tag:theconversation.com,2011:/us/topics/water-purification-7104/articlesWater purification – The Conversation2016-03-29T15:01:14Ztag:theconversation.com,2011:article/568772016-03-29T15:01:14Z2016-03-29T15:01:14ZWhat can fish mouths teach us about engineering clog-free filters?<figure><img src="https://images.theconversation.com/files/116536/original/image-20160328-17844-f3fapm.jpg?ixlib=rb-1.1.0&rect=1046%2C404%2C3241%2C2516&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Filter-feeding fish have had 150 million years to improve filtration.</span> <span class="attribution"><a class="source" href="https://www.flickr.com/photos/usfwsmtnprairie/9546645557/">Rob Holm / USFWS</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Filter-feeding fish accomplish a feat that human technologies cannot: species including goldfish, menhaden and basking sharks filter tiny algal cells or shrimp-like prey from huge volumes of water without clogging their oral filters.</p>
<p>Since fish have been filtering particles for more than 150 million years longer than human beings, we suspected fish may have evolved filter designs that use unknown processes to remain unclogged. So we decided to investigate.</p>
<p>Our research, <a href="http://nature.com/articles/doi:10.1038/ncomms11092">recently published in <em>Nature Communications</em></a>, combines approaches from biomechanics, medicine and ecology to explore how these fish retain and transport prey inside their mouths. Our goal is to provide ideas and data that could improve aquaculture, conservation and industrial filtration.</p>
<h2>Crossflow filtration works for fish and industry</h2>
<p>Until 15 years ago, we thought that most filter-feeding fish used oral structures called gill rakers in the same way that we use coffee filters or spaghetti strainers. These so-called dead-end sieves force water to pass straight through the pores of the mesh. But dead-end sieves always clog as particles accumulate over time to cover the filter surface.</p>
<p>The water flows right through a colander and leaves the spaghetti trapped on the mesh, but a fish needs to move the food from the gill raker filter to the back of its mouth for swallowing. Dead-end sieves would cause problems for fish, since their gill rakers would clog and fish don’t have a tongue to move food particles off the gill rakers. So we knew they must be using some other filtering technique.</p>
<p>By putting a biomedical endoscope inside the mouths of feeding fish, <a href="http://doi.org/10.1038/35086574">colleagues and I discovered in 2001</a> that several common fish species use crossflow filtration instead of trapping particles directly on a dead-end sieve.</p>
<p>During crossflow filtration, small secondary streams of fluid pass through each filter pore – perpendicular to the filter surface, like in dead-end filtration. But the main stream of fluid – the “crossflow” – is directed to travel across (parallel to) the filter surface, lifting particles off the filter and preventing the pores from clogging with particles.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=170&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=170&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=170&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=213&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=213&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116557/original/image-20160329-17835-zbfkb9.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=213&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A tilapia illustrating the current model of crossflow filtration, from Sanderson et al., doi: 10.1038/ncomms11092. The mainstream flow (MF) enters from the right and passes across the gill rakers (GR) that are attached to the branchial arches (BA). The mainstream flow carries concentrated particles to the back of the mouth for swallowing. The smaller secondary flows (the filtrate, Fi) pass through the pores of the gill raker filter.</span>
<span class="attribution"><span class="source">Virginia Greene, virginiagreeneillustration.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<p>Through the endoscope, we could see that the main flow of water heading toward the back of the mouth was transporting concentrated particles parallel to the gill raker filter. Less forceful streams of particle-free water exited between the gill rakers. All of these fluid dynamics are caused by the interaction of the water with the physical structures in the fish’s mouth.</p>
<p>We hadn’t expected to see crossflow filtration in fish, though this mechanism had been independently developed by industry a few decades earlier. Crossflow filtration avoids clogging and is often used to filter wastewater, pharmaceuticals, dairy foods and beverages such as beer and fruit juices.</p>
