Transcript Présentation PowerPoint

RO Water..New standards brings new
concerns
Presentation Overview
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Water quality requirement of draft
AS/NZS 4187
Issues and concerns in a poorly
designed water treatment plant
Design to achieve compliance
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1.
Water quality requirement of draft
AS/NZS 4187
Final Rinse Water Quality Standards
o Draft AS / NZS 4187
o HTM2030
o ISO 15883 Part 4
o CFPP 01-01
o NHS C30
o HTM 01 06 (Draft)
PARAMETER
MAX ALLOWABLE
Bacteria Total Viable Count
<100 CFU / 100 ml
Endotoxin
<0.25 EU/ml
Inorganic purity (Conductivity)
<30 µS/cm
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Definition of Terms
Biofilm
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Microorganisms in fluid colonise surfaces results in biofilm
formation even when levels of microbial contamination are low.
Microorganisms living within biofilms produce a slime matrix which
protects them against disinfection. Therefore all strategies for
microbial control of the water treatment system should be
proactive in order to limit microbial growth and biofilm formation
(biofouling).
In order to control the formation of biofilm within a water treatment
system, disinfection procedure should be applied from the start of
the operation.
Once formed biofilm is difficult, if not impossible, to eradicate.
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Endotoxin
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“Endotoxin” is a toxin that is released from the cell surface of Gramnegative bacteria either through its growth and cell division (small
amounts) or on the cell's death (large quantities).
Chemical disinfection, steam sterilization or hot water sanitisation of
equipment, which are contaminated with Gram-negative bacteria, will
generate endotoxins.
Endotoxins when introduced into human body, can cause a fever-like
reaction and other adverse effects.
They are not readily inactivated by chemicals. They are extremely heat
stable, remaining viable even after conventional autoclaving, and have
been shown to require a temperature of 180°C for at least 3 h or 250°C for
30 min to be destroyed.
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Endotoxin Continue…
A paper by I. P. Lipscomb et al, ‘Comparative Study of Surgical Instruments
from Sterile-Service Departments for Presence of Residual Gram Negative
Endotoxin and Proteinaceous Deposits’ published in the Journal of Clinical
Microbiology (2006), 44 states:
In studies of patients admitted to a general hospital in UK, 17.6% displayed
bacteremic episodes, with the most prevalent being caused by
Escherichia coli, Klebsiella pneumoniae, Enterobacter, and Salmonella.
These gram-negative bacteria have lipopolysaccharide molecules or
endotoxin on their cell surface, which has been associated with systemic
inflammatory infections, such as sepsis.
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3.
Issues and concerns in a
poorly designed water
treatment plant
Issues and concerns of a poorly designed water
treatment plant
(Bio-Film in Plastic Pipe Work)
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(Dead Leg Between RO & Tank)
A. Pre-treatment
(“Dam” Type Endotoxin Filter)
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(Poorly Designed Plastic Tank)
B. RO Unit
C. Storage Tank
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(Heat Build Up)
D. Distribution System
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4.
In Field Testing – Biofilm
Growth
Biofilm Formation Testing
Study Methodology
The number of colony-forming units (CFU/m2) were determined and the
piping was examined under a scanning electron microscopy (SEM) in order
to visualise potential biofilm residues on the pipe internal surface.
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At 3 water treatment systems with hygienically designed RO unit,
treated water distribution loop piping with PE-Xa with hot water
sanitisation (HWS) were used. Results were recorded after:
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HWS once per week
HWS twice per week
HWS 3 times per week
One (1) water treatment system with hygienically designed RO unit,
treated water distribution loop piping with PE-Xa without hot water
sanitisation.
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Results
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SEM Results
No disinfection
2 x HWS / week
1 x HWS / week
3 x HWS / week
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5.
In Field Testing – Water Quality
Compliance Testing
Compliance Testing at Two Hospitals in QLD
Study Methodology
Water treatment systems at two different hospitals in Queensland were
tested for compliance:
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Case Study 1 – Hospital with a industrial water treatment plant (included
RO, off the shelf 1,000 l tank with a lid, pump and ringmain) which was
not designed for bacterial control
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Case Study 2 – Hospital with a purpose built water treatment plant to
meet EN15883 compliance
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Results – Case Study 1
Parameter
Measured Value
Draft AS/NZS 4187*
6.19
5.5 to 8.0
2
< 30
Total Dissolved Solids (mg/100ml)
< 10
<4
Total Hardness, CaCO3 (mg/l)
<1
< 50
Chloride, Cl (mg/l)
<1
< 10
Heavy metals, determined as Lead, Pb (mg/l)
0.002
< 10
Iron, Fe (mg/l)
< 0.05
<2
Phosphate, P2O5 (mg/l)
< 0.02
< 0.2
0.4
< 0.2
Total viable count (TVC)
at 22 oC (cfu/100 ml)
At 37 oC (cfu/100 ml)
<100
2,000
< 100
< 100
Bacterial endotoxins (EU/ml)
< 0.25
< 0.25
Degree of acidity (pH)
Conductivity at 25 oC (µS/cm)
Silicate, SiO2 (mg/l)
* - Maximum permitted values for final rinse
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Results – Case Study 2
Parameter
Measured Value
Draft AS/NZS 4187*
Degree of acidity (pH)
6.01
5.5 to 8.0
Conductivity at 25 oC (µS/cm)
<1
< 30
Total Dissolved Solids (mg/100ml)
< 10
<4
Total Hardness, CaCO3 (mg/l)
<1
< 50
Chloride, Cl (mg/l)
<1
< 10
Heavy metals, determined as Lead, Pb (mg/l)
0.002
< 10
Iron, Fe (mg/l)
< 0.05
<2
Phosphate, P2O5 (mg/l)
< 0.02
< 0.2
0.2
< 0.2
Total viable count (TVC)
at 22 oC (cfu/100 ml)
At 37 oC (cfu/100 ml)
<100
100
< 100
< 100
Bacterial endotoxins (EU/ml)
< 0.25
< 0.25
Silicate, SiO2 (mg/l)
* - Maximum permitted values for final rinse
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6.
Conclusion
Conclusion – Design of RO unit to meet
compliance
Stage by stage removal of impurities
Conclusion – Design of RO unit to meet
compliance
It should be emphasised that if the rinsewater systems (i.e. RO system) is not
designed adequately for the control of bacteria (with a minimum ringmain
velocity, minimum dead leg for bacteria / biofilm growth) and is not regularly
disinfected and validated (i.e. Water samples should be routinely taken to
demonstrate compliance), meeting the draft AS/NZS 4187 microbial
specification is a “hit and miss”.
Instead, the proliferation of bacteria is not uncommon in a poorly designed and
maintained water treatment and distribution system.
The system has to be designed to be simple and easily sanitised (chemically or
using heat) by the CSSD manager when or if required. This is critical as there
might be times when a unexpected high microbial count is found in the town
water supply (can occur in an event of a natural disaster such as floods), the
CSSD manager should be able to carry out the sanitisation process to resolve
this (without relying on the equipment supplier).
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Thank you for your attention
Veolia Water Technologies
3B Lenton Place
North Rocks NSW 2151
Tel. + 61 2 8832 4500