RO Water..New standards brings new concerns

o Water quality requirement of draft AS/NZS 4187

o Issues and concerns in a poorly designed water treatment plant

o Design to achieve compliance

Presentation Overview

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1.

Water quality requirement of draft AS/NZS 4187

Final Rinse Water Quality Standards

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PARAMETER MAX ALLOWABLE

Bacteria Total Viable Count <100 CFU / 100 ml

Endotoxin <0.25 EU/ml

Inorganic purity (Conductivity) <30 µS/cm

o Draft AS / NZS 4187 o HTM2030

o ISO 15883 Part 4 o CFPP 01-01

o NHS C30 o HTM 01 06 (Draft)

2.

Definition of Terms

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Biofilm

o Microorganisms in fluid colonise surfaces results in biofilm formation even when levels of microbial contamination are low.

o 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).

o In order to control the formation of biofilm within a water treatment system, disinfection procedure should be applied from the start of the operation.

o Once formed biofilm is difficult, if not impossible, to eradicate.

o “Endotoxin” is a toxin that is released from the cell surface of Gram-negative bacteria either through its growth and cell division (small amounts) or on the cell's death (large quantities).

o Chemical disinfection, steam sterilization or hot water sanitisation of equipment, which are contaminated with Gram-negative bacteria, will generate endotoxins. 

o Endotoxins when introduced into human body, can cause a fever-like reaction and other adverse effects.

o 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.

Endotoxin

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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.

Endotoxin Continue…

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3. Issues and concerns in a

poorly designed water treatment plant

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Issues and concerns of a poorly designed water treatment plant

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A B C D

(Bio-Film in Plastic Pipe Work) (“Dam” Type Endotoxin Filter)

(Dead Leg Between RO & Tank) (Poorly Designed Plastic Tank) (Heat Build Up)

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A. Pre-treatment B. RO Unit C. Storage Tank D. Distribution System

4.

In Field Testing – Biofilm Growth

Biofilm Formation Testing

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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.

1. 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:

o HWS once per weeko HWS twice per week o HWS 3 times per week

2. 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

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No disinfection 1 x HWS / week

3 x HWS / week2 x HWS / week

5.

In Field Testing – Water Quality Compliance Testing

Study Methodology

Water treatment systems at two different hospitals in Queensland were tested for compliance:• 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

• Case Study 2 – Hospital with a purpose built water treatment plant to meet EN15883 compliance

Compliance Testing at Two Hospitals in QLD

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* - Maximum permitted values for final rinse

Results – Case Study 1

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Parameter Measured Value Draft AS/NZS 4187*

Degree of acidity (pH) 6.19 5.5 to 8.0Conductivity at 25 oC (µS/cm) 2 < 30Total Dissolved Solids (mg/100ml) < 10 < 4Total Hardness, CaCO3 (mg/l) < 1 < 50

Chloride, Cl (mg/l) < 1 < 10Heavy metals, determined as Lead, Pb (mg/l) 0.002 < 10Iron, Fe (mg/l) < 0.05 < 2Phosphate, P2O5 (mg/l) < 0.02 < 0.2

Silicate, SiO2 (mg/l) 0.4 < 0.2

Total viable count (TVC) at 22 oC (cfu/100 ml)At 37 oC (cfu/100 ml)

<1002,000

< 100< 100

Bacterial endotoxins (EU/ml) < 0.25 < 0.25

* - Maximum permitted values for final rinse

Results – Case Study 2

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Parameter Measured Value Draft AS/NZS 4187*

Degree of acidity (pH) 6.01 5.5 to 8.0Conductivity at 25 oC (µS/cm) < 1 < 30Total Dissolved Solids (mg/100ml) < 10 < 4Total Hardness, CaCO3 (mg/l) < 1 < 50

Chloride, Cl (mg/l) < 1 < 10Heavy metals, determined as Lead, Pb (mg/l) 0.002 < 10Iron, Fe (mg/l) < 0.05 < 2Phosphate, P2O5 (mg/l) < 0.02 < 0.2

Silicate, SiO2 (mg/l) 0.2 < 0.2

Total viable count (TVC) at 22 oC (cfu/100 ml)At 37 oC (cfu/100 ml)

<100100

< 100< 100

Bacterial endotoxins (EU/ml) < 0.25 < 0.25

6. Conclusion

Stage by stage removal of impurities

Conclusion – Design of RO unit to meet compliance

Conclusion – Design of RO unit to meet compliance

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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 attentionVeolia Water Technologies

3B Lenton PlaceNorth Rocks NSW 2151Tel. + 61 2 8832 4500