Water Industry News
scientists fear Mediterranean pollution from Palestinian
By Prof. Steve Brenner
More problems lie ahead due to the evacuation from Gaza, and this one is due to the evacuation - of human waste.
Professor Steve Brenner, an oceanographer who has studied the circulation of the eastern Mediterranean Sea, warns that lack of careful planning of sewage disposal in Gaza will cause severe ecological problems for Israel.
Currently the domestic sewage is slowly absorbed into the ground. With an increase in population this could change to having it dumped into the sea. Israel has strict measures to prevent this, but since there is now nothing to stop the Palestinians, they could resort to this method. If using the sea for disposal is not designed properly, this could do harm along the coast of Ashkelon since this flows in a northerly direction. If this problem is not given serious thought, very serious problems will arise.
In many parts of the world, including developed countries, sewage from large cities along the coast is disposed of at sea by either dumping the sludge far offshore (usually tens of kilometers) or by discharging the treated wastewater into the sea through an outfall located beyond the breaker zone. In the former case, the assumption is that the sludge will remain cohesive and sink to the bottom in deep water where the environmental impacts will be minimal. In the latter case, it is assumed that the ocean currents will mix and dilute the wastewater with seawater and spread the pollutants over a large area, thereby reducing the concentrations to environmentally acceptable levels. It is important to locate the outfall beyond the breaker zone (typically several kilometers) in order to avoid problems of the pollutants washing up on the immediate shore. By the generic term "pollutants" we refer to dissolved and suspended inorganic and organic material as well as to various bacteria. The latter generally pose the greatest immediate health risk, and high concentrations usually lead to the closing of bathing beaches.
The current situation in Gaza City, with more than one million residents, is to discharge the domestic sewage into a holding pool north of the city where the wastewater slowly percolates into the ground. As the population of the Gaza Strip grows, it is clear that an alternative disposal system will have to be established and it is most likely that the choice will be discharge into the sea. Until the present, this has not occurred due to the environmental controls and restrictions enforced by the State of Israel. Upon the Israeli withdrawal from this region, nothing will prevent the Palestinians from switching to the very simple and attractive option of ocean disposal. If this is not properly planned, assessed, and monitored, the dire consequences for Israel will be the equivalent of an ecological time bomb.
Based on direct current measurements that were conduced over a period of several years off the coast of Ashkelon and Ashdod, as well as extensive studies of the circulation in the southeastern Mediterranean Sea based on simulations and forecasts with a state-of-the-art ocean circulation model, it has been shown conclusively that throughout the year the predominant direction of flow in this region is along the coast, directed from south to north. The cross-shore component of flow is weaker and fluctuates between onshore and offshore depending upon the depth, the precise current direction, and the wind speed and direction. There is little doubt that any effluents discharged into the sea off the coast of Gaza will spread northward into the territorial waters and the coastal zone of Israel.
The potential concentrations and dilution of these effluents as well and the potential environmental impacts cannot be quantitatively assessed without conducting a proper environmental impact study. Nevertheless, we can draw some preliminary qualitative conclusions based on the experience of the Gush Dan sewage outfall, which services the greater Tel Aviv area. This outfall is located 4.5-5 km offshore where the water depth is 38 m. The zone around the outfall has been extensively studied and monitored by scientists from Israel Oceanographic and Limnological Research (IOLR) for many years. Their long-term results clearly show that the seabed and sediments are affected by the effluents at distances of as much as 5 km to the north and 1 km to the south (due to the mainly northward currents). It should be noted that this is for the case of treated effluents. Perhaps a better indication of the potentially dire environmental consequences of an unplanned and unmonitored outfall can be seen in the accident that occurred in February 2003 when the pipeline ruptured and partially untreated wastewater was discharged directly into the sea over a period of several weeks. Satellite images of the sea surface as well as numerical simulations of the circulation at this time clearly showed the north to northeastward spread of the plume, which came ashore and affected the entire coastline of Tel Aviv and the area to the north. The bathing beaches in this area were closed by the Ministry of Health and the Ministry of the Environment for an extended period due to the deterioration of the water quality.
Based on this preliminary assessment, there is little doubt that an improperly designed sewage outfall from Gaza will adversely affect the coast of Ashkelon within a very short period of a few weeks or less. Since the outfall would presumably operate continuously, the detrimental effects in Ashkelon will grow with time while the longer term environmental impacts may very well be felt in Ashdod and even further north.