Rural drinking water treatment system combining solar-powered electrocoagulation and a gravity-driven ceramic membrane bioreactor

Abstract

• Natural energy was successfully used to power a water treatment system. • Solar-powered electrocoagulation produced large flocs at a low current density. • The gravity-driven membrane bioreactor achieved a high flux of 25 L/m 2 h. • Large flocs and membrane rejection facilitated the enrichment of useful microbes. • Nitrogen was largely removed by Nitrospira and Diaphorobacter bacteria. Rural water treatment is generally more challenging than urban water treatment. This study proposed a novel rural water treatment system effectively harnessing solar energy and gravitational hydropower. Influent was initially fed to a solar-driven electrocoagulation unit, in which UV 254 level was reduced (by almost 60%) and large flocs (averaging up to 66.2 μm in diameter) were formed. The effluent was then introduced to a gravity-driven ceramic membrane bioreactor (GDCMBR) at different water head differences (ΔH = 0.5 or 1.0 m). Generally, applying the greater water head difference (ΔH = 1.0 m) did not enhance removal of turbidity and organic matter, but it led to a reasonably high flux (25.9 L/m 2 /h). The GDCMBR enriched various useful microorganisms such as nitrifiers ( Nitrospira bacteria), and denitrifiers ( Diaphorobacter bacteria), enabling almost complete elimination of NH 3 -N and NO 2 – -N. Overall, the findings of this study suggest the possibility of sustainable operation during rural water treatment.