Nearly two-thirds of your tap water comes from the sea

The total amount of water produced from Reverse Osmosis plants has reached an all-time high of 22.8 million cubic metres, an average of 62,000 cb.m per day, the Water Services Corporation’s annual report reveals. 

While desalinated water now accounts for 64% of the complete water blend – up from 57% in 2017 – groundwater now accounts for 36%, down from 43% in 2017. 

The increase of RO water in the blend has contributed to a decrease in the salinity of tap water, because of its very blend of desalinated water and groundwater mixed in the corporation’s reservoirs. The higher the percentage of groundwater, the greater the need to treat it with chlorine to ensure it conforms to safety standards. 

Water salinity has been reduced by 17% during 2022, compared to the average levels recorded in 2021. The target for 2023 is to stabilise the salinity level at 2022 levels. The WSC intends to further reduce water salinity when the new tunnel connecting the Pembroke RO Plant to the Ta’ Qali group of reservoirs enters into operation. 

In 2022, the WSC produced a total of 35.5 million cb.m of potable water to meet water demand, an increase of 2.2 million cb.m in water production over five years ago. 

Peak summer production reached 71,000 cb.m per day in August, meaning production in this month is 13.5% higher than in 2021 both due to the increase in water demand and the need to improve the chloride level of the blend.  

Electricity bill stable, but set to increase by 7% 

Despite the increased reliance on the more energy-intensive RO process which consumes more electricity than groundwater pumps, the WSC electricity bill has decreased from €19.5 million in 2021 to €19.2 in 2022, largely thanks to increased efficiency.  

But the report now forecasts that the same bill will increase to €20.5 million which represents a 7% increase over 2022. 

The desalination unit within the WSC is currently upgrading the RO plants in Malta to increase the production capacity and improve energy efficiency, to ensure that desalinated water is produced at the minimum possible cost. 

About 52.9% of RO water in 2022 was produced from the Pembroke RO Plant, while the new plant in Ħondoq, Gozo, contributed 5% of the total desalinated water. Although the Ħondoq RO plant operated under ‘testing’ conditions for the first few months of 2022, it ran continuously from May 2022, giving the corporation the flexibility to transfer RO water to Malta. Previously, the submarine pipeline was only utilised to supply water from the Ċirkewwa RO plant to Gozo. 

The Ħondoq RO plant is also the most efficient plant, consuming 23.5% less energy than conventional plants, thus improving Malta’s desalination efficiency.  

Groundwater is currently abstracted from 68 boreholes and ten pumping stations in Malta, and 37 boreholes and two pumping stations in Gozo. 

To relieve pressures on the water table in heavily depleted zones, the WSC has reactivated eight boreholes which were not being used. 

Improving the taste of tap water 

The WSC is currently working with the University of Malta’s Food Sciences and Nutrition department in an EU-funded programme aimed at improving the taste of tap water by exploring alternatives to chlorination, which is presently the primary disinfection technology used for treating local potable water. 

While this ensures that tap water is completely safe for human health, it also contributes to its metallic taste thus discouraging the population from consuming it.  

The project has identified alternatives to chlorination. These included ultraviolet C (UVC) irradiation, a method using a specific wavelength of ultraviolet light to neutralise microorganisms. Other methods included hydrodynamic cavitation, a process involving a sudden decrease in pressure which triggers the formation of vapour and gas bubbles inside a liquid medium and electro-chlorination, a disinfection process achieved by passing an electric current through water.