5 Seawater Reverse Osmosis Desalination System
5.1 General Requirements
5.1.1 Spiral wound composite membrane should be used for SWRO unit.The inflow water of spiral wound polyamide composite membrane should comply with the provisions in Table 5.1.1.
Table 5.1.1 Inflow water specification of polyamide composite membrane for SWRO unit
Note:the inflow water specification refers to that at the cartridge filter inlet.
5.1.2 The design inflow water temperature of the SWRO unit should not be lower than 10℃and shall not exceed 40℃.
5.1.3 The salt rejection ratio of the SWRO unit should comply with the following provisions:
1 It shall be no less than 99.5% within 1 year of operation（at 20℃）；
2 It shall be no less than 99.0% within 3 years of operation（at 20℃）.
5.1.4 The salt rejection ratio of the SWRO unit shall be calculated using the following formula:
Where:
R——salt rejection ratio（%）；
Cp——product water salt content（mg/L）；
Cf——seawater salt content（mg/L）；
5.1.5 The recovery ratio of the SWRO unit shall be determined according to the inflow water quality，pretreatment process，membrane element characteristics and project investment，and should be controlled within 35%-55%.The recovery ratio shall be calculated using the following formula:
Where:
Y——recovery ratio（%）；
Qp——producing water flow（m3/h）；
Qf——inflow water flow（m3/h）.
5.1.6 SWRO membrane with low energy consumption shall be used when output water quality specification can be met.
5.1.7 Design of the SWRO desalination system shall comply with the relevant provisions in the current industrial standard DL/T 5068 Technical Code for Designing Chemistry of Fossil Fuel Power Plants.