Excessive nitrate levels in Malta’s aquifers have constrained the Water Services Corporation to increasingly rely on its more expensive reverse osmosis plants to supply adequate potable water to Maltese households and businesses.

The WSC has been extracting decreasing amounts of groundwater for distribution as tap water over the years. The reason, hydrologist Marco Cremona explained when contacted by this newspaper, is not primarily a question of quantity but rather of quality.

“A borehole in Malta’s important mean sea level aquifer will always provide water, but the salinity increases with over-pumping. However, I believe that the parameter of greatest concern to any potable water source is not salt but nitrate and this is what is forcing the WSC to progressively let go of its groundwater sources and increase its reliance on RO.”

The water the WSC distributes has to meet EU standards on potable water, which set a maximum nitrate level of 50 mg/l. This level is exceeded in 13 of Malta’s 15 aquifers including the most important mean sea level aquifers.

Excessive nitrate levels can cause numerous health problems, including a possible heightened cancer risk and gastric problems. But water that does not meet standards may include other contaminants, including microbes such as the Legionella bacterium which causes the potentially fatal Legionnaires’ disease, Mr Cremona explained.

To meet standards, the corporation mixes groundwater with nitrate-free water produced through reverse osmosis plants. But using the energy-intensive desalination plants is significantly more expensive than extracting groundwater.

The WSC may have a workaround for excessive nitrate levels, but bowser suppliers of fresh water, which also use groundwater, do not. Last year, the Environmental Health Directorate revoked eight licences for suppliers of first class water, as revealed by the EU Life+ Investing in Water Project headed by the Malta Business Bureau earlier this year. Just five suppliers remain.

Mr Cremona, who is the project’s water expert, said that lack of awareness may be leading households and businesses alike to obtain water from unlicensed suppliers, and which may not be fit for bathing and drinking. Over the past few weeks, the project has been carrying out water audits for businesses and hotels in a bid to reduce their water consumption, and these audits confirmed that bowser suppliers are heavily used.

“There are various bowser water suppliers who supply low quality groundwater and manage to sell it as potable, because people are completely unaware of the dangerous consequences of using low grade water – even for showers – and don’t even ask whether the water is certified by the public health authorities or not,” Mr Cremona said.

The Environmental Health Unit within the Public Health Department maintains a register of suppliers authorised to supply potable water, and Mr Cremona’s recommendation is for buyers to check this list, which also includes a number of hotels which set up their own small-scale reverse osmosis plants.

The main source of nitrates is agricultural activity, including the use of fertilisers. Mr Cremona noted that while farmers are meant to apply specific amounts, it is likely that they use more than they should, and the excess nitrates end up in Malta’s aquifers.

Other contributors to nitrates in groundwater include the storage of manure, and even leakage from the sewage system.

To address the issue, a Nitrates Action Programme which mostly regulates agricultural activity and which mandates fines and even imprisonment for offences, became law through a legal notice last year, and its provisions are starting to be implemented.

But it will be years, if not decades, before nitrate levels decrease – or even stop increasing – in aquifers, Mr Cremona noted, as it takes time for water to reach aquifers. Obviously, it is not physically possible to stop groundwater that is already infiltrating into the geology from reaching aquifers.

However, Mr Cremona adds, it is important to do what needs to be done, not just because of Malta’s obligations according to EU law but also, ultimately, because it is in Malta’s interest.