Environmental Engineering Reference
In-Depth Information
with MF membranes that in turn led to a lower TOC in the permeate or feed to RO
membrane. High organic acids rejection from anaerobic effluent was demonstrated using
polyamide NF membranes (ES10 with MWCO 100 Da, Nitto Denko and NF270 with
MWCO 200-300, Dow/FILMTEC
TM
) with an average of 89% rejection (Choi et al.,
2008). This clearly demonstrated the potential of using NF membrane to reduce the
problem of biofouling in RO processes.
Table 12.8
Comparison on the RO feed produced by the conventional secondary
treatment-MF and the MBR (extracted from Qin et al., 2006).
Parameter
ASP-MF
Pilot Scale MBR
pH
6.6-6.8
6.7-6.9
TDS (mg/L)
1
573-703
557-749
TOC
2
6.8-6.9
4.9-5.1
NH
4
+
-N
1.96-5.54
1.0-1.7
NO
3
-
26.6-60.5
6.3-28.4
1
TDS = total dissolved solids.
2
TOC = Total organic carbon.
Table 12.9
Comparison on the rejection of diclofenac, phenacetine and primidone using
NF and RO membranes at feed concentrations of 100 μg/L and 100 ng/L (extracted from
Kimura et al., 2003).
Feed concentration
at 100
μ
g/L
Feed concentration
at 100 ng/L
Molecular
Weight
Compound
Rejection by
NF
Rejection by
RO
Rejection by
NF
Rejection by
RO
Diclofenac
318
0.93
0.95
N/A
0.65
Phenacetine
179
0.19
0.71
0.14
0.50
Primidone
218
0.87
0.84
0.72
0.78
Several projects in the USA are using secondary treated effluent followed by
treatment using MF and NF or RO for subsurface injection into the aquifer (Asano and
Cotruvo, 2007). The salt rejection and the organic removals provided by NF membranes
are able to achieve the water quality required for groundwater recharge (Asano et al.,
2007). In addition, high rejections of emerging contaminants related to groundwater
recharge have been reported using NF. These include non detectable amount of
endocrine disruptors (EDCs) in NF permeate (Drewes et al., 2002) while more than 80%
rejection of pharmaceutically active compounds (PhACs) were reported in NF
membranes (NF-4040 membrane from Dow/ FILMTEC
TM
, polypiperazine amide thin-
film composite (TFC) membrane) (Bellona and Drewes, 2007). Even higher rejections
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