How to determine algae in given sample
Algae are common and normal inhabitants of surface waters. They differ from bacteria and fungi in that they have an internal green pigment called chlorophyll. Chlorophyll enables them, in the presence of sunlight, to combine water and carbon-di-oxide to form sugars or related substances with the release of oxygen by the process called photosynthesis. Recirculating cooling water systems normally are plagued with algae growth to a greater extent than once through systems. Heavy growths in spray ponds and cooling towers interfere with proper water distribution, preventing the desired cooling effect. Large masses of algae can also plug screens and restrict flow in pipelines and pumps.
Traditionally, algae have been classified on the basis of their color. Most important in cooling water are the green and blue green algae and the diatoms. Algae exist in a variety of shapes, but the most common are the single cell and thread like shapes. Algae may grow as free floating slime masses on the water surface, or they may attach to the walls of a cooling tower or reservoir. They exist at wide range of pH and temperature. Oscillatoria, chlorella, ulothrix and scenedesmus are some of the most commonly occuring genera of algae. Diatoms which are algae with silicates in the cell wall are also frequently encountered in the cooling water systems especially chromate treated ones.
Algae, being filamentous are difficult to enumerate. Visual observations and measurement of algal mat thickness, can help to determine the success of algal control to certain extent. Algal sensitivity towards biocides can be determined by treating algal sample in the presence of biocide and without biocide.
Equipment
Incubator
Autoclave
Photochamber assemble consisting of 2 fluoroscent tubelights fitted to a gas chamber.
Erlenmeyer flasks (250 ml capacity)
Algae culture broth
Pipettes
Dilution bottles
Spatulae
Procedure
1. Algae culture Broth is prepared by dissolving
1.0 gram Sodium Nitrate NaNO3
0.25 gram Dipotassium Hydrogen Phosphate K2HPO4
0.513 gram Magnesium Sulpate. Heptahydrate MgSO4 7H2O
50.0 mg Ammonium Chloride CaCl2
58.0 mg Calcium Chloride CaCl2
3.0 mg Ferric Chloride FeCl3 in 1000 ml. distilled water & pH adjusted to 6.8 to 7.2
2. Add 100 ml Algae culture medium in each 250 ml capacity flasks (40 Nos.)
3. Plug the flasks with non-absorbent cotton. Wrap the mouth of the flasks with paper / Aluminum foils.
4. Autoclave the flasks in an autoclave at 15 lbs pressure / inch2 at 121oC for 15 minutes
5. Cool the flasks to room temperature.
6. Collect wood scrapings from distribution strips or tower deck with the help of clean, spatulae (previously dipped in Alcohol) in a sterile petriplate.
7. Aseptically add few strands of algal sample or test water sample to the flask containing algae culture medium.
8. Incubate the flasks in a photochamber for 7 to 15 days. Put on the light at least 8 – 10 hours per day.
9. Presence of green, filamentous and / or uniform growth indicate presence of Algae in the test water sample.
10. Make wet mount of Algae culture developed from the test water sample over a microscopic slide and observe it under a compound microscope.
11. Note down the nature of Algae and identify the type of algae.
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