The main factors of environmental impact of desalination can be explained as marine water temperature and GHG (Greenhouse Gas) emission. Most of desalination plants in GCC countries are combined with power plants in which the effluents water temperature is high that could increase the temperature of the surrounding seawater (Khawaji et al, 2008:16). According to Dawoud (2012: 28) reported that in summer the ambient seawater temperature will increase from 35℃ to 41-43℃ on average in the plants vicinity, resulting in the recombination in marine systems since high temperature could be fatal to marine life. In addition, due to the energy consumption, the desalination industry is exacerbating air pollution through CO2，SO2 and NOx emissions, which can be showed in Table 4.
Table 4: CO2，SO2 and NOx emissions of desalination in Oman (million metric tons) | CO2 | SO2 | NOx | 2006 | 31.00 | 8.50 | 65.00 | 2007 | 33.00 | 19.60 | 49.34 | 2008 | 34.00 | 4.19 | 38.44 | 2009 | 36.00 | 4.00 | 37.00 | 2010 | 38.00 | 3.85 | 35.00 |
Source: Dawoud and Mulla (2012: 31-32)
Compared with the CO2 emission of 40.374 and 45.749 (million metric tons) in 2007 and 2008 respectively in Oman (World Bank), the Table 4 illustrates that the quantity of CO2 emission from desalination might contribute to a large proportion of the CO2 emission in this country.
On the other hand, because the main materials of water reuse are wastewater and rainfall, it cannot influence the temperature of the seawater. Additionally, it can be seen in Table 5 that include the CO2，SO2 and NOx emission of water reuse,