More energy realities

The Water Services Corporation would like to clarify some inaccuracies in E.A. Mallia's letter entitled 'Some more energy realities' (The Sunday Times, August 3).

The Gozo polishing plant works on the same principle as reverse osmosis and removes excess chlorides (salts) and other impurities from water that is extracted from underground sources. The resultant extra pure water is then blended with groundwater in reservoirs to produce drinking water that meets EU and local standards.

Prof. Mallia stated that the energy consumption of the Gozo Polishing Plant is a secret. Although the figure was not published in our annual report, this does not mean there is any secrecy. The current consumption is 1.38 kW/h per m3.

The figure of 50 per cent of input water rejected is for seawater desalination. Only 30 per cent of extracted groundwater in Gozo is polished and, of this, only 20 per cent of input water is rejected. This means that only around six per cent of groundwater is rejected.

Prof. Mallia wrote that the Ċirkewwa pipeline is also used - which only places more demand on power stations. Gozo's water supply is more or less independent from that of Malta, but is supplemented (around 18 per cent annually) by an undersea pipeline from the Cirkewwa reverse osmosis plant in times of very heavy demand in summer or during maintenance.

However, the water from Cirkewwa is produced by a state-of-the-art facility whose electricity consumption is extremely low after a recent upgrade co-financed by EU funds. These upgrades have brought about a 43 per cent reduction in electricity in this plant alone. The corporation uses such a practice so as not to increase the stress on the groundwater during the summer season.

I would like to debunk the commonly held myth that reverse osmosis plants in Malta consume around 20 per cent of the nation's electricity. The truth is that due to aggressive upgrading programmes and the intelligent introduction of energy-saving and monitoring regimes, the Water Services Corporation has reduced its electricity consumption (in real terms) to around four per cent of Malta's total consumption. Put in another way, producing a cubic metre of pure drinking water from sea water now costs around a third of what it used to.

Prof. Mallia said that we have no plans to use treated wastewater. This is also incorrect. The wastewater treatment plant in Gozo is treating 4,560 m³/day and the standard reached so far is one that complies with the Urban Waste Water Directive. The corporation is constantly monitoring the effluent produced to develop the right product for irrigation. The chloride level in the treated effluent is currently 840 mg/l. The corporation intends to step up its controls on illegal discharges into the sewers so that further improvements in effluent waters may be obtained.