Utilization of reverse osmosis (RO) for reuse of MBR-treated wastewater in irrigation-preliminary tests and quality analysis of product water.

Membrane bioreactor (MBR) effluent collected from a wastewater treatment plant installed at an industrial zone was used for reverse osmosis (RO) membrane tests in the laboratory. For this, two different GE Osmonics RO membranes (AK-BWRO and AD-SWRO) were employed. The results showed that AK-brackish water reverse osmosis (AK-BWRO) and AD-seawater reverse osmosis (AD-SWRO) membranes have almost similar rejection performances regarding analyzed parameters such as conductivity, salinity, color, chemical oxygen demand (COD), and total organic carbon (TOC). On the other hand, these membranes behaved quite differently considering their permeate water flux at the same applied pressure of 10 bar. AD-SWRO membrane was also tested at 20 bar. The results revealed that AD-SWRO membrane had almost the same rejections either at 10 or at 20 bar of applied pressure. Compared with irrigation water standards, AK-BWRO and AD-SWRO gave an effluent with low salinity value and sodium adsorption ratio (SAR) which makes it unsuitable for irrigation due to the infiltration problems risi0ng from unbalanced values of salinity and SAR. Combination of MBR effluent and RO effluent at respective proportions of 0.3:0.7 and 0.4:0.6 for AK-BWRO and AD-SWRO, respectively, are the optimum mixing ratios to overcome the infiltration hazard problem. Choice of less-sensitive crops to chloride and sodium ions is another strategy to overcome all hazards which may arise from above suggested mixing proportions.

Long-term monitoring of the impact of a capture-based bluefin tuna aquaculture on water column nutrient levels in the Eastern Aegean Sea, Turkey.

Capture-based aquaculture of Atlantic bluefin tuna in the Mediterranean has been expanding rapidly but little is known about its environmental impact. In order to understand the consequences of this new sector, long-term monitoring is needed. For this purpose, we investigated the impact of a capture-based tuna farm located in the Gerence Bay (Aegean Sea) on the water column on a seasonal basis from 2005 to 2008, where in the water column, temperature, salinity, pH, dissolved oxygen, nutrients (nitrite, nitrate, ammonium, and phosphate), and chlorophyll a, in the sediment organic carbon variables were measured. Although highest nutrient concentrations were observed at the cage station as compared to the two controls in the production period, differences were not statistically significant between stations. Monitoring of physico-chemical parameters, nutrients, and chlorophyll a in water column together with organic carbon in sediment did not show detectable impact of fattening of Atlantic bluefin tuna. This was probably caused by strong currents present in the area, location of the cages away from the coast, hence high water depth, controlled feeding, and periodic presence of tuna farming activity in the study area.

Impacts of the fish farms on the water column nutrient concentrations and accumulation of heavy metals in the sediments in the eastern Aegean Sea (Turkey).

We investigated potential effects of the fish farms on water column and sediment around Salih Island in the Gulluk Bay (Aegean Sea, Turkey) where four seasonal samplings were performed from October 2001 to August 2002. One measured physicochemical variables in water column including dissolved oxygen, nutrients (nitrite, nitrate, ammonium, phosphate and silicate), particulate organic carbon (POC) and chlorophyll a. Organic matter, total organic carbon (TOC) and heavy metals (Zn, Cu and Fe) were measured in sediment samples. Although occasional increases in ammonium and chlorophyll a concentrations were observed at the cage stations as compared to the control one, no statistically significant differences were detected among the stations in terms of nutrients, chlorophyll a and POC. On the other hand, significant differences were found in organic matter, TOC and heavy metals (Zn and Fe) of the sediments among the sampling stations. Despite these differences, our results indicate that concentrations of physicochemical variables and heavy metals were within the range of tolerable levels for the marine ecosystem, and the oligotrophic nature of the water column in the study area was able to assimilate organic and inorganic loads caused by the fish farms.