Water the Universal Solvent

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Water The Universal Solvent

Ever changing and Universally Different

QLD SRACA September 2012

Water the universal solvent

� Water is the most fundamental requirement for your cleaning, thermal disinfection and autoclaving processes

� The need to for suitable quality water to be used for instrument reprocessing has historically been ignored or not appreciated.

Universally different ever changing

� Waters “aint” waters

� The solutes contained in water differ from region to region and they change over time

� The changing solute matrix changes the character of water and the way it interacts / impacts on materials exposed to it.

Overview

� We will look at some of the possible variations in water quality both by region and over time

� Look at how some of the adverse water quality can impact instrument quality

Objectives

� Understand that water quality changes both by region and over time

� Understand it is essential to monitor water quality on site at point of use

Water the universal solvent

Water

Detergent/chemistry

Cleaning solution Chemistry < 1%

Neutralizing Solution Chemistry < 0.3%

Rinsing solution Chemistry <0.03%

Autoclave = 100% water (or it should be)

What is the recommended water quality

Recommendations for water quality taken from RKI “red book”

and are based on DIN EN 285 feed water quality for boilers

Common impurities in water

What should we monitor

� What elements/parameters should we monitor at the point of use.

� Which of the parameters tell most about the water suitability for use in CSSD

� Conductivity or total dissolved solids (TDS)

� The most telling parameter, captures the most information

� conductivity increases with increasing dissolved salts

� Chloride

� (chromomorphic salt - #1 suspect for pitting and crevice corrosion)

� Hardness

� Alkalinity & pH

� If there is appreciable alkalinity you should monitor temporary hardness (Bicrabonate)

� Temporary hardness gives rise to elevated pH in the thermal rinse

Why should we monitor?

� We need to monitor at site level because water changes from region to region and over time

� In June this year urban utilities put out a notification of a predicted spike of 1000-1100 µs/cm (approx 600 TDS). QUU expected the elevated conductivity to be present in the water for several days

� The following slides sets out the conductivity of mains water asmeasured coming into hospitals at various localities around Qld.

� Do you remember the recommendations for conductivity for water used for instrument reprocessing and for boiler feed water

� Answer = 5 µs/cm although experience suggests that 15 µs/cm should be well tolerated

� Source RKI red book 9th edition and DIN EN 285 (2006)

John Flynn Hospital Gold Coast

Holy Spirit Northside

Mater Brisbane

Mater Bundaberg

Mt Isa

Rockhampton Base

Toowoomba Hospital

Cairns Base

Brisbane Drinking water quality

Brisbane Drinking water quality

Gold Coast City Council 1st July 2011 to 39 June 2012

Ipswich Drinking water quality

Ipswich Drinking water quality

SEQ Water Grid issues monthly quality reports for five zones

Compare with

my home town

Melb water Dams

Compare with my

home town

City west waterMelbourne

� TDS is measured by conductivity

� Increasing the level of dissolved solids in water increases the ability of water to conduct an electrical current, which is measured using a conductivity meter or TDS meter.

� Recommended Conductivity for final rinse water (at 25 °C)* ≤ 5 μS/cm

Experience has shown that conductivity of approximately 15 μS/cm can be tolerated.

Conductivity & Total Dissolved solids

� TDS comprises all the salts and impurities dissolved in water

� Includes � Hardness (salts of Ca Mg Ba precipitate as the carbonate,

phosphate, hydroxide or sulfate)

� All additional impurities which do not readily precipitate eg Sodium, Potassium, Chlorides & nitrates

� Increasing conductivity = increasing salt & TDS � Associated with any or all of the following

� Increasing corrosion

� Increasing hardness & scale

� Increasing alkalinity


Water Marks

Water Marks

Any dissolved solids in the final rinse will produce water marks when the water beads evaporate. If the salt contains chloride its bad news for steels



� The presence of chloride in the high temperature phases of a wash program is one of the most notable causes of pitting and crevice corrosion on stainless steel instruments

� WFHSS guidelines on chloride ≤ 2 mg/l in final rinse

Chlorides

Pitting

Chloride induced pitting

Crevice Corrosion

Chloride induced pitting & crevice corrosion

Hardness, Temporary Hardness and Alkalinity

� Everybody knows hardness is responsible for making scale

� However the related parameters of temporary hardness (Bicarbonate hardness) & alkalinity pose some very specific problems for both thermal disinfection and autoclaving which are less understood and even more problematic for sterilizing departments


� If water contains bicarbonate (temporary hardness) and is heated then the following reaction occurs

� 2HCO3- + Heat = CO2↑↑↑↑ + H2O + CO3

2-

� The formation of carbonate (CO32- ) in water as a result of

heating produces two undesirable effects for the liquid medium:� An alkaline shift in the pH of the water

� Precipitation of “temporary hardness” to form carbonate scale.

� The alkaline shift caused by the formation of free carbonate in the high temperature thermal disinfection cycle will strip color from anodized aluminum and powder natural aluminium


� The presence of free carbonate in the thermal disinfection cycle can elevate the pH to 10 or higher

� Carbonate at high temp is corrosive to aluminum and anodised surfaces

pH 8 pH 9 pH 10 pH11


� If water contains bicarbonate (temporary hardness) and is heated then the following reaction occurs

� 2HCO3- + Heat = CO2↑↑↑↑ + H2O + CO3

2-

� The production of Carbon Dioxide CO2↑↑↑↑in a boiler has 2 very undesirable effects on the steam/vapor medium

� CO2 is a non-condensable gas

� Presence of non-condensable gas in the steam means loss of sterilizing efficiency

� Some of the CO2 combines with steam condensate to form Carbonic acid producing acid steam

� Acid steam is a primary cause of corrosion in steam lines

� Have you ever seen rust in the autoclave or on top of your wraps???


� WFHSS recommend Silicates (SiO2) ≤ 1 mg/l

� Silica , silicic acid in soft water results in staining & discoloration of steelsurfaces

� Silica levels being reported in Brisbane drinking water are levels that can cause significant staining

Silica

Typical silica discoloration in the rinsing chamber and on the surface of the instrument caused by cleaning agent containing silicate, or excessive levels of silica in the water.

Silica

Water The Universal Solvent

Ever changing and Universally Different

QLD SRACA September 2012

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Water the Universal Solvent