Keep your pH in the safe zone
In swimming pool chemistry we disinfect the water not sterilize it. We want the pool safe for swimmers by protecting them from bacteria, virus and parasites otherwise known as pathogens. We cannot kill and keep removed all of these we are simply controlling the pathogens for safe swimming. As humans we build immunity from some contact with pathogens and in a sterile environment this could not happen.
Disinfecting a pool requires a sanitizer to have a specified contact time to kill or destroy the pathogen and then the filter process removes the pathogen from the water. This is why minimum sanitation levels, proper circulation and filtration and regular cleaning of the filters are so important.
Chlorine at 1 ppm and a pH below 8.0 can give an effective kill in most cases of 30 seconds. It is important to have the pH below 8.0 as the neutral charged hypochlorous acid which is formed when chlorine is added to water is more prevalent at lower pH values. The HOCL because it is neutrally charged can penetrate a cell wall easier so we want more of it in the water. At a pH of 8 there is no killing power for sanitizer.
The pathogen can be made harmless by removing them from the water or interrupting their life cycle. When their cell wall or enzymes are disturbed they either die or can no longer reproduce.
Friday, December 2, 2011
How Chloramines Are Formed and the Best Way to Eliminate Them
Chloramines are a nuisance to swimming pool operators and users which need to be eliminated to assure a safe and inviting swimming experience. Preventative measures to keep chloramines at a minimum combined with adequate testing and corrective chemical action by the pool operator can avoid many pool problems resulting from their presence. New technology now enables the pool operator to control chloramines easier and more effectively.
Chloramines are formed when a halogen or chlorine based sanitizer is introduced into the water and reacts or combines with waste such as sweat, urine and ammonia to name a few. The chloramines compounds do not have an effective disinfecting ability and require one hundred more times the contact time to be as effective as free chlorine. These build a chlorine demand which must be met before a residual amount of chlorine or free chlorine can become present for disinfection. If the demand is not met with the amount of chlorine added then more chloramines can be formed.
Foul smelling odor, cloudy water, eye irritation, and skin irritation are a few of the problems that chloramines can cause. These are not desirable in any swimming pool environment and therefore must be controlled or eliminated.
Regular testing for combined chlorine indicates the presence of chloramines. Many quality test kits allow you to test for Free Chlorine then an additional Total Chlorine reading. Free Chlorine is the available chlorine to disinfect the water. Total Chlorine is all chlorine present in the water. To find the combined chlorine reading or chloramines in the water you need to subtract the Free Chlorine from the Total Chlorine reading with the result being the amount of chloramines or combined chlorine in the water. A reading above .2 of combined chlorine lets you know that treatment is needed. If you find that the level of combined chlorine continually is high in your pool then a change in the chemical maintenance may be necessary. This may change with temperature, bather load and other environmental factors.
To decrease the wastes entering the pool it is recommended for bathers to shower before entering the pool water. Although the wastes washed off of one person entering the pool may not seem like much when multiplied by many swimmers it can be a significant amount. Keeping pool decks clean and disinfected can also decrease the amount of wastes entering the pool. Having people that have recently had diarrhea not enter the pool for a period of time and having babies with diapers use swim pants also helps in preventative measures.
If chloramines are detected regularly it may be necessary to increase the amount of chlorine being generated into the pool to help meet the initial demand of wastes and decrease the frequency in which the pool must be treated to remove the chloramines.
To eliminate chloramines the pool water must be treated by raising the pool chlorine level or oxidizing the pool water to chemically break up the chloramines compounds. This is generally referred to as a “shock” treatment or super chlorination, when the free chlorine level is raised to ten times the amount of chloramines present. This has been the standard procedure for many years. This will eliminate the chloramines bond but also can leave high chlorine residual which must come back to normal levels before swimming is resumed. Recently the calculation for this has changed to account for the high chlorine level. Now we multiply the combined chlorine times 10 and then subtract the existing free chlorine reading. This end result is the amount of chlorine to be raised.
Recently there have been other options offered for chloramines removal. The use of a monopersulfate chemical which oxidizes the pool but does not leave a high residual of free chlorine is an accepted alternative. This is used on many “salt” or chlorine generation systems that do not have the ability of a boost cycle.
The use of ozone as a supplemental sanitizer has been shown to greatly reduce the amount of chloramines present in the water. Ozone does not leave a residual in the water but instead combines with the molecules to destroy or change them at point of contact. This contact point is before the sanitizer is added into the system. Therefore there is less waste to combine with the chlorine being addedafter oxidation. This in turn will create a lower chlorine demand for wastes before disinfecting the water. This is recommended also with chlorine generators to prolong the life of the cell.
UV light is effective in eliminating chloramines as it changes the molecules where they cannot reproduce and are then harmless. This method also does not leave a residual and is introduced to the pool water before the sanitizer is administered as in ozone.
Chloramines are the most important factor in pool water chemistry for the pool operator to be aware of and act upon. Eliminating wastes before entering the pool and regular testing of the water to determine chloramines levels are important to controlling the combined chlorine levels. Using a supplemental sanitizer to the system without raising the residual free chlorine would be preferable as many of these systems are more effective in treating chloramines and do not require a time of non swimming to let chlorine levels drop to an acceptable level. To be able to destroy chloramines on a continual basis with ozone or UV would allow for less sanitizer use and leave a safe friendly pool environment.