisted of diatoms, inorganic particles and few microbial clusters. The PoU systems investigated can be operated for longer duration without the need for strong chemical cleaning.