Why Are Algaecides Necessary?

Transcription

1 Why Are Algaecides Necessary? Existing on the planet long before either plants or animals, algae form the basis of the kingdom Protista, a name that literally translates as "the very first". The kingdom can be subdivided into several phyla, covering everything from seaweed to slime moulds. The category even includes diatoms (golden algae of the phylum Chrysophyta); the glassy silicate shells of dead diatoms are ground down to prepare the diatomaceous earth that is often used in pool filters. Note that cyanobacteria, however, are often mistakenly referred to as "blue-green algae". Algae exist primarily in aquatic environments and, although not classified as plants, they do share plants' ability to use chlorophyll in photosynthesis. (1) The species of algae commonly encountered in swimming pools are usually identified by their colour; green, mustard and black. The latter is also referred to as "black spot" because of its propensity to form in large clumps or spots on pool surfaces. In contrast, "pink slime" is a generic term used to describe what may be a colony of methylobacteria, the exact identity of which is yet to be ascertained. Although pink slime is not due to algae, outbreaks can be treated effectively using a combination of Burn Out or Burn Out 35 and Back-Up. For further information, see TIB No. BG-027. Apart from the aesthetics of crystal clear, odour-free water, the presence of algae in pools can pose a health risk to swimmers. Direct contact has been related to outbreaks of a skin lesion known as protothecosis in susceptible individuals, whilst instances of gastrointestinal irritation accompanied by diarrhoea have also been reported. However, the greatest risk stems from the high chlorine demand that algal blooms impose upon pool water. This demand reduces the levels of free chlorine (or other sanitiser) in the water, allowing potentially harmful bacteria and amoebae to take hold. 1 / 8

2 Introducing MSA II Algaecide BioGuard MSA II is a patented, (2) highly concentrated algaecide powerful enough to kill all types of algae (excluding pink slime for the reason that it is bacterial, not algal, in origin), yet formulated to insure against instances of "green hair", water discolouration and pool surface staining so often encountered with copper-based algaecides. How does it do this? In traditional copper sulfate-based algaecides, copper (Cu2+) ions in the treated water are free to react with carbonates, hydroxides and other anions, leading to the precipitation of insoluble copper salts. These salts are responsible for scale and staining that may range in colour from bright blue through to black. However, by forming a stable polyacrylate complex with the metal, the copper in MSA II is prevented from reacting with these anions. The polyacrylate component is approved for use in food contact situations, and has been employed extensively in the sugar refining and food packaging industries. At the same time as the copper in MSA II is prevented from plating out, its algaecidal potency remains totally unaffected. Copper solutions make excellent algaecides as they kill a broader range of algae than is possible with polyquats. Even for those species of algae where polyquats are effective, copper often has a significantly better kill-rate. 2 / 8

3 In common with other copper-based algaecides, MSA II is believed to kill algae by either one or, possibly, both of the following mechanisms. In the first of these, copper ions combine with and deactivate essential cell enzymes, especially the -SH groups of enzymes. In the second, the copper disrupts the cell membrane of the algae, allowing the pool's sanitiser (eg. chlorine, bromine, etc.) to enter and kill the algae "from the inside". In both cases, it is essential that the pool remains well-sanitised for maximum kill efficiency. However, a word of warning. No matter what the algaecide used, if organic waste material is present in the pool, algae will be provided with nutrients vital to growth. Removing this food source by regular shocking using BioGuard Burn Out 35 or Lite is an essential part of a total algae prevention program. Specific Features and Benefits of MSA II Combating Potential Interactions After extensive testing by Bio-Lab's Technology and Development Department in the US, only one interaction of relevance to pool water was observed. This involved the presence of iron (Fe) in the treated water. It appears that the Fe3+ ion forms an even more stable complex with polyacrylate than does Cu 2+, so much so that the 3 / 8

4 iron may effectively "exchange" with copper in the complex and release free copper ions into the water. Investigations found that levels of iron in the range ppm were sufficient to liberate enough copper to give rise to cases of "green hair". Notably, few instances of scale were reported at these concentrations. Other metals, such as manganese and aluminium, had no discernible effect on the copper polyacrylate complex. The iron-copper exchange problem is obviously of concern to pool owners, particularly those who rely on saltchlorination as their means of sanitation. The reason? The commercial grade salt that is used in such units contains a number of trace metal contaminants, one of which is iron. Indeed, tests on pools in Australia suggest residual iron levels as high as 0.7 ppm are commonplace. Fortunately the solution is a simple one. Pre-treatment of the water with Scale Inhibitor in the case of a freshwater pool with pre-existing iron levels, or Salt Pool Stain & Scale Control in the case of a salt-chlorinated pool, effectively prevents the iron from plating out, staining pool surfaces or disrupting the copper polyacrylate complex in MSA II. The question that now might be framing itself in the minds of potential customers is, "If I need to add Scale Inhibitor or Salt Pool Stain & Scale Control before I can use MSA II, why don't I just revert to my cheaper copperbased algaecide?" The answer is, "You can, but only if you want to use at least twice as much Scale Inhibitor or Salt Pool Stain & Scale Control to minimise the chances of scale forming in your pool." 4 / 8