<p>Unfortunately, even <a href="https://en.wikipedia.org/wiki/Membrane_fouling">industrial crossflow filters still clog eventually</a>. Over time, as water exits through the filter pores, it deposits some particles on the filter. The filters must then be backflushed or cleaned with chemicals, causing a major operating expense.</p>
<p>So we turned again to fish, to see whether millions of years of evolution might have come up with unique crossflow filter designs.</p>
<h2>Biomimetic designs from fish mouths</h2>
<p>We started our study by examining basic structures inside fish mouths, familiar to fishermen and aquarium hobbyists. Fish gill rakers – the “feeding filters” – are attached to the branchial arches. These arches are bone or cartilage “ribs” inside the mouth that also support the bright red gills for gas exchange. The arches are typically positioned one after another from the front of the mouth back toward the esophagus, where food is swallowed. Scientists hadn’t previously considered the effects these branchial arches could have on patterns of water flow.</p>
<p>For our latest research, we made our own filters by using computer-aided design (CAD) software and 3D printing to create cone-shaped plastic models of fish mouths. We covered the branchial arch “ribs” with a fine nylon mesh.</p>
<p>We based our physical models on paddlefish and basking sharks because their branchial arches form a series of tall ribs that are separated by deep grooves. In our models, each rib served as a <a href="https://www.youtube.com/watch?v=JP94PR9vE7g">backward-facing step</a> that interacted with the crossflow of water traveling over the step.</p>
<p>Almost anywhere that water flows over a backward-facing step, a vortex is created automatically. For this reason, the closely-spaced tall ribs (“<em>d</em>-type ribs”) in these fish mouths aren’t often used by engineers because of the disruptive vortices that form continuously in the grooves between the ribs.</p>
<p>We designed many models with different versions of these backward-facing steps to test the effects of varying characteristics like height and distance between the steps. Interestingly, designs for some microfluidics devices that are used in labs for cell sorting have similar rib-like structures.</p>
<p>Both paddlefish and basking sharks are ram filter feeders that <a href="https://www.youtube.com/watch?v=7Y5c9l4Eev8">swim forward with a completely open mouth to capture prey</a>. To simulate this kind of feeding, my three undergraduate student coauthors, Erin Roberts, Jillian Lineburg and Hannah Brooks, and I conducted experiments in a flow tank. We submerged our stationary models in a constant stream of water inside the tank. The models “fed” on particles as we adjusted the speed of the water in the flow tank and added particles of different sizes, shapes and densities to the water.</p>
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<a href="https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=183&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=183&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=183&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=231&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=231&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116558/original/image-20160329-17859-bmyuik.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=231&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A paddlefish illustrating the new vortical cross-step filtration model, from Sanderson et al., doi: 10.1038/ncomms11092. The mainstream flow (MF) enters from the right and interacts with the series of backward-facing steps that are formed by the branchial arches (BA), causing vortical flow (Vo). The vortex interacts with the gill rakers (GR) to concentrate particles for transport towards the back of the mouth to be swallowed.</span>
<span class="attribution"><span class="source">Virginia Greene, virginiagreeneillustration.com</span>, <a class="license" href="http://creativecommons.org/licenses/by-nc-nd/4.0/">CC BY-NC-ND</a></span>
</figcaption>
</figure>
<h2>Unique vortical cross-step filtration in fish</h2>
<p>Like the spinning of a mini-tornado, water passed over the backward-facing steps inside our models and formed a distinct vortex in the groove between each pair of ribs. We designed accessory structures to control the movement of the vortices by creating regions of the model where the flow couldn’t escape easily. High shear rates around the vortices scoured particles off the mesh, preventing clogging.</p>
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<a href="https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/116532/original/image-20160328-17862-1jfs3q7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Green dye helps visualize the vortices generated in model paddlefish and basking shark mouths.</span>
