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5.14 Desalination

In many parts of the world, surface water or non-saline groundwater stocks are not adequate to satisfy the water demand. While one may immediately think of the Middle East as being one such area, it is less obvious that many islands (e.g. the Canary Isles, Madeira, the Channel Islands) also suffer the same problem. In such circumstances, people have been forced to consider the sea and brackish underground aquifers as water sources. To make these saline waters potable, the salt has first to be
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5.9 Membrane filtration

Membrane filtration is a process whereby particles smaller than about 10−2 mm (which can pass through sand filters) are removed using synthetic polymeric membranes and a high pressure. The membrane effectively acts as a sieve.

It is increasingly becoming popular as an advanced treatment process for water (especially for removal of Cryptosporidium) and wastewater (where water reuse takes place), and various possibilities are:


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5.7.1 Mixed oxidant gases system

This is a relatively new system of disinfection. It involves electrolysis of high-purity NaCl brine to produce a mixture of chlorine dioxide, ozone and hypochlorite. This mixture is separated within the electrochemical cell by a membrane, or by exploiting density difference, and is then metered into the water requiring disinfection. The mixed oxidant gases are generated on demand and this is a great safety advantage, compared with having storage tanks of chlorine on site. The source for the d
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3.4 Chemical characteristics of natural waters

Since water is such a good solvent, it is not surprising to find many different chemical substances present in it. Water, on reaching a river, will contain inorganic and organic compounds which were dissolved as rainwater percolated through the soil and rocks. In addition, some gases will dissolve in rainwater during its passage through the air.

The substances present in water may be conveniently grouped into:

  1. those from dissolved gases such as o
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2.4 Keyboard and mouse alternatives

Described image
Figure 11 An ergono
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Art in Renaissance Venice
This free course, Art in Renaissance Venice, considers the art of Renaissance Venice and how such art was determined in many ways by the city's geographical location and ethnically diverse population. Studying Venice and its art offers a challenge to the conventional notion of Renaissance art as an entirely Italian phenomenon. First published on Fri, 15 Jan
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Approaching poetry
Do you want to get more out of your reading of poetry? This free course, Approaching poetry, is designed to develop the analytical skills you need for a more in-depth study of literary texts. You will learn about rhythm, alliteration, rhyme, poetic inversion, voice and line lengths and endings. You will examine poems that do not rhyme and learn how to compare and contrast poetry. Author(s): Creator not set

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Introducing the philosophy of religion
In this free course, Introducing the philosophy of religion, Timothy Chappell, Professor of Philosophy, asks what the words 'God' and 'religion' mean, and what it means to ask philosophical questions about them. First published on Fri, 05 Feb 2016 as Author(s): Creator not set

History of reading tutorial 3: Famous writers and their reading - Elizabeth Barrett Browning and Ver
Have you ever wondered about the reading tastes and habits of famous writers in the past? This free course, History of reading tutorial 3: Famous writers and their reading Elizabeth Barrett Browning and Vernon Lee, is the third tutorial in a series designed to help users of the UK Reading Experience Database (UK RED) search, browse and use this resource, and explores the connections between the evidence of a writers reading and their literary output. The previous tutorials focus on methods of un
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Medicine transformed: on access to healthcare
Access to healthcare is important to all of us. Did the arrival of state medicine in the twentieth century mean that everyone had access to good medical services? If you fell sick in 1930 where could you get treatment from a GP, a hospital, a nurse? This free course, Medicine transformed: On access to healthcare, shows that in the early twentieth century, access to care was unequally divided. The rich could afford care; working men, women and children were helped by the state; others had to rely
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Brighton Pavilion
In this free course, Brighton Pavilion, you will examine the Royal Pavilion at Brighton, and its relationship to nineteenth-century Romanticism and exoticism. You'll begin with a biographical discussion of the Prince of Wales, afterwards Prince Regent and eventually King George IV, to whose specifications the Pavilion was built. With the help of video and still images you will take a tour of the Pavilion, examining the exterior then a series of interior rooms as a visitor in the 1820s may have e
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Getting started on classical Latin
This free course, Getting started on classical Latin, has been developed in response to requests from learners who had had no contact with Latin before and who felt they would like to spend a little time preparing for the kind of learning that studying a classical language involves. The course will give you a taster of what is involved in the very early stages of learning Latin and will offer you the opportunity to put in some early practice. Author(s): Creator not set

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Veiling
This free course explores controversies associated with the practice of 'veiling' within Islam. The Islamic 'veil', be it in the form of the hijab, niqab, jilbab or burqa (we shall explore this terminology in more detail later), has been at the centre of many different controversies. Many of these controversies can be understood in the context of debates about different citizenship models and different understandings of the roles, rights and demands of faith groups in society. In some instances,
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1.2 Round and flat characters

What about minor or peripheral characters? How deeply do they have to be imagined?

Activity 2

Click on ‘Round and flat characters’ below to read the next section. Showing the contradictions in characters is o
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Keep on learning

Study another free course

There are more than 800 courses on OpenLearn for you to
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5.4 Assessing Hume's views

The main value of Hume's essay lies in its discussion of our duties to God. Here Hume's arguments initially seem quite convincing. But arguments almost always seem convincing when they are first heard and understood. The real test comes when we try to think of possible objections. Here is one such objection, based on what has become known as the problem of evil, the problem of reconciling God's benevolence and omnipotence with the fact that evil exists in the world:

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6 The Thermidorian Settlement and the end of the Revolution

In Thermidor (July) 1794 there was a further political coup, this time engineered by deputies in the Convention who felt that Jacobin fanaticism, mob violence and bloodshed had got wildly out of hand and feared for their own lives. They succeeded in outmanoeuvring Robespierre, who was arrested and (after a botched suicide attempt) guillotined together with over 100 other Jacobins. The Thermidorians then put a stop to show trials and bloodletting. They also called in the army to put dow
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3.1 The moderate reformers

1789–92 was a period of relatively moderate reform in the spirit of the Enlightenment – moderate, that is, compared with what followed. It was certainly revolutionary in relation to what went before. The Constituent Assembly (August 1789–September 1791) and its successor, the Legislative Assembly (October 1791–August 1792), comprising educated members of the Third Estate joined by liberal-minded nobles and clergy, were satisfied with the transformation of absolute monarchy into
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1.4 The economics of maintaining a heritage site

The National Trust operates within a complex web of funding. This comes from annual membership fees and from visitor receipts at individual sites. Each National Trust property is responsible for raising the income necessary to fund its own conservation activities and further development (although a large minority of sites cannot cover their costs). Properties raise this income through visitors charges and from catering, shop sales, etc. Failure to raise sufficient income can lead to job losse
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1.2 Aberdulais Falls and the National Trust

When the National Trust took over the Aberdulais Falls and the associated buildings, the site was derelict, overgrown and dangerous. Prior to the Trust's ownership, public access to the Falls over the land surrounding it had been denied. Important decisions had to be taken regarding the future of the site.

The A465 slices through the site and the suburbs of Neath have encroached on the river bed on both sides.

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