Raising Awareness of Water Issues - American Chemical Society

Chapter 2

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Raising Awareness of Water Issues: The Education Connection, the Educational Potential Shelby Maurice and Mark A. Benvenuto* Department of Chemistry and Biochemistry, University of Detroit Mercy, 4001 W. McNichols Road, Detroit, Michigan 48221-3038 *E-mail: [email protected].

The challenges posed by finite amounts of clean, potable water and a continuously growing human population are still not well understood by a significant portion of that population. An increased awareness of water issues, specifically of waste water treatment technologies and sanitation practices, can be attained if these issues are addressed thoroughly and repeatedly in general chemistry classes at both high school and college level, and in upper level undergraduate chemistry curriculum courses such as industrial chemistry and environmental chemistry, as well as engineering classes. This chapter presents a detailed, mapped approach to raising the awareness of current water issues by repeated exposure in college chemistry classes in several different courses.

Introduction Water may be the single most important chemical for the propagation of life, if one considers all aquatic life, including deep sea organisms – although one might argue air is equally so – and it is certainly the material that humankind has chosen to live next to for all of known history. Living near salt water as well as fresh water has provided humans with food, with drinking water in the case of freshwater lakes, rivers, and streams, and with a means of moving ourselves and heavy objects, once we had discovered how to build boats. The human population explosion that has occurred in the twentieth century though has put strains on water supplies that have not occurred at any other time in history (1, 2). The sheer number of people living © 2015 American Chemical Society In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

on or near water, and the construction of numerous dams across major and minor rivers mean that existing water resources are stressed more severely than they have been at any other time (3). In this environment it becomes imperative for an educated citizenry to understand water issues, and how those issues affect themselves, their local community, and the greater global community. What can be called ‘water education’ can be built into the chemistry curriculum at several levels (4–13).


The Issues: Water Treatment Technologies There are several well-established means of purifying water of soluble, slightly soluble, and insoluble contaminants. It is generally agreed that desalination, waste water treatment, and conservation are the three categories into which all water purification falls, with desalination being the most expensive, waste water treatment such as sewage clean-up second, and conservation efforts the least expensive of the three (3, 4). Desalination There are several different methods of desalination of sea water or brackish water. A partial, but non-exhaustive list of them includes: i. Reverse osmosis ii. Multi-stage flash distilling – roughly 75% of operations iii. Membrane distillation iv. Electrodialysis reversal v. Nano-filtration vi. Ion exchange vii. Solar desalination viii. Freezing desalination By far the most common is multi-stage flash distilling in which some amount of saline or brackish water is heated rapidly – flashed – and the condensate collected, resulting in pure water. By repeating the flashing process numerous times, large amounts of clean water can be collected, while the more saline fraction of the water is returned to the source. Desalination efforts can be performed on a small scale, such as in the rescue and emergency kits of recreational boaters. But enormous amounts of water are desalinated through industrial-scale plants in various countries, or off their coasts. Israel, Singapore, and Venezuela all have large desalination plants that serve their populations. Sewage – Waste Treatment Waste water treatment and sewage treatment often mean exactly the same thing in terms of chemical purification and re-concentration of water. While the 28 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

steps in any reclamation process differ based on the starting aqueous mixture, there are several common, broad steps that all waste water must undergo for treatment and clean-up. i.

ii.


iii.

iv.

v.

vi.

vii.

Pre-treatment: This is the removal of macroscopic wastes from an incoming water stream. This includes yard waste in many municipal areas, as well as pieces of litter and other objects. Primary treatment – settling: This involves allowing smaller particulate matter to settle to the bottom of tanks, thus clearing the water further, usually at very low cost. Fat and oil removal, if necessary: This is simply the removal of non-aqueous liquid material, either through mechanical means such as skimming, or through chemical means such as encapsulation by surfactants. Secondary beds – microbial digestion: This step involves the removal of microscopic and in some cases such microscopic materials by beneficial microbes. Chemical addition, chlorine: The addition of chlorine to reclaimed water is imperative when the water will be re-used by people. The chlorine serves as a thorough and yet inexpensive anti-bacterial shock. Settling beds/ponds: This step can occur before the addition of chlorine, but is designed to be a final physical separation of any foreign materials from the water. Discharge to local waters

