Local marine wastewater discharges : characterisation and impacts

Abstract

Raw municipal wastewaters from the three major sewage pumping stations in the Maltese Islands were sampled three times daily over a 7-day period in August-September 2002 so as to identify levels of suspended matter, nutrients (nitrates, nitrites, orthophosphates and total phosphorus), and biodegradable organic matter (measured indirectly as BOD5), as well as temporal and spatial variations in such levels. BOD5 levels of raw municipal wastewaters sampled at regular intervals over a 24-hour period in February 2003 from Wied il-Pwales pumping station, and of selected industrial wastewaters, were also investigated. Superficial marine sediments from the vicinity of the two major sewage outfall sites in the Maltese Islands, and from selected reference sites, were also sampled in November 2005 so as to identify level of heavy metals (namely cadmium, copper, lead and zinc), and relate these to the loads of the same metals being released by the discharge of wastewaters.