<span class="attribution"><span class="source">S. Laurie Sanderson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>We manipulated the vortices to carry particles to the floor of the models, showing that fish could be using this highly adaptable filtration system like a “hydrodynamic tongue” to move particles inside their mouths.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/l03n9gVbkrc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">We manipulated the vortices in our models to transport concentrated particles along the vortex axis, downstream from each backward-facing step. The vortices lifted particles from the mesh and carried them toward the floor of the model.</span></figcaption>
</figure>
<p>Small preserved paddlefish from an aquaculture company, placed in the flow tank in filter-feeding position, also formed vortices that concentrated particles inside the mouth. This suggests that we’ve correctly identified and modeled structures that are important for generating vortices inside real fish mouths.</p>
<p>This new filtration method, which we term “vortical cross-step filtration,” is effective even when the mesh is damaged or missing from a large portion of the models. Just like fish can continue to feed even when their gill rakers are still growing or are torn, our models can capture particles even when there are large holes in the mesh.</p>
<p>Although we’d identified vortices as a potential mechanism for fish filtration as early as 2001, data on particle capture by vortical flow in fish mouths haven’t been published previously.</p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/1T7MXCxbatM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Rhodamine dye traces the path of a vortex that forms downstream from a backward-facing step. The step mimics a branchial arch inside a fish’s mouth.</span></figcaption>
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<h2>The future of cross-step filtration</h2>
<p>Our biomimetic models of paddlefish and basking shark mouths use novel arrangements of engineering structures that harness vortical flow to retain and transport tiny food particles. Cross-step filtration could also apply to filter-feeding ducks, baleen whales and the gill rakers of filter-feeding fish such as <a href="http://www.sciencefriday.com/videos/no-strain-no-gain-filter-feeding-mantas-2/">manta rays</a>.</p>
<p>Understanding these vortices in fish opens new research directions for engineering improved filters with less clogging, as well as the rapid separation of cells for biomedical tests.</p><img src="https://counter.theconversation.com/content/56877/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>S.Laurie Sanderson is the inventor on U.S. and international patent applications filed by the College of William & Mary (provisional filing 02/2014; nonprovisional filing 02/2015; 14/619,377; PCT/US15/15419). This research on filter-feeding fish was funded in part by the National Science Foundation (NSF Grant IBN-0131293 to S.L.S.).</span></em></p>Even the best engineered filters get clogged eventually. Fish mouths have evolved structures that create unique fluid dynamics patterns that solve that problem.S. Laurie Sanderson, Professor of Biology, William & MaryLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/416972015-05-15T04:33:06Z2015-05-15T04:33:06ZWhy Africans must join forces to protect scarce water resources<figure><img src="https://images.theconversation.com/files/81536/original/image-20150513-2468-10erqrm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Unless water is governed properly, the African continent will face massive problems in the coming years.</span> <span class="attribution"><span class="source">EPA/JIM HOLLANDER</span></span></figcaption></figure><p>African water resources are under increasing stress and the continent is likely to face significant water <a href="http://www.un.org/waterforlifedecade/scarcity.shtml">shortages by 2030</a>. Population growth combined with climate change and continued economic development will put further stresses on water resources and infrastructure. </p>
<p>Effectively and equitably governing Africa’s water resources is vitally important. One of the most effective solutions will be for industry, civil society and all levels of government to join forces.</p>
<p>It is impossible to downplay the importance of water for human individuals, societies, and the natural environment. We depend on it for food, energy and for the natural functioning of ecosystems.</p>
<p>Ignoring the problem or praying for rain will not solve Africa’s water insecurity. There is a much harder task ahead - building resilient communities that acknowledge water’s political nature while working together to govern it.</p>
<h2>A bleak outlook</h2>
