Why did a Canadian town’s water supply turn pink?

Pink water. Image: Magic Momentz/Flickr/creative commons.

Most of us take it for granted that the taps in our homes will deliver safe and clean water for drinking, cooking, showering and cleaning. This means there is usually little interest from the public in how the water gets there. However, it took less than a day for a story from Onoway, a small town in Alberta, Canada, with just over 1,000 residents, to make it from social media to global newsfeeds. “Bright pink water comes out of taps in Canada!” – suddenly we are all interested in water treatment methods. The Conversation

To enjoy the benefits of clear and safe water, a hidden but valuable infrastructure of water treatment exists in our cities and villages. These are operated and maintained by engineers and scientists, and among them are water chemists. These chemists have been investigating the use of neat chemical reactions to remove undesired chemicals and potential pathogens from naturally sourced water and to prepare the water for its safe journey through distribution systems.

The local drinking water treatment plant of Onoway treats its water using potassium permanganate. This is an almost black looking solid which forms a bright purple solution in water and also removes dissolved iron and another metal called manganese.

Iron and manganese are not harmful to human health, but if these metals are present at high concentrations it can lead to deposits in the water distribution system and discolouration of the water. However, the auburn tints of iron seem boring compared to the spectacular pink that has raised global interest and lively social media discussions.

Customers are very sensitive to the colour, taste and odour of drinking water – these are the human senses used to assess water quality – so this incident has understandably caused alarm. The pink colour stems from some potassium permanganate that escaped through a failed valve and into the drinking water distribution system, eventually ending up with the customers.

Potassium permanganate has been used in drinking water treatment for more than 100 years. In addition to iron and manganese removal, it is used to remove taste and odour as well as to control undesired algal or mussel growth in treatment works. It also has disinfecting properties. Permanganate forms solid, black manganese dioxide when it reacts with the water contaminants – and this can then be filtered out of the water.


A little goes a long way

Potassium permanganate has the chemical structure KMnO4 and is a compound that is electron deficient – that is, it doesn’t have enough electrons. This lack of electrons makes it a strong oxidant that readily reacts with a wide range of unwanted compounds in water. It belongs to an established group of water treatment chemicals that can be summarised under the term “conventional chemical oxidants”, which also include oxygen, chlorine, chlorine dioxide, ozone, hydrogen peroxide and, in the wider sense, UV light.

Water is typically treated with a dose of 1-3mg of potassium permanganate per litre of water, which is quite a small amount. But only unreacted potassium permanganate has a visible pink colour in water and is visible even at very low concentrations – as low as 0.05 mg per litre of water – so it doesn’t take much to add colour.

Since only small quantities of permanganate can change the colour of water, customer complaints relating to residual permanganate are known to occur . This means treatment works usually take care to remove any unreacted, coloured permanganate before the water reaches consumers.

The pink water does not pose a threat to human health but skin irritation related to potassium permanganate is known at a certain concentration. Onoway’s mayor claimed that customers were not at risk. However, these concentrations seemed to vary – some had water merely tinted pink whereas some water was bright purple. Regardless of what shade of pink they receive, customers are advised to rely on alternative drinking water sources until the permanganate is flushed out of the distribution system.

Water treatment isn’t simple

For water treatment, there is no one-size fits all approach. Drinking water treatment processes vary due to different local water resources and what the traditional and established technologies are. Iron and manganese can be removed by alternative methods, such as aeration, which uses the oxygen present in the air, or by running the water over catalytic granules consisting of manganese dioxide. But every method has its specific advantages and disadvantages.

Many parameters need to be evaluated before making an informed decision on which method to use to treat a water supply – but there’s no doubt that potassium permanganate is one of the more colourful methods.

Jannis Wenk is a lecturer in water science and engineering at the University of Bath.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Which pairs of capital cities are the closest together?

Vienna, which is quite close to Bratislava, but not quite close enough. Image: Thomas Ledl

It doesn't take long to get from Paris to Brussels. An hour and a half on a comfortable Thalys train will get you there. 

Which raises an intriguing question, if you like that sort of thing: wich capital cities of neighbouring countries are the closest together? And which are the furthest away? 

There are some that one might think would be quite close, which are actually much further part. 

Buenos Aires, Argentina's capital, sits on one side of the estuary of the Río de la Plata, while Montevideo, Uruguay's capital lies on the other side. 

Click to expand: Image: Google Maps

But at 207km apart, they're not really that close at all. 

Similarly, Singapore – capital of, er, Singapore – always sticks in the mind as 'that bit on the end of the Malaysian sticky-out bit'. But it's actually pretty far away from Kuala Lumpur, Malaysia's capital. A whole 319km away, in fact:

Click to expand: Image: Google Maps

Thinking of 'countries that cause problems by being close together', you inevitably think of South Korea and North Korea. 

Click to expand: Image: Google Maps

And while Pyongyang in the North and Seoul in the South are pretty close together, 181km just isn't going to cut it. 