Importantly, any combination of these steps is usually less expensive than the desalination of sea water. This is a matter of the cost of the energy involved in desalination, in pumps to force water through membranes, in the cost of the membranes, and in the cost of the electricity to run such operations. While there are some costs involved in sewage and waste-water treatment, the uses of settling ponds and microbial digestion often mean cost savings in comparison (5, 14, 15). Water Conservation The third of the three broad categories when it comes to water purification and use – conservation – is by any and all measures the least expensive. This is because it essentially involves doing nothing but maintenance on already existing systems. Being aware of and fixing leaks in the system, from water mains all the way to the consumer and home tap leaks is much more a matter of improving the behavior of users than it is a matter of the chemistry that is involved in separating water from salts or other pollutants. In areas where population density is high, and there is the belief that people will not change voluntarily, systems of tax incentives as well as punishments have been used effectively to conserve water. This often means lowering taxes on consumers and businesses that show less water use in monthly summaries, as well as police actually fining residents for wasting water, such as watering suburban lawns on what have been designated ozone alert days (which now occurs in several municipalities in the United States). 29 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


Remaining Materials – Organics, Such as Pharmaceuticals One current issue with water chemistry and purification, one that is gaining a certain amount of notice, even in the common press (3–5, 15–20), is that of pharmaceuticals that remain in water even after treatment in water and sewage treatment plants. Essentially, pharmaceuticals are active organic molecules that are designed to be relatively stable in water – since humans and animals that ingest such materials are themselves mostly water – and sewage treatment plants have never been designed to neutralize such materials. The end result is that pharmaceuticals which have been urinated or excreted into toilets, passed through animals and into their waste materials, or that have been disposed of in toilets on purpose, as a way to keep them from garbage cans and the supposedly prying hands on small children, enter our waterways and our larger environment, essentially untouched and still active. While a chemical solution to this problem does not yet exist, this issue is certainly one that can be brought into the classroom for discussion and for raising awareness.

Water in the Curriculum General Chemistry Content The content of general chemistry textbooks has not changed markedly for the past several decades (21–24). Numerous textbooks cover the following subjects, and when they are aimed at students who are science and engineering majors, usually treat these topics in considerable detail: a. b.

Salts, nomenclature, ionic materials Reactions in solution, in water i. The basis of stoichiometry ii. The basis of redox and electrochemistry iii. Applications: from human health to battery-powered automobiles

c. d.

Heat capacity, water versus other liquids, and versus metals Solutions, concentrations, molarity i. Water as solvent, water as solute ii. The light-hearted, water as a component in mixed drinks

e. f. g. h.

Molecular structure, polarity, hydrogen bonding and water Colligative properties, including the vant Hoff factor Chemical equilibria, water as organic by-product Acid – base chemistry, pH and such measurements in water

In each of the above topics, it is not particularly difficult to focus on how the water can be the main theme behind the concept. In several of these cases, the chemistry involved is utterly dependent on water. 30 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


Choosing just one example from the above list, “molecular structure, polarity, and hydrogen bonding,” a very simple experiment that can easily be run in the first semester freshmen chemistry laboratory is the mixing of several different amounts of an alcohol such as ethyl alcohol and water, and graphing the resultant volumes. It should be obvious that 50 mL of one liquid or the other is 50 mL. However, when the proportions are changed – 45 mL ethanol added to 5 mL water, then 40 mL ethanol added to 10 mL water, and so on, until a mixture of 25 mL of each is combined, the sum volume is never 50 mL. The largest deviation that students find tends to be the 25:25 mL mixture, which combines to form a 47.5 mL total volume of solution (within reasonable error, using standard graduated cylinders for measurement). This is an easy example of a means to show how hydrogen bonding affects a macroscopic measurement, volume. Likewise, numerous reactions in the first year of a general chemistry course involve the production of water. Indeed, understanding solubility and insolubility often includes the discussion of acid and base combinations that produce water, and note that it is the production of water that drives the reaction, by removing ions from solution. As well, the basic understanding of molarity and molality can be one in which the amount of materials, usually solids, dissolved in water is the main topic of discussion. Numerous teachers have asked students to compute the molarity of seawater, or have provided data so that the concentration of some material in water, often pollutants, can be computed. In short, every item listed above has some equally straightforward experiment that can utilize water, and thus raise student awareness of water chemistry.

