A young engineer in India has released the results of a study suggesting that waste iron rust could be a better solution to the serious worldwide problem of arsenic-contaminated drinking water than traditional hydrous ferric oxide gel.
A 2011 study found that more than one in 1,000 people in more than 70 countries are probably affected by arsenic poisoning. Arsenic exposure can result in degenerative, inflammatory and neoplastic changes of skin and bodily functions. There is no particular remedial action for chronic arsenic poisoning, and low socioeconomic status and malnutrition only serve to increase the risk of chronic toxicity.
Arsenic pollution of the groundwater has especially created serious threat to a number of districts in West Bengal and parts of India like Bharatpur City, Aligarh and Darbahnga. Many out of an estimated population of about 30 million people living in these parts of India are affected by the water’s arsenic content, which is much higher than the WHO limit. The Bureau of Indian Standards (BIS) has already revised the limit of arsenic in drinking water from 0.05 to 0.01 mg/L (or from five to one parts per billion).
Many of the technologies that have been developed to remove arsenic also tend to remove iron from the water. However, iron is actually needed in drinking water to improve arsenic removal in the absorption process.
Shailesh Jha, who works for Meinhardt, used a column filtration method, as it requires a minimal financial investment and is the least prone to errors, to compare three kinds of columns for independent comparisons. The first column contained sand, gravels, a sieve, cotton cloth, glass beads and the hydrous ferric oxide gel. The second column contained the same except the gel, which was replaced by iron rust. The third column contained the same as the second column but with an extra layer of charcoal beneath the iron rust. Contaminated water was then passed over the three columns.
The study found that the arsenic removal capacity of the gel was found to be 80 per cent while the arsenic removal capacity of rust was just over 90 per cent.
Through this study, it is clear that rust technology is more effective than the hydrous ferric oxide (FeOOH) gel, and requires lower investment and less effort, as preparing the gel requires the mixing of sodium hydroxide, ferric chloride and sodium silicate, which is stirred for up to two hours.
Charcoal provides the additional benefit of decreasing unwanted colour impurities and some biological impurities from the water.
With countries such as Bangladesh, China, Taiwan, Thailand, Chile, Argentina and Romania also having arsenic levels several times higher than the maximum contamination level (MCL) (10 parts per billion), this cost-effective solution could significantly improve health levels in these areas and beyond.
