Organics and Salt Rejection in Synthetic Surface Water Solutions

2 Organics and Salt Rejection in Synthetic Surface Water Solutions 

Fulvic acid (FA) was used for rejection experiments, as FA is smaller than HA. Therefore, the rejection due to size of this compound should be lowest. While the NOM is still smaller rhan FA, the impurities in the NOM and the fact that its contents are largely uncharacterised make the use of FA more attractive. 

Preliminary experiments were carried out with the TFC-SR membrane to test the impact of background salt composition on flux and rejection. Rejection results are summarised in Table 7.9. 

As a general trend, in most experiments the rejection increases from sample 1 to 3. This may have occurred for a number of reasons. Firstly, the concentration in the cell increases during filtration. 

Second, the composition of the feed changes as a function of rejection, with the less rejected compound being depleted in the cell. Thirdly, the variation of the membrane charge due to adsorption effects may vary the rejection behaviour of the membranes. 

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