Drinking water from the floods
Researcher in ground-breaking project
As much as 1.3 million cubic metres of storm water collected in Malta's reservoirs and dams may start being turned into high quality potable water thanks to ground-breaking research by a local water treatment engineer.
While Malta obtains most of its fresh water through sea water reverse osmosis plants - the largest single consumers of electricity in the country - storm water flowing on the streets and in valleys is channelled to the sea as fast as possible to prevent flooding.
But thanks to an idea developed by Marco Cremona of Sustech Consulting, rainwater flowing in valleys and pouring into reservoirs from the streets can be treated to produce potable water for as much as 35,000 people each year, at a third of the electricity needed by reverse osmosis plants.
Once purified, the water can be immediately pumped into the water mains.
With his German partners at Herco Wassertechnik GmbH of Freiberg, Mr Cremona designed and built a water treatment plant using state-of-the-art ultra filtration membranes.
He installed the test plant at Torri Cumbo, limits of Ta' Qali in January 2005 after reaching an agreement with the Water Services Corporation. The device was set off to treat run-off water from Chadwick Lakes and obtained "very satisfactory" results. The plant produces 3,000 litres of potable water per hour.
"Samples taken both from the untreated and the filtered water were tested at the WSC laboratory with very positive results," Mr Cremona said, explaining that storm water is essentially very good quality potable water with a miniscule amount of impurities suspended in it.
"The amount of dissolved matter in the water is negligible: the water is not salty, not hard and contains only small amount of nitrates. Chemically, it is comparable to bottled water. So what is required is an efficient system to remove silt and any microbiology, as well as traces of pesticides and organics, which may be present in the water. We believe that our process will do exactly this," Mr Cremona said.
Being of a better quality than groundwater and desalinated seawater, purified storm water can be produced at a more competitive cost: "The water pressure required to treat storm water is a fraction of what is needed for reverse osmosis. Besides, more than 90 per cent of potable water is recovered from a single unit of storm water. The ratio of purified water yielded when salt is extracted from sea water is just 40 per cent at best."
The treatment process will entail the emptying of the storm water reservoirs and the pumping of the purified water into the water mains, substituting water from the reverse osmosis plants or groundwater, while increasing the effective water-holding capacity of the storm water reservoirs. In this way, flooding is also being mitigated," Mr Cremona said.
Converting storm water to potable water is a completely novel idea. A thorough worldwide search for similar studies and tests, in fact, only came up with the treatment of storm water to prevent pollution of water bodies in Pittsburgh, United States, which was focused on pollution prevention and not on using the treated water as a source of potable water.
The project will go into its second phase as the first showers start falling in September by when Mr Cremona would have installed a patented electro-precipitation plant for testing in unison with the ultra filtration unit, in a bid to further improve the efficiency of the system and the quality of the water.
The pre-treatment plant will be supplied free of charge by Fraunhofer Technologie-Entwicklungsgruppe of Germany, the largest organisation for applied research in Europe which has also allocated a PhD student to focus solely on the development of the project. Tests are expected to go on till May next year.
The water engineer has had discussions with the Department of Public Health (the regulator on water quality) and the Malta Resources Authority (the regulator on water supply) on the viability of treating storm water, explaining that these regulatory authorities have been very supportive of his initiative.
"I also presented the project to Investments Minister Austin Gatt last February. He expressed a particular interest in the project, especially the commercialisation of the idea on a national scale," Mr Cremona said.
The potential of upscaling the pilot project looks very promising. "It is the declared intention of the Ministry for Resources and Infrastructure to construct underground tunnels in flood-prone areas using EU Structural Funds. This provides an excellent and timely opportunity for a field-tested and reliable treatment process able to turn this water into potable water," he said.
The project is also a seed project of the EuroMEDITI initiative of the Malta Council for Science and Technology (MCST), aimed at developing Malta into an outstanding technology and innovation platform in the Euro-Mediterranean region.