This preview shows page 1 - 2 out of 3 pages. Subscribe to view the full document. I cannot even describe how much Course Hero helped me this summer. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero. CHM Soft Water Hard water is water that has a high mineral content versus soft water which is the absence of calcium, magnesium and certain other metal cation found in hard water and only contains sodium.
This happens when the water comes in contact with rocks or soil. In the United States, 85 percent of the water is hard, according to a U. Geological Survey. So it comes down to this: very soft water can make it hard to rinse yourself; very hard water can make it hard for you to clean yourself. So somewhere between these extremes you can find an optimum middle ground.
Many municipalities apparently do in fact accomplish this with their water treatment plans. It doesn't take soap to make suds, which can take on monumental proportions under some circumstances. In nature, of course, they are known as foam. On December 29, , in Cleveley, a seaside town near Blackpool in the U. These molecules, mixed in with those of H 2 O, kept the latter from forming hydrogen bonds??? Normally when water is vigorously stirred, as this water was by the wind, bubbles form around these pockets of air, but they quickly pop as the air molecules swiftly break through the outnumbered H 2 O's hydrogen bonds.
When the H 2 O is mixed with heavier molecules, the air becomes trapped, though its pressure against this mixture of molecules causes them to form more stable bubbles. No discussion of public water softness is complete without a discussion of water softeners. The public water quality issue is actually much more complex because 1 some water is naturally hard, i. This is not to say that municipal water treatment plants use water softeners they don't ; however, some of their input wastewater has been treated with water softeners by residential and commercial customers and water treatment at the plant necessarily involves removal of enough of these contaminants to meet any relevant state and federal regulations at the minimum.
For example, the city of Paso Robles, CA was motivated by the size and expense of this task to devote a page on its website to educating its residents about how to reduce the "discharge of salt brines into the wastewater collection system" by moderating and altering their use of water softeners The implication here is that, in the absence of sufficient regulations or oversight, a less conscientious city might decide to cut its water treatment costs by skimping on the processing of these discharges, thereby softening the water it provides its citizens.
Where does all this salt come from? One method of water softening is ion exchange 25 , where introduced cations elements that tend to lose electrons rather than gain them in chemical reactions with low ionization potential displace others with greater ionization potential. This is an equation describing a reaction produced by a water softener designed to remove calcium sulfate CaSO 4 , a common well water mineral, using the salt sodium carbonate Na 2 CO 3 20 :.
This is made clearer by specifying the phases of the reactants and products:.
In reality, this is just a bunch of ions except for the CaCO 3. The harder the water, the more sodium is released into it, and the bigger the water disposal problem. How does this work on an atomic level? Group I metals, e. On the other hand, Group II cations, e. The less the ionization potential, the smaller the chance that an "insoluble" relatively speaking compound such as CaCO 3 will form. That explains why sodium and potassium ions are preferred to calcium and magnesium, and introduced to replace them: they are less likely to form troublesome precipitates.
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There is concern about the safety of the ion exchange water-softening process 26,27 because extra sodium and potassium intake in drinking water can upset one's electrolyte balance and in the case of sodium aggravate high blood pressure. In California, one city is taking the first steps toward restricting the residential and commercial use of sodium-based ion exchange water-softeners to reduce groundwater salinity And one North Carolinian claims that some such sodium-softened water kills houseplants There's a funny relationship between the hardness of household water and the pH of the rainwater by definition, mineral-free and therefore extremely soft that it was originally.
And we know that a popular indirect measurement of water hardness is the CaCO 3 concentration mg of precipitated CaCO 3 per L of water in that water So if there's an excess of CaCO 3 in the water after the CO 3 2- has all been "used up," that calcium won't be figured into the hardness measurement. So what this measure is really giving us is nuisance hardness.
So the higher local CO 2 emissions are, the more problematic a certain degree of existing water hardness is and, by extension, the greater the motivation of affected people to use water softeners. There is considerable regional variation within the US for acidity of rainwater and water hardness, incidentally. One extreme case is part of Ohio, where water hardness is high, i.
So if people in this part of the country use enough water softeners to achieve complete softness, that would mean a lot of salinity in their wastewater. On the other hand, North Carolina water is very soft, i. Yet a trip to my local hardware store invariably means getting to see piles of large bags of table salt NaCl for sale for use in water softeners! Another method of water softening is adding EDTA 31 , an amino acid that performs chelation on all metal ions, i. EDTA is not absorbed by the body, but is indirectly capable of causing environmental pollution: disposing of it safely requires special measures that are prescribed by government organizations, since it needs to be treated with sodium to release the minerals it is bonded to.
Hazards 32 are known in detail. It's worth noting that the only use of EDTA and other chelating agents in standard allopathic medical practice is for intravenous treatment of acute heavy metal poisoning in adults However, its use is promoted vigorously online as "chelation therapy" for a variety of ailments It seems to be common sense to me that the benefits of its FDA-approved uses would not carry over to those other uses because 1 chelating agents each remove a wide range of minerals from the body, 2 in the case of acute heavy metal poisoning, most of the metal removed would be the target toxic metal and 3 this therapy would be short-term and the patient would suffer only temporary and presumably moderate essential mineral deficiencies as a result.
