When we examine the sustainability profile of a particular community, we always have to look at the water system that sustains that community. Historically, people dwellings were associated with the sources of water: rivers, springs, or lakes. In modern times, the issue of water remains primary. We have more advanced technologies to extract and distribute water resources, and we have other technologies to utilize and treat water. Those technologies become key links in the universal water cycle, which involves both ecological and anthropogenic spheres. This lesson specifically focuses on the technological methods to provide efficiency for water supply and further to provide sustainability of water resources. Such technologies target the two growing problems - water resource depletion and water pollution. After touching on the background of water management systems, this lesson will direct you to the examples of lifecycle analysis, which helps identify the technologies with the higher promise for sustainability.
By the end of this lesson, you should be able to:
These articles are available online through PSU Library system - See the "Library Resources" / E-Reserves link in Canvas.
If you have any questions while working through this Lesson, please post them to our Message Board forum in Canvas. You can use that space any time to chat about course topics or to ask questions. While you are there, please feel free to post your own responses if you are able to help out a classmate.
Water is often envisioned as the bloodstream of biosphere. It is a universal medium that is crucial for sustainability of both ecological and human societies. There is no substitute for water. More than 70% of the earth surface is covered by water. However, only 3% of this reserve is fresh water that can be used for human consumption. 90% of the earth's fresh water resources is contained in groundwater and ice, and only 10% is water is contained in surface reservoirs - rivers, lakes, wetlands, and streams. [Girard, 2013].
Although sustaining life is one of the main key purposes of the water, present-day agriculture and many industry branches heavily rely on the abundance of the water resource. For example, water is used as heat transport fluid in thermoelectric energy systems, such as nuclear and fossil fuel fired power plants and concentrating solar power farms. It is used as solvent and raw material in chemical manufacturing. Mining industry utilizes significant amount of water in hydraulic fracturing and oil recovery. Those industries are important parts of modern infrastructure; hence, the water demand must be met to keep the power and food production at the necessary level.
To plan sustainable utilization of water resources, we must understand how the water cycle works at the global and local scales. The amount of water on earth is finite, and the natural water cycle is a system that controls the circulation and redistribution of that resource. You must be familiar with the water cycle concept from your early science classes. But you can get a refresher from the following short video:
This quite general and deceivingly simple concept of water cycle has a number of limitations which are important to understand:
To add some quantitative information to the picture, please take a look at the US Geological Survey (USGS) [7] website.
If you scroll down and click on any of the components of the water cycle, you will get comprehensive information on that reservoir. Note the dramatic difference in water capacity of different reservoirs. Try to remember at least the order of magnitude of the specific water reserves, since such quantitative perception can be quite useful in sustainability analysis.
Annual evaporation from the ocean is about 80,000 cubic miles versus 15,000 cubic miles from the land. Given the amounts of water evaporated and precipitated are almost equal, the total amount of water exchanged between the atmosphere and the earth surface is about 95,000 cubic miles. Out of the water evaporated and then returned by rainstorms, 24,000 cubic miles fall on land as precipitation. The average annual precipitation over the land is 26 inches, but it is not evenly distributed. Arid locations may get under 1 inch of precipitation, whereas some others can get more than 400 inches. The total annual precipitation in the United States is about 30 inches per year, which accounts for about 4300 billion gallons per day. The total water flow from surface and subsurface sources is about 8.5 inches per year, i.e., about 1200 billion gallons a day. This amount is available for human use, including domestic, industrial, agricultural, and recreational use. Considering that the difference between precipitation and stream flow is -21.5 inches per year (3100 billion gallons per day), this amount is assumed to return to the atmosphere (through evaporation and transpiration). This returned volume roughly accounts for 70 % of the total water supply. [Source: USDA [8], 2001]
In nature, the hydrological cycle is well-balanced, and fluctuations of environmental water stocks are reversible. But when some of the parts of the system are interfered, resilience of the system may be jeopardized. This can happen when the anthropogenic water consumption cycle is plugged in to the natural water cycle. The main troubles currently experienced because of mismatch of the anthropogenic and natural cycles include:
While the above-listed factors may have acute local effect, recent research also shows that large-scale hydraulic engineering produces global-scale impact on the earth's water cycle, raising the global sea level.