Environmental Chemistry Content The technologies we have already discussed: desalination, sewage clean-up, and conservation are almost impossible to omit from an environmental chemistry class. Such classes usually discuss water pollution in considerable detail. For example, the processes for water desalination that were just listed indicate that multi-stage flash distilling is the major means by which water is desalinated. This is also an energy intensive operation, and this point can be the beginning of an in-class discussion on energy as part of a chemical equation. Such a discussion can also focus on the fact that it is energetically and economically more favorable to clean up once-used water, also called grey water, with settling ponds and microbes than it is to desalinate sea water. Thus, this example can serve to initiate a discussion and increase understanding for students in an environmental chemistry class. But this could also be applicable in a basic biochemistry class should microbial clean-up of water be the focus of the discussion. Additionally, this point can be used in first semester physical chemistry classes when energy is the aspect of water purification being examined. An easy off-shoot of the larger subject of water in an environmental chemistry class is the water cycle in local areas. This is both straightforward and easy to use to bring home for students the importance of water and water chemistry, since it affects them and their families (19). 31 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

Industrial Chemistry Content


The production of water, discussed above, is a subject often covered in industrial chemistry classes, simply because clean water is required for numerous large-scale chemical processes (25). Water use in the following processes is all performed daily on a massive basis: The Chlor-Alkali Process. This produces sodium hydroxide, elemental chlorine, and elemental hydrogen according to the following reaction:

All three products are used profitably, and water is a reactant as well as the solvent for the process. The Solvay Process. While Na2CO3 production is the main product, and the reaction chemistry can be shown simply as follows:

The process is much more complex and intricate, and importantly it requires water again as both reactant and solvent. The Frasch Process. Elemental sulfur is still extracted from underground deposits in some parts of the world using s triple tube assembly that forces superheated water into the sulfur deposit to force it to the surface. While there is no reaction chemistry to accompany this, water is essential to the process. The Contact Process. This method of sulfuric acid production requires water once again both as reactant and solvent. It can be outlined in five reactions.

It can be noted when discussing this chemistry that simply trying to “stop” the process at the third step and attempt direct addition of sulfur trioxide to water is never done on a large scale because it produces a corrosive aerosol mist. The Ostwald process. The production of nitric acid is another absolutely huge piece of chemistry, one that is probably taught in all industrial chemistry courses. The three general reactions that define it again require water. They are:

Here we see that water is both a product and at a later step a reactant. Additionally, the use of water in the final step produces more nitrogen monoxide, which is used to perpetuate the reaction. 32 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


The Washoe Process. This method of producing silver is not one that lends itself easily to reaction chemistry, but steam is required to heat the ore – mercury amalgam, and ultimately to isolate silver metal. Pulp and paper production. This is another example in which an industrial process utterly depends on water. Almost every step of the pulp and paper making process requires large amounts of clean water, and even though it is not possible to present chemical equations that show neatly how it is used, the production can not be accomplished without it. Mining operations and water. The term “mining” implies digging holes in the ground and putting men and machinery into them to extract some material. However, this has become something of a misnomer, as solution mining is now used for several water-soluble materials, such as the just mentioned sulfur, and especially for potash. In such solution mining operations, hot water is injected into the mine, the potash is solvated, and the brine solution is extracted. This is an example of a very large-scale water use for western Canada, where such mines are located. Oil refining and fracking. The discussion of what get called “fracking fluids” has become part of what is reported in the national and local news, usually in relation to some odd or exotic chemical used in the mix. But an understanding of fracking fluids means the awareness that most of any fluid mix is water. This means a great deal of water is needed for such operations, and also means that some way needs to be found to separate the water from the other materials whenever it is returned to the surface above the fracking site.

