Blog #2 Removing Toxic Substances from Our Drinking Water

Removing Toxic Substances from Our Drinking Water

By Jared Lapierre

The fluoride ion is a potentially toxic substance to humans in certain concentrations so it must be monitored in our drinking water very closely to make sure it does not exceed its tolerance. If fluoride exceeds its tolerance level and is ingested by humans it can cause fluorosis. Fluorosis is the cause of the fluoride ion being extremely attracted to the calcium ion in teeth and bones, causing an unnatural development of tooth enamel and bone structure. This means that fluoride levels in food and water must be closely monitored to ensure that it does not exceed the tolerance levels.

Currently there are three ways in which the quantity or fluoride is being controlled in drinking water. The first process involves using another substance to create a precipitate with the fluoride ion so it can be filtered out easily. A similar process to the first is adsorption in which a salt would be added and it would create a bond with the fluoride on the surface of the water again making filtration an easy process. The last uses a semi permeable membrane in a process called reverse osmosis which isn’t very cost effective or maintainable on a large scale. While all three of these processes are currently used the one that will be concentrated on is adsorption using salts, more specifically salts containing aluminum (Karthikeyan 2009).

Aluminum ions and fluoride ions have a strong attraction for each other which makes aluminum salts the optimal choice in the removal of fluoride ions from drinking water. A recent study was conducted on two types of aluminum salts, that were specifically chosen for their properties such as non toxicity and insoluble in water as these should leave no after effects in the water after the removal of the fluoride. The two aluminum salts that were used in this study are aluminium titanate and bismuth aluminate (Karthikeyan 2009).

This experiment was conducted very thoroughly, they covered all aspect from time, temperature, dose size, effects of different levels of pH, the effects of other ions in the water, diffusion and more. The problem with the finished paper is that it is not very specific on why the variables chosen, were chosen. They give details on what they did and exactly how they did it but do not specify why, or how it applies to treating water systems. This leaves room for the reader to view the results an draw their own conclusions, the standing problem with this is that the reader would need to be an expert on the subject or have a strong background in chemistry and biology to make any sense of the results.

Why conduct this experiment then, it was well conducted but it did not answer a single question, it only tested two new products in a non comparable way to the old ones. The paper did in fact address the comparison of these new aluminum adsorbents to the previously used ones but could not directly compare them due to the different experimental conditions (Karthikeyan 2009). This leaves someone thinking that if they are trying to test that these two new aluminum salts make better adsorbents then why was the experiment not set up to directly compare new to old.

The findings of the study concluded that the two aluminum salts had a strong affinity for removing fluoride ions from water, and other solutions in a large range of pH (Karthikeyan 2009). This could mean a great future for the control of fluoride content in drinking water. However until the new adsorbents are compared to the old adsorbents there can be no conclusive answer on which is more efficient or cost friendly. We cannot even determine whether adsorbents are the best approach until properly compared in a similar experiment conditions to precipitates and membrane approaches.

To make any definite conclusions, this new approach to defluoridation must be field tested in direct comparison to old methods of adsorption. If from those test these two aluminum salts are determined to be better at removing the fluoride ion from food and drinking water, the next step is to compare this method to the other forms of defluoridation in direct comparison.

References

Karthikeyan, M. And Elango, K. P. “Removal of fluoride from water using aluminium containing compounds.” Journal of Environmental Science 21.11 (November 2009): 1513-1518.