Abstract
Gravity-driven membrane (GDM) systems are promising for decentralized drinking water treatment at the point of use due to their treatment efficiency and low maintenance requirements. To further improve permeate quality in terms of dissolved organic carbon (DOC), adsorption onto activated carbon has been proposed as a pretreatment. In the present study, a novel GDM system with integrated granular activated carbon (GAC) was tested. The performances of polyvinylidene fluoride (PVDF) ultrafiltration membranes (0.45 m²) in combination with two different GAC were compared. The PVDF modules achieved a mean flux between 4.3 and 5.1 L/m²*h at 32.5 mbar. Flux stabilization in GAC/GDM systems was observed during long-term experiments over 272 days. pH increase caused by one GAC after start-up had a severe adverse effect on the flux due to CaCO3 precipitation resulting in a 34 % lower stable flux compared to the other GAC/GDM system. Permeate quality was substantially improved in terms of DOC and UVA254. The organic micropollutants carbamazepine and formylaminoantipyrine were effectively removed in both GAC/GDM systems by at least 88 % and 92 %, respectively. The GDM systems effectively retained Enterococcus faecalis and particles (1–200 μm) by 5.1 and 1.6 log units, respectively. Overall, a GDM system combined with GAC revealed the best performance producing approx. 50 L/d purified water. The GAC/GDM systems were operated without any maintenance measures and improved the permeate quality substantially. Thus, application of the studied GAC/GDM systems is a suitable option for decentralized drinking-water treatment.
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