Incorporation into the Curriculum In General Chemistry In any general chemistry class, several opportunities can be taken to emphasize water at every point of discussion. Water can be the thread or theme that connects numerous concepts throughout the entire course. As well, general chemistry is taken by a relatively large number of students, certainly of science and engineering students. Three examples that utilize water extensively follow. Scaling up. Reaction chemistry examples do not have to be in grams or milligrams. They continue to be at this scale for no reason other than this is the general range of balances in teaching laboratories, to which many general chemistry classes are connected. But it is quite easy to scale up a problem in which some reaction is run in water and a product is formed (silver nitrate, for example) from grams to tons, and to determine how much water would then be needed. Emphasis on human health. A large number of students enter colleges and universities with the plan to graduate and then attend a medical, dental, veterinary, or some other health profession-related school. Tying together the idea of access to clean water, its consumption, and its use brings the chemistry being taught to life by making it immediately relevant. The subject matter is no longer simply material to be memorized. It is information and knowledge that these students will need and will use in their next educational undertaking. 33 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

Water and current quality of life. It is not difficult to make connections between chemical products that are made today, and the water that isolates or produces them. The fields in which medicines, refined metals, plastics, and fertilizers will be used may seem wide (and scattered) to students, but water in one substance that connects them all. This can be a very useful “hook” as a teaching tool.


In Organic Chemistry In the traditional curriculum, organic chemistry remains the major chemistry course of the sophomore year, although numerous colleges and universities have in the past decade moved to a model in which some organic chemistry is taught in the first year, while subjects such as equilibrium, entropy, and kinetics are moved to the second year. But wherever it falls, the organic chemistry course can serve as a course of study in which one can emphasize where water works as a solvent, and where it does not. Additionally, in this class the instructor can discuss points of water production, meaning often as by-product. These condensation reactions are numerous. A non-exhaustive list includes: a. b. c. d. e. f. g. h. i. j.

Aldol condensation Claisen – Schmidt condensation Darzens condensation Dieckmann condensation Guareschi – Thorpe condensation Knoevenagel condensation Michael condensation Pechmann condensation Schiff’s Base condensation Ziegler condensation

Using just the Schiff’s Base condensation as an example, as shown here, it can be explained that not only is water the reaction by-product, but its formation is the energetic driving force.

The Schiff’s base condensation is a very “forgiving” reaction, in that it can run in numerous organic solvents. But it cannot be run in water or in alcohols that still contain a small percentage of water (such as 96% ethanol). It is the formation of water that drives the reaction to completion, and thus using it as or in a solvent will drive the equilibrium back to the reactants’ side. In Industrial and Environmental Chemistry We have already discussed the numerous large scale processes that require water either as a reactant or as a solvent, or both. In addition to this, past and present incidents can be discussed throughout such a class. This does not need 34 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

to be an eternal litany of spills. On the contrary, such negative incidents can be counterbalanced by examples of processes where a secondary product finds a positive use. Additionally, the improvements that processes undergo over the course of time deserve to be noted. An example of this might be how the HCl produced in an organic synthesis, which in past decades might have been discarded, is now captured in water and used in some other process (the pickling of steel and other metals accounts for slightly more than half of all HCl produced today).


Conclusions This chapter has outlined several points where water can be used in the chemistry curriculum to prove some learning point. Water is not only a common material, it can serve as a common example in general chemistry, organic chemistry, environmental chemistry, and industrial chemistry classes. Its structure, properties, and reactivity can be an educational focus at several points in each of these classes. Constant reinforcement of water chemistry and its many uses develops awareness of water’s abilities and limitations in students. All the points that have been discussed are quite easy to incorporate in the classes mentioned, which can make water a recurring, and oftentimes central topic in the curriculum.

