Underwater pipeline could solve ecological havoc from Delimara
James Debono The construction of a pipeline that channels warm water from the power station’s cooling system into deeper waters could save the Hofra z-Zghira cover in Marsaxlokk from the ecological havoc wreaked by the new power station extension.
This is what AIS Consultants, the authors of an additional assessment of the extension requested by MEPA, conclude.
Sea water is currently pumped into the Delimara power station’s cooling system from an inlet at the power station quay in Marsaxlokk harbour, and exits on the other side of the Delimara peninsula directly into il-Hofra iz-Zghira.
This cover presently receives 29,500m3 of cooling water every hour, which is 8ºC above the average water temperature in the area. With the proposed power station extension, the amount of warmer water will increase to 43,000m3 every hour.
The cooling water is treated by a biocide agent, in order to maintain the operational efficiency of the plant. The proposed 144MW extension would require an additional 450 litres a week of sulphuric acid and 450 litres per week of Biocaf (a brand of biocide) which will end into the sea.
The discharge from this increased flow of warm water and biocides is expected to have a negative impact on sea grasses and corals. Increased sea temperature is expected to result in reduced oxygen in the water, which could affect fish physiology, including spawning, egg hatching and development, feeding, digestion and growth.
“Overall marine biodiversity is expected to further decrease since most marine species are not particularly heat-tolerant,” the report concludes.
The report explores three solutions to address this problem. One possible solution used abroad is to dispose the water into an artificial cooling pond. But this solution is excluded because a power plant like Delimara would require a pond with a cooling surface of around 3.6 km2 which equates to around 75% of Marsaxlokk, including the Delimara Peninsula.
Another solution could be building a cooling tower to reduce the temperature of the water to ambient water temperature before discharge. But this has a significant negative visual impact, and takes up land space earmarked for future expansion of the power station. It would give rise to an increase in the noise levels in the area.
The construction of an outfall pipeline would also cause a disturbance to the marine environment, so the report suggests underwater tunnelling. But impacts at the point of discharge may still lead to environmental degradation.
The best solution according to the report is to combine a mechanical draft cooling tower with an extended outfall. Such a combination could result in a smaller cooling tower and a shorter outfall with a reduced water flow.
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