Comparison of pre-treatment methods of seawater prior to RO desalination with regard to boron and humic acid removal

• Main Author: He, Qihui.
• Other Authors: Chui, Peng Cheong
• Format: Final Year Project
• Language: English
• Published: 2008
• Subjects: DRNTU::Engineering::Environmental engineering::Water treatment
• Online Access: http://hdl.handle.net/10356/14143
• Institution: Nanyang Technological University

Pretreatment of seawater is a very crucial process, especially so prior to RO desalination. In recent years, one major problem faced is the high boron content of the permeate water after RO treatment. For this project, we would find out if the conventional methods of pretreatment are sufficient to counter this problem. If not, are there any industrial available methods for removal of boron? Conventional pretreatment methods include that of coagulation and flocculation. In the experiments conducted, coagulation and flocculation process does not allow any boron removal. However, it is possible to remove an approximate 10% of TOC using this method. Membrane filtration for pretreatment using MF or UF membranes, which is getting increasingly popular in recent years, is also not able to remove boron. Similarly, it is also possible to reduce the same percentage of TOC as compared to coagulation method. Granular Activated Carbon (GAC) method is a comparatively more under-rated method of pretreatment. However, it has a substantial boron removal to the recommended WHO level of 0.5mg/L as well as a high TOC removal of approximately 80%. Ion-exchange resin can guarantee almost 100% removal of boron present in seawater, however, due to the nature of the resin, TOC leaching might prevail. All the pretreatment methods tested achieved very good reduction in physical parameters such as turbidity, color. Membrane filtration has the best turbidity removal of less than 0.2 NTU and GAC method has the best removal of TDS of up to 15%.