Re-assessing the Extent of Impact of Malta’s (Central Mediterranean) Major Sewage Outfall Using ERS SAR

ERS SAR (Synthetic Aperture Radar) imagery has been used to re-assess the geographical extent of coastal area, which is exposed to environmental impact from Malta’s main sewage outfall at Wied Ghammieq. The outfall presently discharges almost 80% of all the wastewater produced on the island, untreated into the sea. This is carried out through a 716 m long submarine outfall equipped with a terminal diffuser. A number of past short-term field surveys had indicated that the geographical extent of the impacted area may extend up to 8 km south-east of the outfall, especially when the submarine outfall is malfunctioning. SAR imagery, reviewed in the present study, indicates that the geographical extent of the impacted coastline may be in fact three times longer than originally estimated. Support for this suggestion is presented through a review of bathing water quality of areas upstream and downstream to the present outfall.