<p>The overall security of global freshwater resources is bleak. Places as diverse as <a href="http://www.theguardian.com/world/2015/jan/17/sao-paulos-water-supply-in-critical-condition-as-drought-bites">São Paulo</a>, <a href="http://www.nytimes.com/2015/04/02/us/california-imposes-first-ever-water-restrictions-to-deal-with-drought.html&assetType=nyt_now">California</a>, <a href="http://www.thezimmail.co.zw/2015/03/04/zvishavane-poised-for-another-drought/">Zimbabwe</a>, and <a href="http://www.latimes.com/world/asia/la-fg-taiwan-drought-20150510-story.html">Taiwan</a> have all recently experienced drought conditions, severely disrupting living conditions.</p>
<p>Globally, there is a growing chasm between availability and supply, our awareness of water’s preciousness and our ability to govern it. Add in the upheaval from changing weather patterns due to climate change and the complexity deepens.</p>
<p>Unless things change, by 2030 the world will face a 40% [shortfall](<a href="http://unesdoc.unesco.org/images/0023/002318/231823E.pdf">2015 World Water Development Report.</a> between availibility and demand. This is because trends around climate change and economic development in the least developed and emerging economies are converging. The authors of a [recent UN report](<a href="http://unesdoc.unesco.org/images/0023/002318/231823E.pdf">2015 World Water Development Report.</a> on water write: </p>
<blockquote>
<p>This convergence is certain to intensify the water insecurity of poor and marginalised people in low-income countries and add to the urgency for new approaches to the allocation of water resources for development.</p>
</blockquote>
<p>For Africa, already struggling with water insecurity, these deeply vexing challenges will only intensify over time.</p>
<p>Sub-Saharan Africa’s population is expected to <a href="http://www.prb.org/Publications/Datasheets/2013/2013-world-population-data-sheet.aspx">increase to 2.4 billion by 2050</a>. Africa’s <a href="http://www.theguardian.com/global-development/2014/jul/10/urban-population-growth-africa-asia-united-nations">urban population is expected to double</a> by 2030 and the movement towards cities will also exacerbate water stress.</p>
<p>Already the number of people who can rely on piped water to their premises has <a href="http://www.unicef.org/gambia/Progress_on_drinking_water_and_sanitation_2014_update.pdf">decreased from 42% to 34%</a>. Safe drinking water in urban areas will continue to be a major problem in cities across the continent. </p>
<h2>Unpacking the politics of water</h2>
<p>Water problems are political problems and require political solutions. Increasingly, scholars from a range of disciplines are <a href="http://www.sciencedirect.com/science/article/pii/S0264837712001020">focusing on governance</a> as a <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4959.2009.00344.x/abstract">key variable</a> in the quest for increased water security. Governance requires a toolbox of rules, procedures, norms, and a recognition of particular power dynamics. There is also a focus on how alliances will overcome complex problems that need integration and coordination. </p>
<p>Water clearly intersects with a range of social and environmental issues that, at first glance, bear no connection. Working together can plug the gaping holes in governance that emerge from top-down management. It also reflects our growing networked society, where a decision in one sector can have a knock-on effect in intended and unintended ways.</p>
<p>Most crucially collaborative water governance can overcome the gaps that come from weakened or illegitimate centralised political authorities. </p>
<h2>Bargaining, negotiation and compromise</h2>
<p>Because water is infused with politics it can lead to deep divisions between competing communities. Equally, it can generate the necessary will to cooperate. Several approaches grounded in local contexts but built on a common spirit of <a href="http://www.tandfonline.com/doi/abs/10.1080/11926422.2013.846269">hydrosolidarity</a> need to be pursued.</p>
<p>It is crucial that NGOs, traditional communities and business interests are all included in partnerships with various levels of government to ensure water is managed effectively. </p>
<p>Including a diversity of stakeholders <a href="http://www.sciencedirect.com/science/article/pii/S0016718513001838">in the political process</a> has a number of positive effects. Technical knowledge of local water resources is spread, effective resolution of conflicts are found, legitimacy is increased, and costs are cut. </p>
<p>Regional cooperation is also absolutely essential given that there are <a href="http://unesdoc.unesco.org/images/0023/002318/231823E.pdf">more than 80 international rivers and aquifers</a> across the continent. </p>
