LPAC

Compatibility of MP membranes and O3

Membranes as O3 contactors

Materials under study

Experimental Procedure

Compatible or not compatible ?

Conclusions

LPAC

Membranes for O3 contacting: Several benefits!

O3 in water treatment:

MP membranes feasible for O3 mass transfer?

production mass

transfer

water

treatment

off-gas

treatment

- Different contactor types, characteristics & performance

- Membrane contactors:• off-gas can be recycled,

• bubble-free,

• scaling,

• moderate to fast mass transfer (high kLa values)

LPAC

Compatibility of MP membranes and O3

Membranes as O3 contactors

Materials under study

Experimental Procedure

Compatible or not compatible ?

Conclusions

LPAC

Original and chemically modified membrane materials under study

MP polymeric ultra-filtration membrane tubes

Membrane test assembly:• PVC outer tube, MP membranes inside

• Water flow inside the membranes, O2/O3 flow outside the membranes

• 1 Assembly with original membrane tubes

1 Assembly with chemically modified membranes

water

O2/O3

LPAC

Compatibility of MP membranes and O3

Membranes as O3 contactors

Materials under study

Experimental Procedure

Compatible or not compatible ?

Conclusions

LPAC

Methods: Ozonation of membrane tubes

Set-up: Batch ozonation of MP membrane tubes

O2

pump

MFC

OG

OS

FC2

FC1

LPAC

Methods: Ozonation of membrane tubes

Experimental conditions:

• 5 pieces from 3 different membrane tubes

• Visual observation of damage + weigth before - after

• Milli-Q water, near-neutral pH, RT

• Ozonation: 3.5 + 7.3 + 6.0 hours, [O3]liq = 8.2–8.6 mg/L

• Monitoring of pH, ORP, conductivity, [O3]gas, [O3]liq, T,

UV/VIS

LPAC

Methods: Test assembly

Test assembly:• Milli-Q water, near-neutral pH, RT

• Water flow: peristaltic pump

• [O3]gas = ~ 50 g/m3

Set-up:

O2

pump

MFC

OG

OS

FC2

FC1

LPAC

Compatibility of MP membranes and O3

Membranes as O3 contactors

Materials under study

Experimental Procedure

Compatible or not compatible ?

Conclusions

LPAC

Ozonation of membrane tubes: clear indication of degradation

Visual observations (after ± 17 hours ozonation):• Dispersion of white particles in solution

• Increased surface roughness, loss of flexibility

Mass balance:

mass loss after ozonation periods points at degradation

UV/VIS + Conductivity:

build-up of degradation products in solution

pH:

decrease in pH caused by formation of carboxylic acids (?)

LPAC

Test assemblies: MP membranes incompatible with O3

Both test assemblies: damage after < 50 minutes O3 flow!

LPAC

Compatibility of MP membranes and O3

Membranes as O3 contactors

Materials under study

Experimental Procedure

Compatible or not compatible ?

Conclusions

LPAC

MP membranes and O3 incompatible

Nor original, neither modified MP ultra-filtration membranes are resistant to O3

MP membranes cannot be used for O3 contacting despite low [O3]liq in disinfection (typically 0.1 – 1 mg/L)

degradation = concentration + exposure !

Ozonated water streams need to be separated from filter units in the dishwashers!