Water. desalination + reuse

research section 3,000 Mollus Crus Poly no. specimens 2,500 2,000 1,500 1,000 500 8 VM 5S e VM pt0 1M 8 ay 09 VM 5M ay 09 VM 1S ep 09 VM 5S e VM p09 1M ay VM 10 5M ay 10 VM 1S ep 10 VM 5 Se p1 0 4 ep t0 1S VM VM 5S ep t0 4 4 VM 1S ep t0 ay 0 5M VM VM 1M ay 0 4 0 100% 90% 80% Mollus Crus Poly 70% 60% 50% 40% 30% 20% 10% 0 p1 10 ep VM 5 Se 10 1S VM 10 ay 5M VM 09 ay ep VM 1M 09 VM ep 1S VM 5S 09 09 ay 5M VM 1M VM ep 5S VM ay t0 8 8 t0 4 ep 1S VM 4 t0 ep t0 VM ep 1S VM 5S 04 ay 5M VM VM 1M ay 04 0% Figure 3. The number of specimens (upper panel) and the relative class distribution (lower panel) at Palmachim (2004, 2008-2010). Station VM1 located at the brine outfall; station VM5 , ** background. Samples were collected in 2004 prior to the SWRO plant operation. since the mixture disperses mainly at the surface, the dependence of chl-a on temperature and salinity should be checked on surficial samples only. The IEC data is being re-examined along these lines (A Glazer, personal communication) Seawater near the bottom at the Palmachim brine marine outfall was much more saline (up to 6 salinity units) and slightly warmer (around 0.5 ��C) than the surroundings. The effect was confined to the bottom 1 m and dispersed to more than 600 m from the outfall towards north-west, encompassing an area of ca 0.4 km2. Seawater density difference between the upper and bottom layer reached up to 5.03 sigma T units. A slight increase in turbidity was detected close to the bottom. No effect of the brine was detected on dissolved oxygen concentration in seawater nor in chl-a concentrations. Chl-a was natural for the area and seasonally dependent (Figure 2), contrary to the observations at the Ashkelon discharge site. In a few instances, particulate iron in seawater was higher than background, similar to the findings at Ashkelon. infauna assemblages The infauna assemblages were studied in 2004 prior to the plant operation and since September 2008. The number of specimens collected at two stations (brine discharge and background) and the relative distribution are depicted in Figure 3. September 2008 was very unusual, with high abundance and high polychaete worms contribution (67%). Two of the three replicates sampled at the outfall were | 28 | Desalination & Water Reuse | February-March 2012 found inordinately rich in opportunistic taxa (biological groupings) such as pilargid and spionid polychaetes, and Erytrean alien mollusks such as Rhinoklavis kochi, Retusa desgenettii, Diplodonta bogii and Strombus persicus. A similar increased contribution of polychaetes at the brine outfall was detected in September 2010 (57%), while in September 2009 the distribution showed a preference to the crustaceans (74%), similar to 2004 (63%), prior to brine discharge. In the spring surveys, there were differences in abundance and relative contribution between the brine disposal site and the background station, but less defined than in the fall. At Ashkelon the IEC monitoring program did not detect an effect on the benthic community, except for a slight decrease in numbers at the outfall 3,16,17. It may be that the high-energy environment, due to the cooling-waters discharge, masks any possible effect of brine and coolingwater discharge. Hypersalinity was shown to affect benthic organisms in certain areas while at others, no effects were detected. The Mediterranean seagrass Posidonia oceanica and associated organisms are highly sensitive to increases in salinity 9,11,13, while other seagrasses are more tolerant to hypersalinity stress 7,12. Increased salinity changed the benthic community at the southeastern Mediterranean coast of Spain from a mixed Polychaeta, Crustacea and Mollusca to one dominated by nematodes 18, while no effect was found in the northwest Mediterranean 10 nor in southwest Florida 19. Macroalgal meadows declined and echinoderms disappeared near the outfall of the Dhekelia SWRO in Cyprus 20. Operative recommendations on salinity levels were set out in some areas. For example, to protect P oceanica, salinity should not exceed 38.5 (around 1.3% of the natural background) for more than 25% of the time annually and not to exceed 40 for more than 5% of the time 13. In western Australia, the median increase in salinity should be less than 5% from background (��� S = 1.5), within 1.2 units of ambient levels within 50 m of the discharge point and within 0.8 units of background levels within 1,000 m of the discharge point. future outlook The study of the marine environmental footprint of SWRO plants is at its fitful start. The combined effects of SWRO

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