<p>It is also necessary to learn from and improve existing examples of collaborative water governance, including South Africa’s <a href="http://www.durban.gov.za/City_Services/development_planning_management/environmental_planning_climate_protection/Projects/Pages/Investment-in-Ecosystem-Services.aspx">uMngeni Ecological Infrastructure Partnership</a>, and the Swiss-funded <a href="http://iucn.org/about/work/programmes/water/wp_our_work/wp_our_work_bridge/">Bridge Program</a> which is active across the continent. </p>
<p>We must understand that the seeds for sustainable water security are often sown through the dirty work of bargaining, negotiation, and compromise.</p>
<h2>No silver bullet</h2>
<p>Given Africa’s water insecurity, it may be surprising to learn that <a href="http://unesdoc.unesco.org/images/0023/002318/231823E.pdf">only 5% </a>of the continent’s potential water resources are developed. There is clearly plenty of opportunity for growth. The challenge will be to sustainably manage that growth.</p>
<p>There is no miraculous technological innovation that will guarantee water security and no package of funding from multilateral donors or national coffers that will fully alleviate water shortages.</p>
<p>Water security involves a number of interrelated pieces: the population, food, energy, land, sanitation, infrastructure, social development, international relations and environmental integrity. A focus on building collaborative governance is a necessary step to increasing water security.</p><img src="https://counter.theconversation.com/content/41697/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Harrington receives funding from the National Research Foundation of South Africa. Any opinion, findings and conclusions or recommendations expressed in this material are those of the author and therefore the NRF does not accept any liability in regard thereto.</span></em></p>Managing Africa’s water sources is a matter of vital importance for people to have any hope of surviving on the continentCameron Harrington, Postdoctoral Fellow , University of Cape TownLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/297352014-08-11T13:32:52Z2014-08-11T13:32:52ZIt’s public attitudes to recycled sewage that need better treatment, not the water<figure><img src="https://images.theconversation.com/files/55033/original/6nd7xcnd-1406544822.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Whose round? Mine's a pint.</span> <span class="attribution"><a class="source" href="http://commons.wikimedia.org/wiki/File:Discharge_pipe.jpg">USDA</a></span></figcaption></figure><p>The amount of water at the Earth’s surface is pretty constant, but in many parts of the developed world we are running out of the right sort of water, and our ability to access it. The severe water shortages experienced in <a href="http://www.desertsun.com/story/news/investigations/2014/08/10/california-record-heat-extreme-drought/13856149/">California</a> and the <a href="http://www.telegraph.co.uk/news/worldnews/northamerica/usa/10989695/Western-US-water-crisis-worse-than-thought.html">southwestern US</a>, in Australia, and even <a href="http://www.metoffice.gov.uk/climate/uk/interesting/2012-drought">parts of the UK</a> show we need new methods for ensuring a clean water supply.</p>
<p>One is to produce high quality water from wastewater, something that is improving all the time. While this could help relieve the strain on water supplies, public attitudes to the idea of using water that is recycled from sewage and other wastewater streams for drinking and domestic use is the more significant barrier.</p>
<p>The treatment and reuse of “grey” water (waste from baths, showers, washing machines and so on) for non-drinking uses such as irrigation is <a href="http://www.epa.gov/region9/water/recycling/">already widespread</a>. But as the demand for water grows and supplies continue to dwindle, more and more attention is being paid to “black” water – in simple terms, sewage. </p>
<p>Technological advances and <a href="http://www.wfduk.org/about-uktag">environmental regulations</a> have made the production of very high quality water from black wastewater streams not just <a href="http://www.acs.org/content/dam/acsorg/education/resources/highschool/chemmatters/recycled-sewage.pdf">feasible</a>, but increasingly an economic and political necessity. The challenge facing water engineers now is arguably just as significant: convincing the public to accept sewage water recycled in this way for mainstream domestic consumption.</p>
<h2>Public attitudes as hard as the water</h2>
<p>Let’s be clear. Untreated sewage is dangerous stuff, responsible throughout history (and all-too-often still today <a href="http://www.wateraid.org/uk/what-we-do/the-crisis">for many communities worldwide</a>) for more deaths, disease and misery than pretty much any other single cause. </p>
