Development of a continuous flow solar oxidation process for the removal of arsenic for sustainable rural water supply

The aim of this research was to develop a semi-centralised continuous flow solar oxidation system to remove arsenic from contaminated groundwater supplies. Arsenic removal efficiency was evaluated using a full-scale continuous flow reactor under natural sunlight. Initial concentrations of 1000, 500 and 100 μg/L were reduced to below the arsenic drinking water level of 10 μg/L with optimum iron concentrations of 10, 8 and 5 mg/L respectively, requiring a cumulative UV radiation dose of at least 7.5 kJ_UV/L. This demonstrates a more efficient process than found in previous batch studies or small-scale continuous flow studies under artificial light. Experiments were then carried out using Escherichia coli as an indicator of enteric pathogenic bacteria contamination to assess the performance of the process as a combined arsenic removal and disinfection system. All experiments resulted in a marked deterioration in As removal but enhanced disinfection kinetics when initial Fe concentrations were ≥ 10 mg/L. Finally, the settlement of the co-precipitated arsenic (V) and iron (III) was assessed by different combinations of coagulants (aluminum sulphate or Moringa oleifera) and flocculant aids (LT22S or potato starch).