Ireland has a tap water problem. In July and August 2018 various news outlets, including TheJournal.ie, The Irish Times and The Sun reported on an infringement case opened by the European Commission against Ireland.

Ireland had continuously failed to meet water safety standards agreed on 16 years ago. The European Commission took the case to the EU Court of Justice due to continuing high levels of trihalomethane (THM).

THM can form as a by-product when water is purified with chlorine. The chemicals within that group are linked to different types of cancers. According to the European Commission, Ireland was continuously exceeding THM levels in drinking water for about half a million people.

Water Pitcher
The chemicals inside tap water can be harmful to the human body and environment, new technology helps to make water safer.

But it is not only THM that causes problems with Irish tap water; chlorine itself poses another problem. Chlorine is a highly reactive chemical. It kills bacteria in water by destroying cell membranes. In small doses, the cells in human bodies can deal with chlorine. If the chlorine level rises, the water can irritate skin, eyes, and nose and cause gut problems.

Children and pregnant women are the groups with the highest risks when it comes to chlorine. This was shown by an incident that occurred last year in County Meath. Irish water issued a safety warning after children had developed rashes due to high chlorine levels in the water. People were advised to neither drink or otherwise consume the water nor use it to wash themselves. Both joe.ie and the Irish Times reported on the case.

But even normal chlorine levels, which are considered safe for human consumption can be fatal to the environment. Fish and other water-based wildlife can die from even small levels of chlorine.

Chlorination as a form of water purification is used in many countries in Europe and around the world. There are ongoing debates about the safety of the procedure with scientists arguing for both advantages and disadvantages.

So far it is not deemed unsafe to use chlorine for water purification. However, if you talk to people who have not grown up with chlorinated tap water, some concerns may arise.

“I used to buy bottled water when I first came to Ireland two years ago. But it got too expensive, so I switched to tap water. Ever since I had problems with my stomach.” says Deborah, a foreign student from Brazil.

Other students complain about dried out hair and skin or irritated eyes and noses.

And Yuwa, a student from Nigeria has trouble with acne: “I never had problems with acne, but since I came to Ireland my skin has been getting worse by the week”.

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So if chlorine in tap water can cause these effects in healthy adults, why is it still used?

There are two major water purification techniques used worldwide to purify drinking water. One method uses chlorine, the other uses ozone. Both are highly reactive.

Ozone needs more energy to produce and is highly corrosive so not all materials can be used in the purification process. This makes the ozone method the more expensive of the two.

Chlorine is cheaper to produce and remains in the water. This means that chlorine can continue to destroy bacteria even after the water leaves the purification plant. At first glance, this is an advantage over ozone, which eventually breaks up into oxygen.

The problem is, chlorine will also continue to react with other chemicals and form THM. On top of that, it does not differentiate between harmful bacteria and those who are actually good for us, like the ones living in the human digestive system.


Chlorine Pros and Cons

  • Cheap
  • Fast
  • Highly Effective
  • Kills bacteria after water leaves the purification plant

  • Taste
  • By-products linked to cancer
  • Chlorinated water linked to miscarriages and birth defects
  • Irritation of respiratory system, eyes and skin
  • Dangerous to water based flora and fauna

Ozone Pros and Cons

  • Tasteless and odour free
  • Close to no by-products
  • Highly effective
  • Dissolves into oxygen and leaves no chemical traces in water
  • Halts the accumulation of deposits in pipes

  • Complexity and high cost of production system and monitoring equipment
  • Corrosive, so it requires special materials in the purification plant
  • No residual effect, if bacteria survives it might remain in the water

Up until now, there has not been a real alternative to these two methods. But a development by scientist Dan Wang and his team of the Institute of Process Engineering at the Chinese Academy of Sciences in Beijing and Yangzhou University in Jiangsu aims to change that.

The scientists developed a 2-D sheet of graphitic carbon nitride. Graphitic carbon nitrite is a photocatalyst; it releases electrons when hit by sunlight. These electrons help to form chemicals to kill bacteria in the water. In tests, it killed 99.99 per cent of bacteria, including E.coli, in 10 litres of water in just 60 minutes. This is enough water to supply for the daily needs of a family of four to five people.

In a video excerpt, accompanying the publication of his article in Chem, Dan Wang highlights the importance of environmental friendly photocatalysts to battle water scarcity and energy shortage.

In this video, the scientists show how graphitic carbon nitride as a photocatalytic disinfectant purifies water.
Credit: Teng and Yang et al./Chem

Other photocatalysts exist but they are much less efficient or release dangerous by-products into the water during the chemical purification process. Graphitic carbon nitride forms hydrogen peroxide, which is often used in bleaching products. It dissolves into water after killing bacteria, so no dangerous by-products are formed during the process.

The scientists said that their main aim was to help provide clean water to underdeveloped regions, where purification plants are scarce. Their material cleans water, even if it is only left in a plastic bag in the sun.

On top of that graphitic carbon nitride is cheap to produce which can make it a good alternative to the ozone purification method.

Right now the scientists are unable to use their invention at a large scale. They now want to enlist the help of engineers to prepare their invention for commercial use.

In a world that is facing the early consequences of climate change a cheap and safe method to purify water is highly needed. Currently, about 900 million people do not have access to clean water.

And even for highly developed countries, this new method is promising.

In an interview with TheJournal.ie Gerard O’Leary, director of the EPA’s Office of Environmental Enforcement said Ireland will reach compliance with EU standards for clear water by the end of 2020. It will still use chlorine to purify water. But in the long run, Dan Wang’s invention has the potential to bring a safer method to the country and the world.