Read through the following article that discusses the main man-made factors that affect the natural hydrological balance. While you are welcome to read the whole article, put the main focus on Table 1, which quantifies those effects, and sections on "Major classes of water engineering" and "Impacts of Human control...", which explain the specific mechanisms within the cycle.
Journal article: Vorosmarty, C.J., Sahagian, D., Anthropogenic Disturbance of the Terrestrial Water Cycle, BioScience, vol. 50, pp.753-763. (Full article can be accessed via Library e-Reserves in Canvas.)
Some of the things to reflect on in this reading:
The idea of sustainability in water management implies matching the natural water cycle and technical (anthropogenic) water use cycle together with minimal damage and maximum mutual support. A new approach to integrated managing water resources is known as total water cycle management, where water supply, stormwater, and wastewater are all considered during the design process.
The diagram in Figure 6.1. presents the water cycle in terms of stocks and flows. It illustrates the connections between different natural processes and reservoirs and also introduces the anthropogenic water paths into the system. The diagram is quite busy, so it would be useful to walk through it step by step. The video embedded below provides commentary to different parts of the diagram and also shows the links where water-treatment technologies must be applied to provide compatibility between the environmental and anthropogenic spheres. While watching, you may need to switch to 'full-screen' and HD quality setting to better see smaller details.
Click on the image to view the large version
As you can see in the diagram in Figure 6.1, the boundaries between the natural and human-controlled water systems are where the sustainable water treatment technologies should come into action. The bottom line is that the role sustainable water technology is to reconcile the natural and anthropogenic cycles and to alleviate mutual harm and system misbalance.
The following list gives you some examples of possible actions that help to keep combined water system sustainable (can vary with location):
Water regime management
Water quality
Water conservation
Water value
Many of these actions require efficient technologies of water control and water treatment. The following sections of this lesson provide you with some examples and technical details on current practice of water treatment and prospective technologies for the future.
Which of the following continental water storage reserves has the largest global capacity?
Click for answer.
What processes in the water cycle are responsible for depletion of continental water storage?
Click for answer.
When water is extracted from the natural water cycle, where does it go?
Based on government statistics, a big part of it (~40%) is used for agricultural needs (e.g., irrigation for crops or livestock), around 47% is used for industrial needs (e.g., power generation, mining, etc.), and around 13% is going to public supply (e.g., domestic or commercial) (Figure 6.1). However, these numbers can vary with location. For example, in Minnesota, the majority of the water extracted is used for power generation, while in California, the dominating use is irrigation [USGS, 2015 [10]].
Although residential water consumption accounts for a smaller fraction of the whole, domestic water economy is considered an important factor in urban sustainability. The overall domestic water use is expected to grow as world population grows.
According to the U.S. Geological Survey 2015 water census, daily per capita domestic water use in the U.S. was 82 gallons per day, which was an improvement from 88 gallons per day estimated in 2010 census, and 101 gallons per day in 1995 census. This value represents the national average, and the actual local water use can vary broadly - for instance, from 35 gpd in Connecticut to 186 gpd in Idaho [USGS, 2015 [10]].
Typical US home water use accounting is:
One can estimate how much water they use at home with some simple online calculators:
As the population grows, so does the stress on available water resources. Hence, there are a number of water conservation strategies, with some of the most intuitive approaches being:
Sustainability goals and growing demands for clean water require new solutions in water conservation and use. There are technologies in place; however, many existing methods sometimes have low efficiency and are prone to water losses. Some innovative approaches are overviewed in this Guardian article: "The new water technologies that could save the planet [15]."
The technologies mentioned in this article work out a number of issues, such as scalability, cost, and efficiency. In sustainable development, we want the systems to be affordable and compact, not using too many resources. That makes them easy to implement in both urban and rural settings.
