WSC makes energy savings despite higher production costs

Michael Falzon, chairman of the Water Services Corporation (WSC) said a system that recovers energy from waste water that was being pumped back into the sea from reverse osmosis (RO) plants had reduced electricity consumption by 10 per cent per cubic metre of water produced at the Pembroke plant.

This has been achieved while producing the same volume of potable water from the plant. But the savings have now been partly lost because of low rainfall over the past three years. This reduced supply from natural sources and necessitated higher production from RO plants.

Malta gets its water from three sources - RO plants, natural springs and water in the water table (aquifer) pumped from boreholes and from underground galleries.

Gozo is self-reliant on natural sources for most of the year except for water pumped from Malta during August because of the mass influx of non-Gozitans.

Up to two or three years ago water coming from RO plants, which desalinate seawater, represented half the potable water produced in Malta. Around 11 per cent still comes from boreholes.

Before the advent of the RO plants, the percentage of water from boreholes was much higher. Efforts were made and continue to be pursued to reduce extraction from the natural aquifer. This is because over-extraction over more than three decades has caused the saline content to increase.

Mr Falzon explained that energy-saving devices consisted of an adaptation of what is known in physics as a "Pelton wheel" to extract energy from water being jettisoned at high pressure back into the sea after the filtering process at RO plants.

In this manner, the water being pumped at high pressure back into the sea propels a wheel that in turn supplies more energy to an electricity-fired pump. This produces a 10 per cent saving in the electricity consumed by RO plants.

But because of lower rainfall in Malta particularly over the past three years, the three RO plants in Malta had to increase production because of lower supplies from natural springs. Thus after reaching a situation wherein RO plants supplied half of all Malta's needs, the rainfall shortage compelled WSC to increase water supply from RO plants.

The situation now is that RO plants are producing 60 per cent of Malta's water needs. The 10 per cent savings on corporation electricity bills and the contribution to lower emissions from the power stations, in addition to a lower import bill for oil, has thus been partially neutralised.

Mr Falzon pointed out that while many countries in the Mediterranean faced water shortages, the Maltese enjoyed a constant supply throughout the year, drought or no drought.

Addressing University students at a "Meet the Press" session last week, Mr Falzon also spoke on the measures being taken to improve the quality and taste of water supplied to Mosta, which has a population of over 18,000. Mosta residents get most of their water directly from Ta' Speranza pumping station and this water has a high salinity.

The corporation has taken steps so that water supplied to Mosta will be a blend of groundwater and water produced at RO plants that has no saline content. A pipeline linking Mosta to Naxxar reservoir will make this possible and work on this link is nearing completion.