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.

 
 
 
 

What other British cities can learn from the Tyne & Wear Metro

A Metro train at Monument. Image: Callum Cape/Wikipedia.

Ask any person on the street what they know about Newcastle, and they’ll list a few things. They’ll mention the accent; they’ll mention the football; they’ll mention brown ale and Sting and Greggs. They might even mention coal or shipbuilding, and then the conversation will inevitably turn political, and you’ll wish you hadn’t stopped to ask someone about Newcastle at all.

They won’t, however, mention the Tyne and Wear Metro, because they haven’t probably heard of it – which is a shame, because the Metro is one of the best things the north-east has to offer.

Two main issues plague suburban trains. One is frequency. Suburban rail networks often run on poor frequency; to take Birmingham for an example, most of its trains operate at 30-minute intervals.

The other is simplicity. Using Birmingham again, the entire system is built around New Street, leading to a very simple network. Actually, that’s not quite true: if you’re coming from Leamington Spa, Warwick, Stourbridge, Solihull or a host of other major minor (minor major?) towns, you don’t actually connect to New Street – no, you don’t even connect to the ENTIRE SYSTEM BUILT AROUND NEW STREET except at Smethwick Galton Bridge, miles away in the western suburbs, where the physical tracks don’t even connect – they pass over each other. Plus, what on earth is the blue line to Walsall doing?

An ageing map of the West Midlands rail network: click any of the images in this article to expand them. Image: Transport for the West Midlands/Centro.

But Newcastle has long been a hub of railway activity. Tragically, the north-east has fewer active railway lines than any other region of the UK. Less tragically, this is because Tyne and Wear has the Metro.


The Metro was formed in 1980 from a somewhat eccentric collection of railways, including freight-only lines, part of the old Tyneside Electrics route, underground tunnelling through the city centre, track-sharing on the National Rail route to Sunderland, and lines closed after the Beeching axe fell in the early 1960s.

From this random group of railway lines, the Metro has managed to produce a very simple network of two lines. Both take a somewhat circuitous route, the Yellow line especially, because it’s literally a circle for much of its route; but they get to most of the major population centres. And frequency is excellent – a basic 5 trains an hour, with 10 tph on the inner core, increasing at peak times (my local station sees 17 tph each way in the morning peak).

Fares are simple, too: there are only three zones, and they’re generally good value, whilst the Metro has been a national leader in pay-as-you-go technology (PAYG), with a tap-in, tap-out system. The Metro also shares many characteristics of European light rail systems – for example, it uses the metric system (although this will doubtless revert to miles and chains post-Brexit, whilst fares will be paid in shillings).

 

The Metro network. Image: Nexus.

Perhaps most importantly, the Metro has been the British pioneer for the Karlsruhe model, in which light rail trains share tracks with mainline services. This began in 2002 with the extension to Sunderland, and, with new bi-mode trains coming in the next ten years, the Metro could expand further around the northeast. The Sheffield Supertram also recently adopted this model with its expansion to Rotherham; other cities, like Manchester, are considering similar moves.

However, these cities aren’t considering what the Metro has done best – amalgamated local lines to allow people to get around a city easily. Most cities’ rail services are focused on those commuters who travel in from outside, instead of allowing travel within a city; there’s no coherent system of corridors allowing residents to travel within the limits of a city.

The Metro doesn’t only offer lessons to big cities. Oxford, for example, currently has dire public transport, focused on busy buses which share the same congested roads as private vehicles; the city currently has only two rail stations near the centre (red dots).

Image: Google.

But it doesn’t need to be this way. For a start, Oxford is a fairly lateral city, featuring lots of north-south movements, along broadly the same route the railway line follows. So, using some existing infrastructure and reinstating other parts, Oxford’s public transport could be drastically improved. With limited engineering work, new stations could be built on the current track (blue dots on the map below; with more extensive work, the Cowley branch could be reinstated, too (orange dots). Electrify this new six-station route and, hey presto, Oxford has a functioning metro system; the short length of the route also means that few trains would be necessary for a fequent service.

Image: Google.

Next up: Leeds. West Yorkshire is a densely populated area with a large number of railway lines. Perfect! I hear you cry. Imperfect! I cry in return. Waaaaaah! Cry the people of Leeds, who, after two cancelled rapid transit schemes, have had enough of imaginative public transport projects.

Here’s a map of West Yorkshire:

Image: Google.

Here’s a map of West Yorkshire’s railway network:

 ​

Image: West Yorkshire Metro.

The problem is that all of the lines go to major towns, places like Dewsbury, Halifax or Castleford, which need a mainline connection due to their size. Options for a metro service are limited.

But that’s not to say they’re non-existent. For example, the Leeds-Bradford Interchange line passes through densely populated areas; and anyway, Bradford Interchange is a terminus, so it’s poorly suited to service as a through station, as it’s currently being used.

Image: Google.

With several extra stops, this line could be converted to a higher frequency light rail operation. It would then enter an underground section just before Holbeck; trains from Halifax could now reach Leeds via the Dewsbury line. The underground section would pass underneath Leeds station, therefore freeing up capacity at the mainline station, potentially simplifying the track layout as well.

 

Image: Google.

Then you have the lines from Dewsbury and Wakefield, which nearly touch here:

Image: Google.

By building a chord, services from Morley northwards could run into Leeds via the Wakefield line, leaving the Dewsbury line north of Morley open for light rail operation, probably with an interchange at the aforementioned station.

Image: Google.

The Leeds-Micklefield section of the Leeds-York line could also be put into metro service, by building a chord west of Woodlesford over the River Aire and connecting at Neville Hill Depot (this would involve running services from York and Selby via Castleford instead):

The path of the proposed chord, in white. Image: Google.

With a section of underground track in Leeds city centre, and an underground line into the north-east of Leeds – an area completely unserved by rail transport at present – the overall map could look like this, with the pink and yellow dots representing different lines:

Et voila! Image: Google.

Leeds would then have a light-rail based public transport system, with potential for expansion using the Karlsruhe model. It wouldn’t even be too expensive, as it mainly uses existing infrastructure. (Okay, the northeastern tunnel would be pricey, but would deliver huge benefits for the area.)

Why aren’t more cities doing this? Local council leaders often talk about introducing “metro-style services” – but they avoid committing to real metro projects because they’re more expensive than piecemeal improvements to the local rail system, and they’re often more complex to deliver (with the lack of space in modern-day city centres, real metro systems need tunnels).

But metro systems can provide huge benefits to cities, with more stops, a joined-up network, and simpler fares. More cities should follow the example of the Tyne and Wear Metro.