UV treatment

UV treatment is the most common NDMA removal technique. However, treatment can employ UV fluences near 1000mJ/cm2, nearly an order of magnitude above those employed for disinfection [3]. NDMA exhibits a strong absorption band at 227 nm (e — 7000 M—1 cm— 1) associated with a p — p* transition. Laboratory studies indicate that low- and medium-pressure

Table 6 Literature studies on NDMA rejection by RO and tight NF membranes

Rejection of NDMA (%)

Membrane

MWCOa

Inlet NDMA concentration (ng/L)

Outlet NDMA concentration (ng/L)

Source

Laboratory study —

distilled water matrix

54

RO (ESPA3)

2001

200

92

[87]

70

RO (LFC3)

N/A

200

60

[87]

61

RO (BW-30)

N/A

200

78

[87]

Field studies at water reuse facilities (pilot and full scales) — pre-treated

secondary wastewater matrix

24-56

RO (ESPA2)

250-5002

18-57

14-41

[86]

32

RO (ESPA2)

250-5002

30

20

[39, 85]

40-65b

RO (ESPA2)3

250-5002

25-100

12-50

[40]

42-50b

RO

N/A

50-70

30-45

[40]

10-70b

RO

N/A

200-330

100-170

[40]

50

RO

N/A

N/A

N/A

[3]

~ 50

RO (TFC)

N/A

20-170 (wastewater concentration)

[84]

30

ULPRO (TFC-HR)

N/A

60

40

[39, 85]

50-55

ULPRO (TMG-10)

1004

20-40

10-20

[39, 85]

42-47

NF (NF90)

3005; 2006

10-20

4-12

[39, 85]

N/A means data not available.

a MWCO sources are (1) Fonseca et al. [93], the authors classified this membrane as NF. (2) Estimation in Kim et al. [94]. (3) Plumlee et al. [86]. (4) Drewes et al. [95].

(5) Kim et al. [94]. (6) DOW-Filmtec. b Numbers were approximated from graphs.

N/A means data not available.

a MWCO sources are (1) Fonseca et al. [93], the authors classified this membrane as NF. (2) Estimation in Kim et al. [94]. (3) Plumlee et al. [86]. (4) Drewes et al. [95].

(5) Kim et al. [94]. (6) DOW-Filmtec. b Numbers were approximated from graphs.

lamps exhibit comparable photonic efficiencies for NDMA degradation [99]. Addition of 100mg/L hydrogen peroxide (H2O2) to promote hydroxyl radical (OH*) formation results in no significant benefit regarding NDMA degradation. However, some wastewater recycling facilities employ a UV/ H2O2 advanced oxidation process (AOP) downstream of RO membranes, because of the combination of UV for NDMA removal and OH* for destruction of other contaminants that may pass through the membranes.

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