The recent problem that the townspeople have brought to my attention is the declining quality of the tap water. Many were unpleased with their water, so I decided to conduct my own test instead of using an outside company. Based on the complaints that the residents brought to recent town meetings, I discovered what ions could be causing the problem and began to test them. I used a Hach spectrophotometer and its instructional manual to determine the ions concentrations in the town’s water supply. The ions tested for were total chlorine, copper, fluoride, total iron, manganese, nitrogen (nitrate), phosphate, sulfate, sulfide, and zinc. Following the manual each ion’s concentration was tested for, each ion required a different powder pillow to be mixed with the water sample. Every ion that was tested also needs a blank, a separate test tube that’s concentration would be considered 0.00 mg/L. If the meter went off scale or read over range during any of the test then it would be diluted down and retested until it was in range. Next we tested the pH of the water sample by using pH paper. The pH record value of the water sample was 5. Then we tested the hardness of the water sample. I accurately measured 50-mL of the water sample with a graduated cylinder and poured it into a 125-mL flask. I then added 1-mL of pH 10 buffer and a few drops of the Eriochrome Black T indication solution. At this point the solution was a medium purple color. Then I cleaned a buret and rinsed the inside with a small quantity of 0.010 M EDTA solution. Next, I filled the buret with EDTA solution up to the 0.00 mL mark. Immediately after I warmed a flask to 60°C and then titrated the solution with the EDTA until a permanent blue color was seen. The final buret reading of the EDTA was 42.02 ml. The hardness of the water sample came out to be 827.9 mg/L. The ions that seemed to be causing most of the towns problems were iron and manganese were causing the water to be discolored. Sulfides in the water caused the rotten egg odor. And Zinc was causing the bitter taste. The ions that were all found in high concentration are iron, manganese, nitrates, sulfides and zinc. Nitrates were found very high in concentration, 40.0 mg/L, in the water sample. When nitrates are high in concentration there is no smell or color to indicate it but they are very harmful to infants and pregnant women. Iron and Manganese were also found significantly higher in concentration than recommended. Manganese tested to be 0.3 mg/L and Iron tested to be 5.10 mg/L. These ions are the main cause of the discolored water in the town’s water supply. Sulfides were found to be 42 mg/L in concentration, which is extremely high. Sulfide ions in tap water cause the unpleasant rotten egg odor. Zinc was also found high in concentration. It was 9.95 mg/L in concentration. Zinc adds the undesirable astringent taste to water. These ions are causing major problems with our resident’s water supplies. And some could be harmful to their health if they ingest too much.
One method that could be used to remove the iron and manganese from the water supply is the In-situ method. This method is a process for treating the flow of groundwater through an aquifer with a primary treatment material, such as iron, and then the treated groundwater through a second treatment in which an oxygenated gas is passed in order to oxygenate the dissolved primary treatment material and convert it into an insoluble material. Therefore removing the dissolved primary treatment material from the groundwater. (Removing dissolved metal: Topics by Science.gov)
A method that could be used for removing nitrates from the water supply is Ion exchange. This method removes nitrate ions from the liquid phase by replacing them with another substance, such as chloride, and switches places with nitrate. Special resin beads that are charged with chloride are placed into an ion exchange unit. When the water pass over the beads, the resin then takes up the nitrate in exchange for chloride. While the water continues to pass over the resin, all of the chloride is exchanged for nitrate. Sodium chloride solution is the backwashed in to the resin to recharge it. The backwash solution, very high in nitrates, must be properly disposed of. (cite this)
Both methods of removing the unwanted ions are highly effective and I think both would improve our town water greatly. Nitrate concentration in the town’s water is dangerously high, and is extremely harmful to infants. Eliminating the nitrate ions from the town water should be the top priority. And Ion exchange is a great way to solve the nitrate problem. The ion exchange process for the removal of nitrates is both simple and effective. It can easily remove well over 90 percent of the nitrates and operates in the same manner as a common water softener. ("Removing nitrates with ion exchange”) In situ iron removal has proven to be a viable technique for diminishing the iron concentration in tap water. This method consists of the elimination of dissolved iron and manganese in groundwater before pumping, it is found to be very useful. And I would highly recommend using this technique to contain the iron and manganese problem in our community.
Given that the nitrate level is so incredibly high I believe that it is best to make sure and we find a process that will bring it down considerably. Ion exchange is a great way to solve the nitrate problem. The ion exchange process for the removal of nitrates is simple and highly effective. There are many differing processes that would solve our problem; we should find the best cost-efficient method to remove the nitrate ions from our water supply. Ion exchange is gives you the best quality of removing the harmful ions but it becomes complicated when using mass quantities. The in-situ method is known to be highly effective also, but it targets iron and manganese ions that cause the unwanted discolor of our water. It filters out the rust within the water through oxidation and therefore removes the ions from the water and clearing the water. I think it would be in our town’s best interest to consider using both of the methods to clear our water of the unwanted ions. These methods would eliminate three of the ions that tested significantly high in concentration. Through these processes the water would become safer for our children without the harmful nitrate ions and the discolored water would become clear. I believe that we should take action as quickly as possible to get our water supply in quality condition for our residents.
Ion exchange and In-situ methods are both effective processes to eliminate ions from the water supply. Iron and Manganese ions that cause the water to be discolored can be removed easily through the in-situ method. And the harmful nitrate ions could be removed through ion exchange. I believe that all three ions are causing problems and should be removed from the water supply. Both processes would benefit our town greatly and think they both should be considered carefully.
Using both methods helps our townspeople tremendously. The processes rid the water of discoloration and of harmful nitrate ions that can cause infants and pregnant women to become ill. There is no potential harmful side effect of either of the methods, though they may not be quite as cost efficient as we would prefer. My course of action does not rid the water of sulfides or zinc, which are both high in concentration. But I believe that it is very important to remove the iron, manganese, and nitrate ions first, because they were the main cause of the declining water quality.
Citations:
"Removing Dissolved Metal: Topics by Science.gov." Removing Dissolved Metal: Topics by Science.gov. N.p., n.d. Web. 19 Mar. 2014.
Removing nitrates with ion exchange. (n.d.). Retrieved from http://www.watertechonline.com/articles/removing-nitrates-with-ion-exchange
Nitrates in Drinking Water. (n.d.). Retrieved from http://www.ext.colostate.edu/pubs/crops/00517.html