Time to do some Seoul-searching to find the real answer here.

(Sorry.)

(Okay, not that sorry.)

Another place where countries being close together tends to cause problems is the Middle East. Damascus, the capital of Syria, really isn't that far from Beirut, in Lebanon. Just 76km:

Click to expand: Image: Google Maps

Seeing as Lebanon is currently host to millions of refugees fleeing the horrors of Syria's never-ending civil war and the atrocities of Daesh, or Isis, this is presumably something that authorities in Beirut have given a certain amount of thought to.

Most of the time, finding nearby capitals is a game of searching out which bits of the world have lots of small countries, and then rooting around. So you'd think Central America would be ripe for close-together capital fun. 

And yet the best option is Guatemala and El Salvador – where the imaginatively named Guatemala City is a whole 179km away from the also imaginatively named San Salvador.  

Click to expand: Image: Google Maps

Another obvious place with lots of small-ish countries is Europe – the site of the pair of capitals that drove me to write this nonsense in the first place. 

Click to expand: Image: Google Maps

And in fairness, Vienna and Bratislava do make a pretty good showing of it. Austria's capital sits on the Danube; drift downstream, and you swiftly get to Slovakia's capital. As the crow flies, it's 56km – though as the man swims, it's a little longer. 

There are more surprising entries – particularly if you're willing to bend the rules a little bit. Bahrain and Qatar aren't really adjacent in the traditional sense, as they have no land border, but let's just go with it. 

Click to expand: Image: Google Maps

Manama, Bahrain's capital, is 140km away from Doha, the centre of the world's thriving local connecting-flight-industry which moonlights as Qatar's capital. 

Sticking with the maritime theme, Port of Spain in Trinidad and Tobago is 152km from St George's, Grenada. 

Click to expand: Image: Google Maps

Good, but not good enough. 

Castries, the capital of the Carribbean country of St Lucia, is 102km north of Kingstown, the capital of St Vincent and the Grenadines. 

Click to expand: Image: Google Maps

Better, but still not good enough. 

Basseterre, the capital of St Kitts and Nevis, inches ahead at 100km away from St John's, the capital of Antigua and Barbuda.

Click to expand: Image: Google Maps

But, enough teasing: it's time to get down to the big beasts.

If you ask Google Maps to tell you the distance between the capital of Congo and the Democratic Republic of the Congo, it comes up with a rather suspect 20km. 

 

Click to expand: Image: Google Maps

A short distance, but considering the only thing separating the two is the River Congo, something's up: Google places the centre of Brazzaville a little north of where it should be, and the centre of Kinshasa many many miles south of where it should be, in some sort of suburb.


So, in true CityMetric style, we turn to train stations. 

Though such transport hubs may not always perfectly mark the centre of a city – just ask London Oxford Airport or London Paddington – in this case it seems about right. 

Kinshasa's main train station is helpfully called 'Gare Centrale', and is almost slap-bang in the middle of the area Google marks as 'Centre Ville'. On the other side of the river, 'Gare de Brazzaville' is in the middle of lots of densely-packed buildings, and is right next to a Basilica, which is always a good sign. 

 

Click to expand: Image: Google Maps

And when marking that distance, you get a more realistic 4.8km. If you want to be really keen, the ferry between them travels 3.99km, and the closest point I could find between actual buildings was 1.74km, though admittedly that's in a more suburban area. 

Pretty close, though. 

But! I can hear the inevitable cries clamouring for an end to this. So, time to give the people what they want. 

Click to expand: Image: Google Maps

If you ask Google Maps to tell you how far away the Holy See, capital of the Vatican, is from Rome, capital of Rome, it says 3.5km. 

Click to expand: Image: Google Maps

If you set the centre of Rome to be the Palatine Hill, the ancient marking point for roads leading out of Rome, that narrows to 2.6km.

 

Click to expand: Image: Google Maps

Fiddle a bit and put the centre of the Vatican as, well, the middle bit of the roughly-circular Vatican, that opens up a smidge to 2.75km.

Click to expand: Image: Google Maps

Mark the centre of point of the Vatican as the approximate location of St Peter's Tomb within St Peter's Basilica, which is after all the main reason the Vatican is a thing and not just a quirky suburb of Rome, and 2.67km is your answer. 

Though obviously in practice Rome and the Vatican are as far away as one single step over the railings at the entrance of St Peter's Square, which fairly blatantly makes them the closest capital cities in the world. 

But that would have been a very boring thing to come out and say at the start. 

Oh, and if you hadn't worked it out already, the longest distance between a capital city and the capital of a country it shares a land border with is 6,395km. 

Click to expand: Image: Google Maps

I know it's tough for you, Vladimir and Kim. Long-distance relationships are a real struggle sometimes.

I can't make a pun work on either Moscow or Pyongyang here, but readers' submissions more than welcome. 

Jack May is a regular contributor to CityMetric and tweets as @JackO_May.

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