Arsenic removal to <1 µg/L with advanced oxidation-coagulation-filtration (AOCF)

Technology

Arsenic is present in water in both organic and inorganic forms, but in drinking water the inorganic forms predominate. These have two possible arsenic oxidation states: As(III) and As(V). As(III) is difficult to remove from water compared to As(V) because of its neutral charge. The effectiveness of the removal process can be improved by first oxidizing As(III) to A(V), for example, by adding permanganate to the water (advanced oxidation). The As(V) can then be adsorbed by ferric hydroxide flocks, which form in the water by dosing it with an iron coagulant, like ferric chloride or ferric sulphate. The objective of this project is the application and optimisation of the AOCF technique for arsenic removal for varying qualities of raw water, as a means of determining the key basic principles for a full-scale implementation.

Challenge

(1) Lab-scale experiments to develop mechanical understanding of the AOCF process. (2) Pilot-scale tests at drinking water treatment sites. (3) Development of a prediction model. (4) Assessment of residuals from the AOCF techniques. (5) Dissemination of results.

Solution

(1) Insight into the performance, robustness, limitation(s) and implications of the AOCF technique for arsenic removal. (2) A prediction model to determine the permanganate and iron dosage rates to achieve <1 μg/L of arsenic. (3) A projection of the quantitative and qualitative impact of enhanced arsenic removal on the residuals of the AOCF technique.