1 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 Detergent/chemistry Cleaning solution Chemistry < 1% Neutralizing Solution Chemistry < 0.3% Water 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 as measured 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 9 th 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 1 st 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 water Melbourne
Conductivity & Total Dissolved solids 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
Conductivity & Total Dissolved solids 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 Water Marks Water Marks
Conductivity & Total Dissolved solids
Chlorides 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
Chloride induced pitting Pitting
Chloride induced pitting & crevice corrosion 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
Hardness, Temporary Hardness and Alkalinity If water contains bicarbonate (temporary hardness) and is heated then the following reaction occurs 2HCO 3 - + Heat = CO 2 + H 2 O + CO 3 2- The formation of carbonate (CO 3 2- ) 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
Hardness, Temporary Hardness and Alkalinity 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
Hardness, Temporary Hardness and Alkalinity If water contains bicarbonate (temporary hardness) and is heated then the following reaction occurs 2HCO 3 - + Heat = CO 2 + H 2 O + CO 3 2- The production of Carbon Dioxide CO 2 in a boiler has 2 very undesirable effects on the steam/vapor medium CO 2 is a non-condensable gas Presence of non-condensable gas in the steam means loss of sterilizing efficiency Some of the CO 2 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???
Hardness, Temporary Hardness and Alkalinity
Silica WFHSS recommend Silicates (SiO2) 1 mg/l Silica, silicic acid in soft water results in staining & discoloration of steel surfaces 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.
Water The Universal Solvent Ever changing and Universally Different QLD SRACA September 2012