Surgical Instrument Washer Disinfectors must rinse using purified water, de-ionized water, or reverse osmosis rinse water.
Process utilizing specially-manufactured ion exchange resins which remove ionized salts from water can theoretically remove 100% of salts. Deionization typically does not remove organics, virus or bacteria, except through “accidental” trapping in the resin and specially made strong base anion resins which will remove gram-negative bacteria. Deionized water (DI water or de-ionized water) also spelled deionized water, see spelling differences) is water that lacks ions, such as cations from sodium, calcium, iron, copper and anions such as chloride and bromide. This means it has been purified from all other ions except H3O+ and OH−, but it may still contain other non-ionic types of impurities such as organic compounds. This type of water is produced using an ion exchange process. Deionized water is similar to distilled water, in that it is useful for scientific experiments where the presence of impurities may be undesirable. Reverse osmosis (RO) is the process of pushing a solution through a filter that traps the solute on one side and allows the pure solvent to be obtained from the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure. This is the reverse of the normal osmosis process, which is the natural movement of solvent from an area of low solute concentration, through a membrane, to an area of high solute concentration when no external pressure is applied. The membrane here is semipermeable, meaning it allows the passage of solvent but not of solute. The membranes used for reverse osmosis have a dense polymer barrier layer in which separation takes place. In most cases the membrane is designed to allow only water to pass through this dense layer while preventing the passage of the solute (such as salt). This process requires that a high pressure be exerted on the high concentration side of the membrane, usually 2–14 bar (30–200 pounds per square inch) for fresh and brackish water, and 40–70 bar [(600–1000 psig)] for seawater, which has around 24 bar (350 psi) natural osmotic pressure which must be overcome. Water purification is the removal of contaminants from raw water to produce drinking water that is pure enough for human consumption or for industrial use. Substances that are removed during the process include parasites ( such as Giardia or Cryptosporidium) , bacteria, algae, viruses, fungi, minerals (including toxic metals such as Lead, Copper etc.), and man-made chemical pollutants. Many contaminants can be dangerous—but depending on the quality standards, others are removed to improve the water's smell, taste, and appearance. A small amount of disinfectant is usually intentionally left in the water at the end of the treatment process to reduce the risk of re-contamination in the distribution system. Many environmental and cost considerations affect the location and design of water purification plants. Groundwater is cheaper to treat, but aquifers usually have limited output and can take thousands of years to recharge. Surface water sources should be carefully monitored for the presence of unusual types or levels of microbial/disease causing contaminants. It is not possible to tell whether water is safe to drink just by looking at it. Simple procedures such as boiling or the use of a household charcoal filter are not sufficient for treating water from an unknown source. Even natural spring water—considered safe for all practical purposes in the 1800s—must now be tested before determining what kind of treatment is needed.
Surgical Instrument Washer Disinfector Washing Purified Water Rinsing Treatments: de-ionized water and reverse osmosis rinse water.
The manufacturers of Surgical Instruments unanimously recommend using Neutral pH chemicals when cleaning surgical Instruments. If the water is acidic, lime or soda ash is added to raise the pH. Lime is the more common of the two additives because it is cheaper, but it also adds to the resulting water hardness. Making the water slightly alkaline ensures that coagulation and flocculation processes work effectively and also helps to minimize the risk of lead being dissolved from lead pipes and lead solder in pipe fittings. The pH should approximate 7 when being used to clean surgical instruments.
pH is a logarithmic measurement of proton presence; the true pH of deionized water is 7.0, because the ionization constant of water (KW) ~ 10-14, so p[KW] = 14, and pH + pOH = p[KW]. In practice, the indication from chemical indicators can give a value of usually between pH 5.0 and pH 9.0 depending on the indicator used (the indication being the ions introduced by the indicator itself, its solvent and its impurities). Electronic pH meters will output an unpredictable value since the absence of ions in the liquid means that the two parts of the electrode are insulated from each other and thus would generate no EMF. In practice since absolutely pure water is an unattainable goal, the liquid will contain a very small amount of ions, but the current this would allow the probe to generate will be far smaller than that required to operate the metering circuit. pH meter electrodes should not be immersed in deionized water for prolonged periods as the lack of any ions 'sucks' them out of the electrode degrading its performance. Deionized water should be used for cleaning only rarely as the effect is cumulative. Electrodes should be cleaned using proper cleaning solution (usually very acidic), and rinsed between samples in a pH neutral liquid such as tap water or pH 7.0 buffer solution (but ideally in the next sample to be tested). Deionized water will quickly acquire a pH when exposed to air. Carbon dioxide, present in the atmosphere, will dissolve in the water, introducing ions and giving an acidic pH of around 5.0. The limited buffering capacity of DI water will not inhibit the formation of carbonic acid H2CO3. Boiling the water will remove the carbon dioxide to restore the absence of a pH value.
Disinfection is normally the last step in purifying drinking water.
Water is disinfected to destroy any pathogens which pass through the filters. Possible pathogens include viruses, bacteria, including Escherichia coli, Campylobacter and Shigella, and protozoans, including G. lamblia and other Cryptosporidia. In most developed countries, public water supplies are required to maintain a residual disinfecting agent throughout the distribution system, in which water may remain for days before reaching the consumer. Following the introduction of any chemical disinfecting agent, the water is usually held in temporary storage often called a contact tank or clear well to allow the disinfecting action to complete.
Chlorine is a strong oxidant that kills many micro-organisms. Because chlorine is a toxic gas, there is a danger of a release associated with its use. This problem is avoided by the use of sodium hypochlorite, which is either a relatively inexpensive solid that releases free chlorine when dissolved in water or a liquid (bleach)that is typically generated on site using common salt and high voltage DC. Handling the solid, however, requires greater routine human contact through opening bags and pouring than the use of gas cylinders which are more easily automated. The generation of liquid sodium hypochlorite is both inexpensive and safer than the use of gas or solid chlorine. Both disinfectants are widely used despite their respective drawbacks. A major drawback to using chlorine gas or sodium hypochlorite is that they react with organic compounds in the water to form potentially harmful levels of the chemical by-products trihalomethanes (THMs) and haloacetic acids, both of which are carcinogenic and regulated by the U.S. Environmental Protection Agency (EPA). The formation of THMs and haloacetic acids is minimized by effective removal of as many organics from the water as possible before disinfection. Although chlorine is effective in killing bacteria, it has limited effectiveness against protozoans that form cysts in water. (Giardia lamblia and Cryptosporidium, both of which are pathogenic). 2. Chlorine dioxide is another fast-acting disinfectant. It is, however, rarely used, because it may create excessive amounts of chlorate and chlorite, both of which are regulated to low allowable levels. Surgical Instrument Washer Disinfectors must rinse using purified water, de-ionized water, or reverse osmosis rinse water.