PhD Spotlight: Bio-based arsenic pre-treatment

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Bio-based Arseic Pre-Treatment, PhD, Annaduzzaman Kajol

In Bangladesh over 50 million people are exposed to dangerous levels of arsenic concentrations in their drinking water that greatly exceeds the World Health Organisation guideline. Chronic exposure to arsenic causes a wide range of illnesses, including cancer and skin lesions.

Growing up, Kajol witnessed people suffering from drinking arsenic-contaminated water. He has since dedicated over 10 years of my career working on arsenic mitigation. During his four-year PhD journey at the TU Delft, he developed a novel bio-based arsenic removal technology by relying on groundwater native-iron instead of chemicals.

 Problem Definition:

Conventional filtration of anaerobic groundwater treatment systems uses a combination of aeration and sand filtration. This is effective for iron and manganese removal, but not for arsenic.


Therefore, the novelty for his PhD research was to enhance arsenic removal, by namely anoxic pre-treatment. Anoxic means without oxygen,so without air. The idea is that in the absence of oxygen the groundwater native-iron oxidation is delayed. This is favourable for arsenic removal.


Let me explain. The naturally present iron in anaerobic groundwaters, will form rusty flocs during exposure to oxygen. These flocs have a high dissolved arsenic uptake capacity. However, under fully oxic conditions this uptake is very limited. Kajol tested this concept in a pilot study in Bangladesh with an ananoxic storage tank added prior to water treatment. It was found that by delaying the iron oxidation, indeed arsenic removal was promoted.


This bio-based arsenic pre-treatment has advantages over existing treatments, which are energy intensive, consume chemicals and require expert knowledge. Thus this method is more sustainable for vulnerable communities.

 Do you want to learn more?

Well, for more details I invite you to have a look at my open-access publications, but for now remember that the simple combination of anoxic storage, aeration and sand filtration can improve arsenic removal – depending on locally available materials and crafts.


Annaduzzaman Kajol.

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