<p>Industrial wastewater treatment is rightly considered one of the wonders of the modern world. Customers of modern water utilities companies expect reliable, high-quality water supply and removal as a given, to the extent that the majority <a href="http://www.southernwater.co.uk/pdf/about-us/publications/wrmp/SOR/A04_Wastewater-Recycling.pdf">have no idea</a> where their water comes from, or goes to.</p>
<p>In practice, of course, wastewater discharged into the environment from one community has long become the source water for another community downstream – think Oxford, to Reading, to London in a chain along the river Thames. Urban myths about the number of people who have already tasted a Londoner’s tap water are deeply ingrained and somehow accepted. But when asked directly about the acceptability of recycled wastewater as a direct feed into potable supplies, attitudes harden.</p>
<p>In an Oregon State University survey in 2008, while a majority supported a specific water recycling proposal in principle, the percentage of people strongly agreeing with potential applications <a href="http://oregonstate.edu/cla/mpp/sites/default/files/pdf/waterwater_survey_results.pdf">dropped to as low as 13%</a> for uses associated with human contact or consumption, from around 55% for other industrial and municipal uses. </p>
<p>In a 2013 poll for The Guardian newspaper, 63% of respondents claimed <a href="http://www.theguardian.com/environment/shortcuts/poll/2013/may/10/water-health">they would drink recycled sewage water</a>, but the context was broader and the question more hypothetical than in the Oregon study. </p>
<p>This psychological factor is <a href="http://www.apa.org/monitor/sep04/toilet.aspx">important</a>: like the fly in your soup, we are put off when a problem is placed close at hand. The key is to add steps in the process – discharging treated wastewater to the river before abstracting it again for drinking.</p>
<p>A 2012 Southern Water study suggests this approach would be acceptable, if the quality <a href="http://www.southernwater.co.uk/pdf/about-us/publications/wrmp/SOR/A04_Wastewater-Recycling.pdf">could be guaranteed</a>. Recent evidence on the prevalence of <a href="http://www.sciencedirect.com/science/article/pii/S0048969713000429">antibiotic-resistant microbes in treatment plants</a> highlights the need for ongoing technical development to combat emerging threats to health and environment. Other concerns lie around persistent organic pollutants such as pharmaceuticals, which <a href="http://www.theguardian.com/environment/shortcuts/poll/2013/may/10/water-health">may be concentrated</a> by repeated recycling of black wastewater.</p>
<p>In striving to introduce recycled water systems, water engineers face the challenge of tackling real and perceived threats to water quality, mistrust of commercial utilities and government authorities, and a deep-rooted fear of contaminated water.</p>
<p>Ironically, climate change could be part of the answer. Wichita Falls, Texas, became in July 2014 the first place in the world to implement 50:50 mixing of <a href="http://www.star-telegram.com/2014/07/11/5965036/in-drought-stricken-wichita-falls.html?rh=1">directly recycled wastewater in domestic supplies</a>. Residents are largely philosophical about their “potty water”, but then they’re experiencing the <a href="http://www.cbsnews.com/news/toilet-to-tap-wastewater-recycling-begins-in-wichita-falls-texas/">worst drought in 70 years</a> with extreme restrictions on water use. In Wichita Falls, it’s state politicians and regulators rather than consumers that are the largest hurdles the scheme must jump.</p>
<h2>Solutions from experience</h2>
<p>Water resource managers occupy a shifting landscape between technological capability, political precaution, and public attitudes which can swing strongly and quickly. Navigating this difficult terrain while introducing engineering answers that work is complex, but the evidence suggests that trust is key to public acceptance. </p>
<p>In California, Israel, Australia and Singapore, environmental concerns, price incentives, fines and even national security have been used to convince people of the need to adopt wastewater recycling. <a href="http://www.water.org.uk/home/news/press-releases/wastewater-pamphlet/wastewater-web--2-.pdf">Information campaigns</a>, celebrity endorsements, aggressive branding and collaboration with trusted independent organisations are designed to reduce the yuck factor. </p>