US EPA introduced a set of strategic practices and policies to water promote water conservation. There are three levels of control, which are summarized in Table 6.1 below. Level 1 measures represent the most basic practices, Level 2 measures are intermediate-level controls, and Level 3 lists more advanced strategies for water conservation. When organizations design their water conservation programs, they may start at Level 1 and gradually proceed to Levels 2 and 3:
Level 1 Measures | Level 2 Measures | Level 3 Measures |
---|---|---|
Universal metering | Water-use audits | Replacements and promotions |
Water accounting and loss control | Retrofits | Reuse and recycling |
Costing and pricing | Pressure management | Water-use regulation |
Information and education | Landscape efficiency | Integrated resource management |
Complete the following reading assignment to learn what each of the above-listed measures involves.
The following EPA document will help you to understand the key strategies and driving forces in water demand management and water conservation.
USEPA Water Conservation Plan Guidelines, EPA 1998, Appendix A: Water Conservation Measures [2], pp. 143-155.
While reading, look through the definitions of the terms listed in the above table and understand them. Implementation of these measures has triple leverage: economics, policy, and technology. As you read, particularly think about the role technologies may play in the effectiveness of these measures.
This question is based on the above reading.
What kind of technologies would play a role in the implementation of the following measures of water conservation? Fill in your ideas in the blank, then click for answers.
Water reuse and recycling
Click for answer.
Water accounting and loss control
Click for answer.
Landscape efficiency
Click for answer.
Retrofits
Click for answer.
Water treatment technologies are designed to eliminate harmful effects of pollutants and natural substances to human health and environment. Within the blended water cycle (considered on page 6.1), these technologies are often placed at the transitions between the environment and human sphere to adapt the water quality.
For example, when water passes from the environmental source to the human consumption system, there is a possible risk to human health from some natural bacteria, chemical elements. Hence, natural water (from either surface or underground reservoir) needs to be purified to a certain standard. On the other end of the system, the water containing waste or substances resulting from the domestic, agricultural, or industrial activity must be cleaned before returning to the environmental pathways. If this is not done, harmful effects of concentrated pollutants can cause significant disturbance to the natural water ecology and escalate damage to both ecosystem and society in the long run. Some common effects of wastewater pollution include eutrophication (biological nutrient pollution; for example, releasing access of nitrogen and phosphorus —"overfeeding ecosystem"); oxygen depletion (due to oxidation of organic compounds); odor and aesthetic damage; proliferation of harmful bacteria, viruses, fungi in drinking water supply.
Centralized water treatment approach implies treating large amounts of water at large rates in a "central" location and distributing that water via networks of pipelines, channels, and intermediate reservoirs. Centralized water treatment is largely implemented and maintained in major urban areas and in most parts of the developed world. Probably most of us primarily use the centralized treatment in our lives (maybe except some travel circumstances).
A couple of videos below describe large-scale water treatment systems that are designed to remove undesired contaminants from water.
This first video shows an example of how water is treated during its transfer from the environmental source to the drinking water supply:
This second video illustrates the treatment of the wastewater generated by human activity before it is returned to the environment:
As we can see from these videos, the design of a large-capacity water treatment plant is very complex and involves not one but many steps, each of those utilizing multiple technologies. It is not our goal to learn all of them in detail in one lesson. However, should you have a specific interest in this topic, the US EPA Wastewater Technology Fact Sheets [22] web page can serve as a great resource for obtaining more technical information about them.
Depending on the degree of cleaning and purification, treated water can be reused for:
The main concern in water reuse is to meet the water quality requirements for its intended use. Quality requirements are determined by federal, state, and regional regulatory authorities and may vary. The general guidelines by EPA with regards to the effluent from the wastewater treatment facilities are given in Table 6.2 below:
Measures | Effluent Limitation | ||
---|---|---|---|
Daily maximum | Weekly average | Monthly average | |
5-day Biochemical Oxygen Demand (BOD5) | 60 mg/L | 45 mg/L | 30 mg/L |
5-day Carbonaceous Biochemical Oxygen Demand (CBOD5) | 50 mg/L | 40 mg/L | 25 mg/L |
Total Suspended Solids (TSS) | 60 mg/L | 45 mg/L | 30 mg/L |
pH (instantaneous) | 6.0-9.0 | --- | --- |
Here is an explanation of measures in this table if you are not familiar with the terms:
These limits determined by EPA are included in the government regulations, published in the Rules of Department of Natural Resources [CSR, 2014] [23]. This document also contains extensive data on limitations imposed on the contents of the toxic element in water before it is reused or discharged in a certain way to the environment. Check Table A for the maximum tolerated concentrations of metals (p.24) and organics (p. 26). The toxicity requirements are especially relevant to industrial water use.