There really isn't a standard wastewater processing step designed with salt brine discharges in mind. So these discharges do present problems during an early stage of wastewater processing, when dense solids sludge are allowed to settle on the bottom of large containers known as "sedimentation tanks," while the less dense lipid-containing compounds scum rise to the water surface.
Scrapers on the bottom of the tanks deliver the sludge to a hopper through which it's selectively removed. The remaining water is sent to drainfields that are one to three feet above the groundwater table to be treated, where microbes in the soil break down the remaining chemicals as the water soaks down through the soil, eventually entering the groundwater.
When the sludge completes treatment, it is either compressed into pellets and sold as fertilizer or delivered to landfills. Any sodium entering the system, then, is returned to the environment The problem with salt brine hydrated sodium, i. If sludge sodium is not disposed of properly, that sodium and its companion anions can also cause calcium- and magnesium-displacement problems in the soil.
Alas, you won't see any footnotes here, because what is all theoretical really, hypothetical on my part.
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These units then get in the way when calcium and carbonate ions try to get together to produce CaCO 3 just as CaCO 3 gets in the way of soap joining water as described above, thereby giving hard water its bad reputation for interfering with cleaning, an issue, of course, apart from that of producing limescale. With less CaCO 3 , the water would be softer.
You might be wondering at this point: how do washing machines get clothes clean and rinsed with soft water when you can't get anywhere with your own skin, even with a washcloth? You'll notice that some settings will allow you to wash in warm or hot water, and rinse in cold water. Unless you're washing cotton clothes that haven't been pre-shrunk an increasingly common phenomenon these days , picking the "warm" wash and the "cold" rinse is the ticket for soft water, in my humble opinion. Granted, you probably couldn't stand the cold water the washing machine uses, but tolerably cool water still can make a big difference, and you can get used to it by lowering the temperature gradually.
In the same vein, using cool enough shower water gets the soap to come out of the soap-water solution. The reason for this is that, for solutions to form, bonds in this case, intermolecular ones need to be made, and this requires additional energy. Heat adds energy, providing the energy for these bonds. Similarly, cooling the solution removes energy, resulting in the loss of the bonds. It is generally accepted that hard water shortens the life of washing machines and clothes alike because of the CaCO 3 deposits and those of some other minerals it leaves behind One set of guidelines proposes having separate water systems: hard water for drinking and soft water for washing clothes There are some significant drawbacks to implementing this plan, in addition to the effort and expense of installing and maintaining personal and commercial water softeners.
As stated above, using standard water softening methods involves adding sodium to the water. If you have water that's too soft for your tastes, it probably is just right for your washing machine and you can cope to some degree by rinsing yourself in cool water. We have yet to find a solution that provides optimal comfort, minimizes wear on washing machines and is safe for the environment. One thing we can do now as a group is to make sure that people have a genuine choice about whether water-softening chemicals get into their water. Public wastewater treatment plant personnel can be open about how big the water softener output treatment problem is and to make an effort to educate customers about how water softener use can contaminate groundwater and what they can do to minimize the harm their households inflict on it.
Part of that education should include informing them about the actual hardness of the water in their region and, by implication, how much softening their water really needs to produce a significant reduction in wear on their washing machines and clothes.
There are, of course, kits available to test one's own water. If a lot of sodium leaves the water softener system to enter the sewer system, that suggests it's wasted. Modifying available technology to recycle the sodium would help. One obvious method would be to reduce the water temperature to near freezing, but that would be expensive.
Or we could go back to what we learned in elementary school: have the water stand in a tank with strings hanging down in it so that salt crystals form and recycle the salt crystals afterwards. However, this system would work only if softened water were used only in washing machines and dishwashers, which use much less water than people do taking showers. Part of the municipal solution might involve charging more for wastewater processing, with the individual household cost being set according to the sodium concentration in that household's or, more realistically, neighborhood's wastewater.
But this would be more effective if customers can be convinced that their need for water softeners is less than they had previously assumed. In the long term, we as a nation may need to come up with new water-softening technologies that take minerals out of the water instead of putting more in it. But in some communities, mine among them, this really doesn't seem to be a pressing problem. Finally, reducing CO 2 emissions will reduce the need for water softening since it will reduce the amount of CaCO 3 and calcium stearate produced.
But that's obviously a very long-term goal!
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CRC Press. Guidelines for Canadian Drinking Water Quality. State of Minnesota, "Sulfate in Well Water". III: studies with mixed micelles. Ball, P. Shakhashiri, B. Field and Swamp: Animals and Their Habitats. Abstract Very soft water can be difficult to bathe with because when it's mixed with soap it's hard to remove but feels "soft! Introduction Maybe Shakespeare got his inspiration for Macbeth's wife's "Out, damn'd spot! Here is why: Very hard water vs. Natural Sudsiness It doesn't take soap to make suds, which can take on monumental proportions under some circumstances.
Water Hardness, Water Acidity and Water Softeners No discussion of public water softness is complete without a discussion of water softeners. The Impact of Water Softener Saline Discharge on Individual Households Alas, you won't see any footnotes here, because what is all theoretical really, hypothetical on my part. References 1. Solution Wikipedia 2.
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