<p>In the final analysis however, necessity and urgency are the most effective levers of opinion, as Wichita Falls appears to prove. Perhaps the real challenge for water engineers is to find a way to secure the infrastructure for resilient, sustainable water supplies almost behind the scenes, ready to press the button when circumstances drive public and politicians to accept the unacceptable.</p><img src="https://counter.theconversation.com/content/29735/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jonathan Bridge has received funding from the Natural Environment Research Council and the Technology Strategy Board for work related to human health risks from waterborne pathogens.</span></em></p>The amount of water at the Earth’s surface is pretty constant, but in many parts of the developed world we are running out of the right sort of water, and our ability to access it. The severe water shortages…Jonathan Bridge, Lecturer in Environmental Engineering, University of LiverpoolLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/202022013-11-19T02:58:39Z2013-11-19T02:58:39ZSolving the toilet shortage needs a bottom-up approach<figure><img src="https://images.theconversation.com/files/35068/original/tbbcb7yf-1384305962.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">What toilet? In this refugee camp, children play in the holes dug for latrines. </span> <span class="attribution"><span class="source">Oxfam International</span></span></figcaption></figure><p>Why does <a href="https://www.un.org/waterforlifedecade/sanitation.shtml">one third</a> of the world’s population have inadequate sanitation?</p>
<p>Hopefully I can shed a bit of light on this. You see, my work is shit – literally – which is why I call myself a water, sanitation and hygiene (<a href="http://www.unicef.org/wash/">WASH</a>) engineer.</p>
<p>When people aren’t completely scared off by my choice of discussion topics – such as faeces or the even more taboo <a href="http://www.tandfonline.com/doi/abs/10.1080/13552071003600083">menstrual hygiene management</a> – they do often ask me why such a large proportion of the global population is still without adequate sanitation.</p>
<p>We, “the experts”, have already spent billions of dollars on this. So why haven’t we succeeded in giving more people in developing countries access to <a href="http://www.worldtoiletday.org/learn_detail.php?id=1">toilets</a>?</p>
<p>Well, we have tried: in the 1960s and 1970s, international aid was all about providing infrastructure. Here’s a water treatment plant. Here’s a toilet. Now go for your life.</p>
<p>But these often failed to consider the social, cultural, environmental and economic suitability and sustainability of different WASH interventions.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/35124/original/4r53h8hm-1384317485.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/35124/original/4r53h8hm-1384317485.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/35124/original/4r53h8hm-1384317485.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/35124/original/4r53h8hm-1384317485.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/35124/original/4r53h8hm-1384317485.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/35124/original/4r53h8hm-1384317485.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/35124/original/4r53h8hm-1384317485.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/35124/original/4r53h8hm-1384317485.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A newly completed latrine in Kenya.</span>
<span class="attribution"><span class="source">computerwhiz417</span></span>
</figcaption>
</figure>
<p>If you are used to relieving yourself in nature, why would you listen to these “experts” telling you that it is “healthier” to lock yourself in a small, foul-smelling box, even if it was given to you for free?</p>
<p>If you are an <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3156.2011.02927.x/full">adolescent girl</a> who has just started menstruating, is it useful for you to have a school toilet which provides no bins or washing facilities, and has to be shared with adolescent boys? Probably not.</p>
<h2>What’s ‘appropriate’?</h2>
<p>This is not to say that there aren’t amazing things going on in WASH nowadays, thanks to programs led by NGOs, governments, universities, industry and, probably most importantly, communities themselves.</p>
<p>But it is not as simple as “giving” people a toilet, or a tap, or tampons. A lot of the people to whom I speak assume that being a WASH engineer, I (and my colleagues) must have all the answers. We do not.</p>
<p>In most developing communities, the most appropriate technology is often quite modest and to be honest, in many cases the local users have much better skills than engineers at transforming WASH technologies to suit their own situations. Even the best university-taught skills aren’t going to be particularly useful there.</p>
<h2>Do I still have a job then?</h2>
<p>Yes. WASH practitioners and researchers are now working on how they can ensure that WASH facilities, services and behaviours are sustainable and relevant in local contexts.</p>