Chemical tests to determine the above metrics are used as controls at any wastewater treatment plant. Various technologies are developed to improve the treatment efficiency and to produce a cleaner effluent suitable for further use.
Traditional water treatment plants accomplish an important function. However, these facilities themselves produce significant environmental impact by consuming energy, producing emissions, by-products, and waste to be disposed of. Later in this lesson, an example is given for a life cycle assessment study which analyzes the way to make these systems more benign.
One of the trends in improving the environmental profile of wastewater treatment facilities is the design of ecological systems that mimic natural processes of neutralizing the pollution.
Here are a couple of examples of the development of such systems:
These examples show that ecological treatment systems typically work at the small scale being capable to treat liquid waste from a community of 300-1000 people. This makes them attractive for decentralized treatment for secluded autonomous areas.
Decentralized systems of water purification often become technologies of choice in developing countries because they do not require huge infrastructure or can be set up quicker when infrastructure is destroyed. Small-scale technologies provide quick response to urgent needs. There are multiple ways to approach the issue. Here is one of them: watch this 10 min video to see an example how small-scale technology can help solve large-scale problems.
Click on the link below to read about some small innovations that make big difference when applied at the right place at the right time:
6 Water-purifying Devices for Clean Drinking Water in the Developing World [30]
Next, let us get a little bit deeper into the issue. I ask you to read the following paper which analyzes a case study of a decentralized wastewater treatment system in India. It covers enough technical details to understand how the technology works and provides a useful discussion of environmental, economic, and social aspects:
Dhinadhayalan, M., Nema, A., Decentralised wastewater management - New concepts and innovative technological feasibility for developing countries, Sustain. Environ. Res., 22(1), 39-44 (2012). (The full article is accessible via Library e-Reserves in Canvas)
While reading, focus on understanding the pros and cons of the decentralized approach (compared to central distribution system). In your own notes, list three key advantages of decentralized technologies that justify their development and implementation. Also, list three disadvantages that may limit their use in different parts of the world. Can you imagine to use only de-centralized water treatment in your current location? What kind of social impacts might it create?
The BOD is a measure of which type of pollutant in the water?
Click for answer.
Which stages in wastewater treatment are designed to decrease BOD of the effluent?
Click for answer.
Now, as we have a long list and various scales of water treatment technologies, sustainability goals require their careful assessment in terms of environmental, economic, and social effectiveness. LCA analysis is a very common tool to select specific technologies for a particular sustainability system. Note that specific location, hydrological profile, and available infrastructure are pivoting factors in such assessment. LCA cannot be general - it has to be case-specific. Therefore, it would be best for us to consider a specific example that would describe LCA for a particular prospective water treatment technology.
The LCA study referred to below is on a novel membrane-based technology for drinking water treatment. It compares conventional existing practice with a new method using comprehensive lifecycle inventory for both and applying LCA software for data interpretation. This article is a good example to follow when designing an LCA project:
Bonton, A., Bouchard, C., Barbeau, B., Jedrzejak, Comparative life cycle assessment of water treatment plants [31], Desalination 284, 42-54 (2012). (Full version of this article is accessible via E-Reserves in Canvas.)
This article contains a significant amount of technical details and chemistry data, which some of you may find hard to digest. You do not have to understand it all - your goal will be to follow through the methodology and understand the main steps that lead to authoritative conclusions. While reading, pay attention to the following aspects:
This real-life LCA project shows that proper assessment requires a great deal of technical detail and a significant amount of data. As a matter of fact, the authors had to perform an autopsy of system components to enlist all included chemical components with their potential environmental impacts at the stage of system manufacturing. Furthermore, operational data have to be closely tied to the specific demographic and geographic setting and the scale of application.