References 1. 2. 3. 4.

5. 6.

7. 8. 9.

Saline Water Conversion; ACS Advances in Chemistry Series 27; American Chemical Society: Washington, DC, 1960. Saline Water Conservation – II; Gould, R. F., Ed.; ACS Advances in Chemistry Series 38; American Chemical Society: Washington, DC, 1963. Letter Report Assessing the USGS National Water Quality Assessment Program’s Science Plan; National Academies Press: Washington, DC, 2011. Letter Report Assessing the USGS National Water Quality Assessment Program’s Science Framework; National Academies Press: Washington, DC, 2010. Urban Stormwater Management in the United States; National Academies Press: Washington, DC, 2009. Nutrient Control Actions for Improving Water Quality in the Mississippi River Basin and Northern Gulf of Mexico; National Academies Press: Washington, DC, 2009. Water Contamination Emergencies: Can We Cope? Thompson, K. C., Gray, J., Eds.; Royal Society of Chemistry: London, 2004. Water Contamination Emergencies: Enhancing Our Response; Thompson, K. C., Gray, J., Eds.; Royal Society of Chemistry: London, 2006. Water: The Power, Promise, and Turmoil of North America’s Fresh Water. National Geographic 1993 November. 35 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.


10. Gorbachev, M. Water: The Globe’s Most Precious Resource, the World’s Most Pressing Problem. Civilization, A Special Section 2000 October/November. 11. Water: Our Thirsty World. National Geographic 2010 AprilA Special Issue. 12. Troubled Waters: Are We Emptying the Oceans? Virginia Quarterly Review 2011 Summer, 87 (3). 13. The Future of Fish. Time 2011 July18, 28–36. 14. Particulates in Water: Characterization, Fate, Effects, and Removal; Kavanaugh, M. C., Leckie, J. O., Eds.; ACS Advances in Chemistry Series 189; American Chemical Society: Washington, DC, 1980. 15. Environmental Chemistry of Lakes and Reservoirs; Baker, A., Ed.; ACS Advances in Chemistry Series 237; American Chemical Society: Washington, DC, 1994. 16. Harvard Medical Advisor, Pharmaceutical and Personal Care Products. The Detroit Free Press 2011 July3, D4. 17. Utah Waterways Test Positive for Prescription Drugs. KSL TV (accessed 29 April 2015) http://www.ksl.com/?nid=148&sid=3959442. 18. Area Tap Water Has Traces of Medicines. The Washington Post 2008 March10, B01. 19. Detroit Water Dept. Must Reorganize to Survive. DBusiness, Annual 2014 (accessed 29 April 2015) http://www.dbusiness.com/Blogs/Annual-2014/ Detroit-Water-Dept-Must-Reorganize-to-Survive/. 20. It’s All in the Water: Studies of Materials and Conditions in Fresh and Salt Water Bodies, Benvenuto, M. A., Roberts-Kirchhoff, E. S., Murray, M. N., and Garshott, D. M., Eds.; ACS Symposium Series 1086; American Chemical Society: Washington, DC, 2011. 21. Partington, J. R. Text-Book of Inorganic Chemistry; MacMillan & Co., Ltd.: London, 1933. 22. Brown, T. L.; LeMay, H. E., Jr. Chemistry: The Central Science; PrenticeHall: New Jersey, 1977. 23. Masterson, W. L.; Slowinski, E. S. Chemical Principles, 4th ed.; W.B. Saunders Company: London, 1977. 24. Brady, J. E.; Senese, F. Chemistry: Matter and Its Changes, 5th ed.; John Wiley & Sons, Inc.: New Jersey, 2009. 25. Benvenuto. M. A. Industrial Chemistry; DeGruyter: Berlin, 2014.

36 In Water Challenges and Solutions on a Global Scale; Loganathan, et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2015.

Raising Awareness of Water Issues - American Chemical Society

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