5 Why? Quite simply, all of the copper in these cheap algaecidal alternatives is present as free copper ions. To avoid problems with "green hair" and scale, this copper - in addition to any pre-existing metals (particularly copper and iron) from other sources - has to either be bound up or removed completely. The real risk here is that binding or removing the copper associated with the algaecide itself will dramatically reduce its ability to kill algae. MSA II suffers no such drawbacks, since the copper loses none of its algaecidal potency by its being bound up in a polyacrylate complex. In addition, the complex is stabilised against decomposition and the removal of copper by Scale Inhibitor or Salt Pool Stain & Scale Control. Benefits of Using MSA II with Quick Clear If Scale Inhibitor or Salt Pool Stain & Scale Control is used, and is supported by the addition of Quick Clear to the pool's filter, several additional benefits arise: - Apart from unsightly rust stains and discoloured water, the presence of iron can damage pool surfaces, sometimes irreparably. - Any free copper that may be present in the pool from sources such as corroding heat exchangers is removed. - Excess calcium is removed from the water, thus reducing the possibility of scale (in the form of calcium carbonate) on pool surfaces. - Other metals with the potential to affect water clarity, such as manganese and aluminium, are also removed. - Salt cells and filter units are kept free of metallic deposits, thereby improving chlorination and filtration efficiency, respectively. With the combination of MSA II, Scale Inhibitor or Salt Pool Stain & Scale Control, and Quick Clear, the pool owner has the complete treatment and maintenance program for controlling both 5 / 8

6 algae and metals. Initial and Routine Maintenance in Pools Initial Dosage: 50 ml of MSA II per 10,000 litres. Monthly Winterising Maintenance Dosage: 40 ml of MSA II per 10,000 litres. Procedure: 1. If pool water tests positive for iron, pretreat with Scale Inhibitor for freshwater pools, or Salt Pool Stain & Scale Control for salt-chlorinated pools, as per directions. Allow at least 1 hour prior to treating water with MSA II. 2. Optional: To remove metals completely from pool water, add Quick Clear to pool filter as per directions. If this step is included, MSA II should not be added to the water until tests show zero levels of metals. 3. With pump and filter running, dilute recommended dosage of MSA II in at least 5 litres of water, then pour around edges of pool. 4. Allow water to circulate for at least 1 hour following application. Treatment of Existing Algae in Pools 6 / 8

7 Dosage: 100 ml of MSA II per 10,000 litres. Procedure: 1. Vacuum visible algae to waste and remove all leaves and other foreign material. 2. Brush all pool surfaces thoroughly. 3. With filter running, add Burn Out 35 as per directions to eliminate organic matter that might serve as nutrients for algal growth. 4. Allow water to circulate for at least 1 hour. 5. If pool water tests positive for iron, pretreat with Scale Inhibitor for freshwater pools, or Salt Pool Stain & Scale Control for salt-chlorinated pools, as per directions. Allow at least 1 hour prior to treating water with MSA II. 6. Optional: To remove metals completely from pool water, add Quick Clear to pool filter as per directions. If this step is included, MSA II should not be added to the water until tests show zero levels of metals. 7. Allow at least 1 hour prior to treating water with MSA II. 8. Dilute dosage of MSA II in at least 5 litres of water, then pour around edges of pool. 9. Repeat Burn Out 35 treatment after 4 days if some algae remains. 7 / 8

8 10. Vacuum dead algae to waste. To prevent any recurrence of algae, it is vitally important that all pool items (maintenance equipment, toys, etc.) are placed in the pool at the time of the MSA II treatment. Clothing (swimwear, towels, etc.) that might have come into contact with the algae should be washed thoroughly to prevent re-contamination. References 1. J.W. Kimball, "Biology", 4th edition, Addison Wesley Publishing Co., Reading MA, 1978, pp J.P. Garris, US Patent 5,541,150 (Dated 30 July, 1996). The above information is supplied by Bio-Lab and represents its best interpretation of available technical information at the time of preparation. The sole purpose is to supply factual information to Bio-Lab customers. It is not to be taken out of context nor used as support for any other claim not made herein. 8 / 8