3. Background
New Drinking Water Directive 98/83/EC
November 1998
THM, As and Cryptosporidium
Question over conventional technologies
Ultrafiltration (UF) and Microfiltration (MF)
membrane technologies
4. Background
decrease in membrane costs
development of higher flux membranes
better understanding of process parameters
automation potential
simplicity of operation
more stringent water quality requirements, e.g.
Cryptosporidium
5. THM
Nanofiltration (NF)
Combined Coagulation and MF or UF
Operational benefits
– increased permeate flux, reduced backflushing,
reduced chemical cleaning
eliminating the penetration of colloidal material
into the pores
modification of the deposit characteristics
6. Without Coagulation With Coagulation
Reduced pore
penetration
More porous
cake
7. Effect of Coagulation on TMP Development
100
90
80
70
60
TMP (kPa)
50 No Coagulation
With Coagulation
40
30
20
10
0
0 1 2 3 4 5 6 7 8
Days Run
11. Effect of pH on As (V) Removal
120
100
80
% Removal
60
Alum (0.06mM)
40 Fe (0.03mM)
20
0
4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9
pH
12. Arsenic
ferric and aluminium coagulation can remove
As (V)
The removal by aluminium sulphate is clearly
related to the pH
iron (III) hydroxide is able to operate over a
much wider pH range
13. % Removal of As (V) at Different Ferric Chloride Doses at pH 7
120
100
80
% Removal
60
40
20
0
0.000 0.020 0.040 0.060 0.080 0.100 0.120 0.140
Metal Concentration (mM as Fe)
14. % As (III) Removal for Alum and Ferric Chloride
100
90
80
70
% Removal
60
% Rem Fe (pH 7)
50
% Rem Al (pH 7)
40
30
20
10
0
0 0.05 0.1 0.15 0.2
Metal Concentration (mM)
15. Process schematic for combined coagulation and MF or UF
for arsenic removal
Coagulant pH 7
MF or UF
Treated Water
Pre-oxidation Flocculation
Waste
16. Arsenic
As (V) more readily removed than As (III)
As (III) not removed by Aluminium Sulphate
Pre-oxidation will enhance removal
Chlorine, ozone or permanganate
A significant concern for any arsenic removal
process is waste disposal for arsenic-laden
sludges
17. Cryptosporidium
Conventional treatment processes are
susceptible to the passage of Cryptosporidium
into the drinking water supply
MF and UF offer significant advantages due to
barrier nature of the processes
18. Principles of Operation of Immersed Membrane
Permeate
Recovery
QF
Feed Qf QF − QP
Y=
Immersed QF
membranes
Qbp
Membrane tank
Air QP
injection Purge
22. USF Memcor CMF-S
Liquid backwash
plus air scour within
membrane module
23.
24. Key Benefits Drinking Water
Retrofitting / upgrading existing plants by
immersion of the membranes in clarifiers
or sand filters
or contact tanks
or backwash holding tanks
25. Conclusions
Microporous membranes can be used to ensure
that companies comply with the changes under
the new drinking water regulations
Combining coagulation with either a MF or UF
system can enhance their performance in terms
of their removal capabilities
26. Conclusions
Performance associated with much higher
pressure driven processes can be achieved using
low-pressure membrane processes by
combining coagulation with MF or UF
The barrier nature of MF and UF membranes
combined with removal of contaminants with
coagulation means that multiple drivers can be
met in on stage
27. Summary
Question over RGF efficacy - ripening,
breakthrough and transience (flow changes)
MF/UF offer a more secure barrier
Technology is maturing
Recent innovations make further adoption more
likely