An additional thought on LCA: The output of LCA is quantified environmental impact, so it is most effectively used to compare alternatives - different products, systems, technologies, or methods. It has much less value when performed for a single product or a single technology since, without a clear reference point (a baseline), it is hard to tell if the impact small, large, or catastrophic, if the alternative brings improvement or makes things worse. Zero impact is probably not a good reference because no such ideal technology possibly exists. LCA also allows identifying the relative magnitude of various impacts. For example, we can determine if there is a particular project has a higher contribution to greenhouse gas emissions or to soil contamination, etc. In turn, this would help direct the mitigation measures - actions to reduce impact by redesigning the system, improving the process, or searching for an alternative.
Here is another example of comparative LCA (in the form of a slide presentation), which is related to three wastewater treatment strategies. This reading is optional, but also provides you with a good illustration of the approach.
Lyons, E et al., Life Cycle Assessment of Three Water Scenarios: Importation, Reclamation, and Desalination [32] (Arizona State University)
Do you remember the main four stages of the technology lifecycle that are typically considered in LCA?
Click for answer.
Do you remember the main four phases of an LCA project?
Click for answer.
This lesson drew some connections between the global water resources and human needs for water. With the fast-growing population and fresh water needs, the balance in the hydrologic cycle and pollution of water resources become critical issues. While there are technologies in place to adapt natural water for human use and to adapt the human-used water for environmental use, their capacity and effectiveness are not always sufficient. Water conservation and reuse are other important strategies to complement the combined water cycle. Sustainable water management implies the systematic approach to the water resources and considers anthropogenic water flows and storages as parts of the universal water cycle. Because there is no substitute for water (like, for example, substitutes for fossil fuels), societies will continue demanding water in great amounts. Therefore, water management and treatment technologies will continue being top priority, and innovation in this area will play a key role in sustainability.
While there are many hot topics to review in this area (we did it to some extent and you should feel free to explore more background on your own), our main focus in this lesson is to learn how to evaluate prospective technologies based on the available information. This may be not a simple exercise, but rather a quite complex practical task. That is why it is important to tap into real-world studies and learn from them. Activities in this lesson give you some scenarios to work with and will hopefully provide you with some practice of evaluatory thinking.
Type | Assignment Directions | Submit To |
---|---|---|
Reading | Complete all necessary reading assigned in this lesson. Do not forget to open the links in the text. Although many linked materials are considered supplemental (unless it is marked as "reading assignment"), you will benefit from including those materials in your learning - they give you a more complete story on the topic and contain great examples. | |
Forum Discussion |
Use this online calculator [13] to determine the waste water generation rate at your household. You will need to check all question marks on the house model to supply specific information. In the end, go to "Show results", where you get statistics for your water use. Then take a look at your annual water bill (if available) - how does your actual water use compare to the number output by the calculator? (Calculator uses averaged data and assumptions for appliances but does not take into account individual conservation measures, so the results may differ) If you take your water use as an average (per household) in your area, can you estimate the total domestic wastewater generation in your hometown or area? How does that compare to the capacity of your local wastewater treatment facility? You may need to check your municipality websites for information such as capacity and the area they serve. |
Share your results in the Lesson 6 Discussion Forum. |
Activity | Watch these two videos comparing biological and chemical methods of water treatment. Chemical vs. Biological Wastewater Treatment - Part 1 [33] Chemical vs. Biological Wastewater Treatment - Part 2 [34] In a brief (2 page max) report, express your opinion on the three questions: (1) Which type of water treatment seems to be preferable – indicate specific advantages; (2) What holds off the universal application of this preferable technology - indicate specific disadvantages or obstacles; (3) If you are asked to issue a recommendation on which type of treatment to use at your location, what key questions would you investigate as part of your decision-making? Feel free to search more information on the methods discussed in the videos and those used at your local area treatment plants. Submission deadline: Wednesday (before midnight) - check Canvas calendar for specific dates. |
Upload assignment in docx or pdf format to Lesson 6 Activity Dropbox. |
Course Project | Revisit Lesson 12, which provides guidance on the Course Project. Unless you have already started, this is the time to work on the technical review for your course project. This interim report should summarize important operational data on your technology of choice. It should cover the operation principles, status of the technology, technical promise, readiness for implementation (TRL), areas of impact, technical obstacles (e.g., efficiency, design flaws, etc.), and examples of application (if any). Later, this report will serve as a resource for you to articulate technical information for your final project proposal. Please make sure to include proper citations for the information and images you use. Submission deadline: check Canvas calendar for specific dates. |
Bonton, A., Bouchard, C., Barbeau, B., Jedrzejak, Comparative life cycle assessment of water treatment plants, Desalination 283, 42-54 (2012).
