use of microporous membranes for regulatory compliance
TRANSCRIPT
Use of Microporous Membranes Use of Microporous Membranes
for Compliance with the New for Compliance with the New
Drinking Water RegulationsDrinking Water Regulations
Peter Hillis, Research Associate, Peter Hillis, Research Associate,
North West Water LtdNorth West Water Ltd
IntroductionIntroduction
�� BackgroundBackground
�� THMTHM
�� ArsenicArsenic
�� CryptosporidiumCryptosporidium
�� ConclusionsConclusions
BackgroundBackground
�� New Drinking Water Directive 98/83/EC New Drinking Water Directive 98/83/EC
November 1998 November 1998
�� THM, As andTHM, As and CryptosporidiumCryptosporidium
�� Question over conventional technologies Question over conventional technologies
�� Ultrafiltration (UF) and Microfiltration (MF) Ultrafiltration (UF) and Microfiltration (MF)
membrane technologiesmembrane technologies
BackgroundBackground
�� decrease in membrane costsdecrease in membrane costs
�� development of higher flux membranesdevelopment of higher flux membranes
�� better understanding of process parametersbetter understanding of process parameters
�� automation potentialautomation potential
�� simplicity of operationsimplicity of operation
�� more stringent water quality requirements, e.g. more stringent water quality requirements, e.g.
CryptosporidiumCryptosporidium
THMTHM
�� Nanofiltration (NF) Nanofiltration (NF)
�� Combined Coagulation and MF or UFCombined Coagulation and MF or UF
�� Operational benefitsOperational benefits
–– increased permeate flux, reduced backflushing, increased permeate flux, reduced backflushing,
reduced chemical cleaningreduced chemical cleaning
�� eliminating the penetration of colloidal material eliminating the penetration of colloidal material
into the poresinto the pores
�� modification of the deposit characteristicsmodification of the deposit characteristics
Reduced pore
penetration
More porous
cake
Without Coagulation With Coagulation
Effect of Coagulation on TMP Development
0
10
20
30
40
50
60
70
80
90
100
0 1 2 3 4 5 6 7 8
Days Run
TMP (kPa)
No Coagulation
With Coagulation
0.0%
10.0%
20.0%
30.0%
40.0%
50.0%
60.0%
70.0%
80.0%
90.0%
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08
Coagulant dose (mM Fe)
% Removal
%Removal THMFP
%Removal TOC
THMTHM
�� >80% removal of THM>80% removal of THM
�� No floc breakthroughNo floc breakthrough
�� Enhanced membrane operationEnhanced membrane operation
�� Enhanced membrane performanceEnhanced membrane performance
ArsenicArsenic
�� Reverse OsmosisReverse Osmosis
�� Ion ExchangeIon Exchange
�� Lime SofteningLime Softening
�� Adsorption on Granular Ferric HydroxideAdsorption on Granular Ferric Hydroxide
�� Adsorption on Activated Adsorption on Activated AluminaAlumina
�� CoagulationCoagulation
Effect of pH on As (V) Removal
0
20
40
60
80
100
120
4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9
pH
% Removal
Alum (0.06mM)
Fe (0.03mM)
ArsenicArsenic
�� ferric and aluminium coagulation can remove ferric and aluminium coagulation can remove
As (V)As (V)
�� The removal by aluminium sulphate is clearly The removal by aluminium sulphate is clearly
related to the pHrelated to the pH
�� iron (III) hydroxide is able to operate over a iron (III) hydroxide is able to operate over a
much wider pH rangemuch wider pH range
% Removal of As (V) at Different Ferric Chloride Doses at pH 7
0
20
40
60
80
100
120
0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140
Metal Concentration (mM as Fe)
% Removal
% As (III) Removal for Alum and Ferric Chloride
0
10
20
30
40
50
60
70
80
90
100
0 0.05 0.1 0.15 0.2
Metal Concentration (mM)
% Removal
% Rem Fe (pH 7)
% Rem Al (pH 7)
Pre-oxidation
Coagulant pH 7
Flocculation
MF or UF
Waste
Treated Water
Process schematic for combined coagulation and MF or UF
for arsenic removal
ArsenicArsenic
�� As (V) more readily removed than As (III)As (V) more readily removed than As (III)
�� As (III) not removed by Aluminium SulphateAs (III) not removed by Aluminium Sulphate
�� PrePre--oxidation will enhance removaloxidation will enhance removal
�� Chlorine, ozone or permanganateChlorine, ozone or permanganate
�� A significant concern for any arsenic removal A significant concern for any arsenic removal
process is waste disposal for arsenicprocess is waste disposal for arsenic--laden laden
sludgessludges
CryptosporidiumCryptosporidium
�� Conventional treatment processes are Conventional treatment processes are
susceptible to the passage of susceptible to the passage of CryptosporidiumCryptosporidium
into the drinking water supplyinto the drinking water supply
�� MF and UF offer significant advantages due to MF and UF offer significant advantages due to
barrier nature of the processesbarrier nature of the processes
Principles of Operation of Immersed Membranes
Feed
Permeate
Airinjection
Immersedmembranes
Purge
QF
QP
Qf
Membrane tank
Qbp
YQ Q
Q
F P
F
=−
Recovery
The ZeeWeed® Hollow Fibre
The ZW-4000
ZeeWeed® Cassette
Surface area: 370 m2
Dimension:Height: 180 cmWidth: 60 cmDepth: 160 cm
Packing density: 210 m2/m3
USF Memcor CMFUSF Memcor CMF--SS
Filtrate manifold
Clover
Modules
USF Memcor CMFUSF Memcor CMF--SS
Liquid backwash Liquid backwash
plus air scour within plus air scour within
membrane modulemembrane module
Key Benefits Drinking WaterKey Benefits Drinking Water
�� Retrofitting / upgrading existing plants byRetrofitting / upgrading existing plants by
�� immersion of the membranes in clarifiersimmersion of the membranes in clarifiers
�� or sand filtersor sand filters
�� or contact tanksor contact tanks
�� or backwash holding tanksor backwash holding tanks
ConclusionsConclusions
�� Microporous membranes can be used to ensure Microporous membranes can be used to ensure
that companies comply with the changes under that companies comply with the changes under
the new drinking water regulationsthe new drinking water regulations
�� Combining coagulation with either a MF or UF Combining coagulation with either a MF or UF
system can enhance their performance in terms system can enhance their performance in terms
of their removal capabilitiesof their removal capabilities
ConclusionsConclusions
�� Performance associated with much higher Performance associated with much higher
pressure driven processes can be achieved using pressure driven processes can be achieved using
lowlow--pressure membrane processes by pressure membrane processes by
combining coagulation with MF or UFcombining coagulation with MF or UF
�� The barrier nature of MF and UF membranes The barrier nature of MF and UF membranes
combined with removal of contaminants with combined with removal of contaminants with
coagulation means that multiple drivers can be coagulation means that multiple drivers can be
met in on stagemet in on stage
SummarySummary
�� Question over RGF efficacy Question over RGF efficacy -- ripening, ripening,
breakthrough and transience (flow changes)breakthrough and transience (flow changes)
�� MF/UF offer a more secure barrierMF/UF offer a more secure barrier
�� Technology is maturingTechnology is maturing
�� Recent innovations make further adoption more Recent innovations make further adoption more
likelylikely