Arsenic and iron removal from water using constructed soil filter—a novel approach

Abstract

Arsenic poisoning is a global problem. It is known that groundwater in Bangladesh and West Bengal predominantly contains As(III) and concentrations of Fe(II) which are often too low for removal of arsenic in optimum quantities. To eliminate arsenic from drinking water, several basic methods such as coagulation, adsorption, ion exchange, filtration, membrane processes, are reported. To deal with this issue on a small to large scale, we present a novel approach to remove arsenic and iron from water by constructed soil filter (CSF).In CSF, As (III) is oxidized to As(V) by media via natural oxidation and subsequently, arsenic is co-precipitated with iron. Here water containing arsenic, iron, and phosphate is passed through the CSF media at the rate of 100 ml/min. Results show a mean residence time of 8.6 min and a holdup of 1.85 l. Results of six runs show that with initial As(III) of 300 µg/l and iron concentration of 5-10 mg/l, residual arsenic levels below 10 ppb and residual iron <0.30 mg/l in water can be achieved.In CSF, no chemicals are needed for the oxidation of As(III) to As(V). The oxidation takes place due to the presence of various oxides such as iron, manganese, aluminum, and the microbial diversity in the media of soil bioreactor. Such a novel technology is also applied for purification of water and wastewater. 

Residence time distribution and oxygen transfer in a novel constructed soil filter

“…Also CSF oxidizes As (III) present in groundwater to As(V) and subsequent removal of As(V) by iron complex gives residual arsenic concentration less than 10 µg L −1 , which conforms with WHO standard for drinking water 4, 5. Similarly, iron and manganese are removed from water by CSF.…”

Deferrisation Physocochimique des eaux Souterraines: Revue

“…Cependant, le taux de déferrisation n'a pas dépassé 50%. Nemade et al (2008) ont traité 40 à 60 l d'eau synthétique riche en fer, en arsenic et en bactéries coliformes par adsorption dans un filtre à sable (CSF : constructed soil filter). Ils ont obtenu qu'une élimination totale de fer est obtenue après 10 h de filtration, un temps de contact de 9,92 min, un pH égal à 7 et une concentration en oxygène dissous de l'ordre de 5 mg/l.…”

Wastewater renovation using constructed soil filter (CSF): A novel approach

“…In view of high oxygen levels, the CSF system finds promise in variety of application viz. water purification and sanitation also CSF shows oxidation of As(III) to As(V) and co-precipitation by iron salt removes arsenic below 10 g/l WHO standard [18].…”