<p>Giving someone access to a toilet or water source at some fixed point in time, which is how the UN <a href="http://www.wssinfo.org/">currently measures</a> the <a href="http://www.un.org/millenniumgoals/">Millennium Development Goals</a> for water and sanitation, does not imply that this will achieve “sustainable access”.</p>
<p>If the users do not value the benefits, they will not use the facilities. If the users do not have the capacity or the resources to maintain and repair the systems, they will fall into disuse.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/35064/original/8t4gg4vj-1384303999.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/35064/original/8t4gg4vj-1384303999.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/35064/original/8t4gg4vj-1384303999.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/35064/original/8t4gg4vj-1384303999.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/35064/original/8t4gg4vj-1384303999.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/35064/original/8t4gg4vj-1384303999.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=501&fit=crop&dpr=1 754w, https://images.theconversation.com/files/35064/original/8t4gg4vj-1384303999.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=501&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/35064/original/8t4gg4vj-1384303999.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=501&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The wash basins at this school are set at different heights for use by girls of different ages.</span>
<span class="attribution"><span class="source">Overseas Development Institute</span></span>
</figcaption>
</figure>
<p>The development literature is riddled with examples. And even if a community does obtain “sustainable access” to WASH facilities and services, do they really want them? Has access to these enhanced their health, self-worth, freedom and, ultimately, well-being?</p>
<p>Nobel Laureate <a href="http://scholar.harvard.edu/sen">Amartya Sen</a> would certainly argue that development cannot be achieved without these. His seminal book <a href="http://www.nytimes.com/books/first/s/sen-development.html">Development as Freedom</a> argues that without sufficient capabilities being attained and freedoms being met (including good health, stable finances, political freedom and access to opportunities) a person has not yet attained the well-being required to be considered “developed”.</p>
<p><a href="http://www.participatorymethods.org/">Participatory research methods</a> have highlighted that outside “experts” cannot walk into communities sprouting preconceived ideas of development: community members are the experts on their own lives. </p>
<p>The emphasis has shifted to building trust and rapport with these communities and giving them the support to develop workable solutions to address their immediate concerns.</p>
<p>This is where we can participate – by working alongside these communities and sharing our knowledge, be that in engineering, marketing, behaviour change or a myriad of other fields.</p>
<p>Communities bring their intimate knowledge of their own situations. It is through <a href="http://www.iwaponline.com/washdev/up/washdev2013166.htm">collaboration</a> that we can help communities to improve their WASH facilities, services and behaviours, and develop their capacities, which, in turn, enhance their well-being.</p>
<p>It is no longer acceptable to simply assume that we know best – and, in my experience, the communities that I’ve worked with are not scared off when I start talking to them about toilet behaviours.</p>
<p>They tell me that their children are often <a href="http://bmjopen.bmj.com/content/3/8/e003476.abstract">sick with diarrhoea</a> and they think that their WASH situation has something to do with it.</p>
<p>It is <a href="http://rsh.sagepub.com/content/132/5/240">too important</a> an issue to be labelled taboo.</p>
<p><br></p>
<p><strong>See also:</strong><br>
<a href="https://theconversation.com/video-solving-the-worlds-toilet-shortage-25738">VIDEO: Solving the world’s toilet shortage</a></p><img src="https://counter.theconversation.com/content/20202/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Dani Barrington is employed by Monash University as a Research Fellow. Her current work is funded as part of the AusAID Australian Development Research Awards Scheme. She is also affiliated with Engineers Without Borders, where she is Editor of the Journal of Humanitarian Engineering.</span></em></p>Why does one third of the world’s population have inadequate sanitation? Hopefully I can shed a bit of light on this. You see, my work is shit – literally – which is why I call myself a water, sanitation…Dani Barrington, Research Fellow in Water, Sanitation and Hygiene, Monash UniversityLicensed as Creative Commons – attribution, no derivatives.