Arsenic & Fluoride Removal

Arsenic and fluoride are common natural groundwater contaminants with strict health limits. Arsenic is removed by oxidation then adsorption onto iron-based media or coagulation-filtration; fluoride by activated alumina, bone char or reverse osmosis. Media selection and pH control set capacity and run length.

Arsenic and fluoride removal — adsorptive media, coagulation and membranes that strip these geogenic contaminants to drinking-water limits.

Borehole and groundwater supplies are chemically reducing, often free of oxygen, and characteristically carry dissolved iron and manganese, sometimes arsenic, fluoride, ammonia or hydrogen sulphide. Because the raw water is clear at the wellhead and only discolours after contact with air, treatment is designed around controlled oxidation followed by filtration — converting dissolved metals into a filterable floc before they reach the distribution network.

Iron and manganese removal is governed by oxidation kinetics and pH. Iron oxidises readily by aeration above pH 7; manganese is far slower and usually needs a higher pH, a stronger oxidant, or a catalytic filter media that adsorbs and auto-catalyses the reaction. Where biological iron and manganese removal is used, naturally occurring bacteria perform the oxidation within the filter at lower chemical dose, producing a compact, backwashable bed.

Arsenic and fluoride demand specific chemistry: arsenic is best removed after oxidising As(III) to As(V) followed by adsorption or co-precipitation onto iron oxides, while fluoride responds to activated alumina or bone-char adsorption. Continuous water-quality monitoring at the wellhead and post-filter closes the loop, confirming that breakthrough is detected before it reaches consumers and that backwash is triggered on differential pressure or run-time.