Nanomembranes - Nanotechnologies for Water Environment Applications - page 391

with more than 97% removal for most PhACs (such as naproxen and carbamazepine)
were achieved using NF membrane (NE4040-90-RF, Saehan Industries Inc., Korea) to
treat MBR effluent (Kim et al., 2007), and no PhAC compounds were detectable in most
cases (Asano et al., 2007). The variation in rejection rates could also be related to the
feed concentration as demonstrated by Kimura et al. (2003). A few selected PhACs,
namely, diclofenac, phenacetine and primidone experienced a lower rejection in both NF
(with MWCO of 200 Da) and RO membranes (both are of polyamide TFC materials)
when present at lower feed concentrations. However, the mechanisms involved in
lowering the rejection at lower feed concentrations are still unconfirmed. Therefore,
further investigations will be needed to confirm such trend. A comparison on the
rejection of the mentioned compounds at 100 μg/L and 100 ng/L are presented in Table
12.9 (extracted from Kimura et al., 2003). The rejection rates of an NF membrane (NF-
4040 membrane from Dow/FILMTEC TM , polypiperazine amide thin-film composite
membrane) used for treatment of tertiary treated wastewater is presented in Table 12.10
(extracted from Bellona and Drewes, 2007).

Table 12.10 Rejection rates for NF membrane used for treatment of tertiary treated
effluent (extracted from Bellona and Drewes, 2007).
Constituents Rejection Rate (%)

96

TOC

Conductivity 48

Sodium 40

Potassium 40

Calcium 70

Magnesium 80

Chloride 25

Pharmaceutically Active Compounds (PhACs)
Salicylic Acid 100

Naproxen 90

Gemfibrozil 90

Ketoprofen 78

Carbamazepine 90

The selection of a suitable membrane material for its intended use is also
important to ensure consistency in permeate quality during prolonged process operation.
Polyamide NF MBR was shown to have high treatment efficiency and satisfactory
stability for long-term operation compared with NF MBR made from cellulose acetate