CSR, Rules of Department of Natural Resources, Chapter 7: Water Quality, Code of State Regulations, 2014.
Dhinadhayalan, M., Nema, A., Decentralised wastewater management - New concepts and innovative technological feasibility for developing countries, Sustain. Environ. Res., 22(1), 39-44 (2012).
Girard, J.E., Principle of Environmental Chemistry, 3rd Ed., Jones & Bartlett Learning (2013).
US EPA Water Conservation Plan Guidelines, Appendix A: Water Conservation Measures, pp. 143-155, EPA (1998).
USDA, Conservation and the Water Cycle [8], Natural Resources Conservation Service, 2001.
USGS, Estimated Use of Water in the United States in 2005, [35] Circular 1344, 2009.
Vorosmarty, C.J., Sahagian, D., Anthropogenic Disturbance of the Terrestrial Water Cycle, BioScience, vol. 50, pp.753-763 (2000).
Links
[1] https://www.epa.gov/watersense/water-conservation-plan-guidelines
[2] https://www.epa.gov/sites/production/files/2017-03/documents/appendix-a-water-conservation-measures.pdf
[3] https://www.sfwmd.gov/our-work/kissimmee-river
[4] http://www.flickr.com/photos/jaxstrong/8455826149/sizes/l/
[5] https://www.nsf.gov/
[6] https://www.youtube.com/embed/al-do-HGuIk
[7] https://www.usgs.gov/special-topics/water-science-school/science/water-cycle-diagrams
[8] http://www.wcc.nrcs.usda.gov/factpub/aib326.html
[9] https://www.e-education.psu.edu/eme807/sites/www.e-education.psu.edu.eme807/files/files/cycle_scheme_4m.pdf
[10] https://pubs.usgs.gov/circ/1441/circ1441.pdf
[11] https://www.usgs.gov/
[12] http://commons.wikimedia.org/wiki/File:SiphonTubes.JPG
[13] http://www.csgnetwork.com/waterusagecalc.html
[14] https://watercalculator.org/
[15] http://www.theguardian.com/sustainable-business/new-water-technologies-save-planet
[16] https://www.flickr.com/search/?text=Heike%20Hoffmann
[17] http://www.flickr.com/photos/gtzecosan/5546714555/sizes/l/
[18] https://www.youtube.com/c/thecityofwinnipeg
[19] https://www.youtube.com/embed/PNN0OuI54JM
[20] https://www.youtube.com/user/theregionofpeel
[21] https://www.youtube.com/embed/vC42YTIjxpM
[22] http://water.epa.gov/scitech/wastetech/mtbfact.cfm
[23] https://www.sos.mo.gov/cmsimages/adrules/csr/previous/10csr/10csr0708/10c20-7a.pdf
[24] https://www.flickr.com/search/?q=ed%20bolton
[25] http://www.flickr.com/photos/ebolton/3894800090/sizes/l/
[26] http://www.ecovillagefindhorn.com/findhornecovillage/biological.php
[27] http://www.toddecological.com/
[28] https://www.ted.com/speakers/michael_pritchard
[29] https://embed-ssl.ted.com/talks/michael_pritchard_invents_a_water_filter.html
[30] http://inhabitat.com/6-water-purifying-devices-for-clean-drinking-water-in-the-developing-world/
[31] http://www.sciencedirect.com/science/article/pii/S0011916411007375
[32] https://iwaponline.com/ws/article-abstract/9/4/439/26529/Life-cycle-assessment-of-three-water-supply?redirectedFrom=fulltext
[33] http://www.youtube.com/watch?v=-VjmFaxQwMo
[34] https://www.youtube.com/watch?v=N9BrWTD20co
[35] http://pubs.usgs.gov/circ/1344/pdf/c1344.pdf