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12 - Starting Algoculture -
The site for the farm has been selected. The size and type of farm has been determined according to demand, climate, and local resources - water, power , chemicals, and financial possibilities.
Davougon Davougon photo :Technap
Pahou (Benin)
Madurai (India)
Madurai (India) photo: antenna.ch
The basins have been constructed. Paddlewheels are in place and motors connected. The strain of Spirulina has been chosen and grown in the laboratory, and we now have a monoalgal culture of at least 100 liters. We have decided on which culture medium to use - the least expensive and employing salts and chemicals available within the region. If the basin size is more than about 10 square meters, we'll "fence off"' with plastic, film, boards, or cement blocks an area of about half that size within the basin and install temporarily a submersible pump stirring system. The reason ? Remember, too much sunlight can destroy chlorophyll and kill the Spirulina. If we put only 100 liters of dense culture into a large basin the culture will become so diluted that the filaments will no longer shade and protect each other. We may have to put black netting or palm fronds over the basin until the culture becomes dense again. For most cases the first solution is prefered. For very large basins one must grow progressively larger cultures and then seed the big basin with at least as much culture as would be represented by a full culture basin of at least 1/5 the final surface area : 1 to 5, dense culture area to unseeded culture medium area. In addition, to prevent pH shock and too abrupt change of osmotic pressure, one must add the new culture medium in small increments over a period of, say, 12 hours. Of course, this will mean that the culture depth at first, when "opening up the flood gates" to increase the size of the basin, will be much less than when all the new nutrient medium has been added and the algae have acclimated themselves to the new pH and pressure. It is better to do this at night.
This is the simplest form of Artisanal Spirulina Production: Concrete floor, wood frame, and Plastic sheet

''CONCRETE BASEMENT for basin'' - Artisanal Production of Spirulina
Wood frame and concrete floor of artisanal basin

Broom stiring
Stirred by hand
or existing power line, with an electic motor,
photos: Claude Darcas
motorized stiring

photos: Claude Darcas
''Artisanal'' - ApproprIate technology  TOOL
Pully reduction drive for paddlewheel
The paddlewheels are started up to create turbulence, move the culture around the basin's "racetrack", and insure that the nutrients in the water are constantly available to all the algal filaments.
The water's temperature is checked twice a day; hourly if one has an automated system of probes and recorders. The same holds for pH readings. Temperature should not go over about 41°C nor under about 21°C during the daytime. When the temperature goes too high it can be controlled by covering the basin with black plastic greenhouse netting or by adding cooler water. The pH recommended is about 9.5 but in most cultures it runs around 10.0- 10.5. In the afternoons of days of strong photosynthesis the pH can rise to over 11.5. But nighttime respiration, converting carbohydrates into proteins, etc. ..and releasing CO² into the water brings the pH down again to 10.0 or 10.5 by morning.

Paddlewheels mix the water column very well for the first few meters downstream of the paddlewheel. .

Green House with Submerged pipes
But from there on, until the water reaches the paddlewheel again, the flow is laminar and the algal filaments which are on top have a tendency to stay on top and those on the bottom have a tendency to stay on the bottom. Only a slow "rolling over" effect caused by friction with the bottom of the basin and a similar effect seen at the sides of the basin succeed in continuing at a much slower rate the "in light-out of light" regime for the algal filaments. .. faster in shallow basins and slower in deep basins.
One can continue turbulence far downstream of the paddlewheel by putting baffles across the water channels so as to thrust the water upward, and then a little farther along the channel another baffle to push the water flow downward toward the bottom of the basin. Under poor meteorological conditions I obtained 36 grams of equivalent dry Spirulina per square meter per day.
The flat baffles I used were difficult to install and more fragile than desired, so I later used sand-filled PVC plastic pipe set across the channels and under water, alternatively near the surface and near the basin bottom.
deflectors action
This gave about the same effect, but any baffle system resists the flow of water and hence requires more power to be applied to the paddlewheels. Doubling or tripling the production certainly justifies using a little more "push " .
Another method of enhancing paddlewheel mixing is to put very low raised bars or ridges (herringbone pattern ) on the basin bottom. Water flowing over them will create vortexes that will mix the culture top-to-bottom.
A third way of imparting vertical mixing to horizontal flow is to make an imprinted pattern on the bottom material (whether it be of plastic or cement) where the imprint consists of an endless chain of long, fairly wide, oval grooves connected by venturi sections. A film of water will be sent toward the surface at the entrance to the venturi and downward into the groove after the venturi. The effect in trials at 10-cm per second was only partial, and interesting work remains to be done to maximize the effect and minimize clogging along the bottom pattern.

Concerning temperature at night: Spirulina is able to tolerate nighttime temperatures near freezing - they grow in Lake Titicaca at 12,506 feet (3800 meters) elevation. This actually is an advantage as there is less nighttime conversion of daytime carbohydrate photosynthate into excreted polysaccharides, so respiration biomass loss is minimized. But cold nights also can be a disadvantage as cold filaments are especially vulnerable to photolysis when flooded with bright and powerful sunlight at dawn. The advantage can be kept and the disadvantage eliminated if just before dawn the water can be heated to around 20°C and the mixing can be raised to maximum - that is, a turbulence sufficient to raise and lower the algal filaments rapidly in the water column - in and out of the sunlight. This way, maximum biomass is conserved and maximum photosynthesis can begin immediately. Otherwise there is very little photosynthesis until around 10:30 AM when the water has been sufficiently warmed naturally by sunlight ( and you have lost alI these hours of biomass production). As Spirulina is moderately thermophilic, temperature - up to 40°C - means greater yield. Low at night, high during the day but with maximum turbulence during the day is what is desired.

- Introduction ] CD-ROM Spirulina for Reducing Malnutrition - Historic of the World ]
- SPIRULINA Composition  ]   [  - Texcoco Lake Story  ]
 [ -  
WHERE SPIRULINA is found ] [  - Basins  ]   [  - Photosynthesis ]  
- SPIRULINA Production  ]  [  - Laboratory ]  [  - Harvesting ]
- Mix-drying SPIRULINA ]   [  - Starting ]  [ Problems and Solutions  ] 
[  -
- Why should we grow SPIRULINA ? : for nutrition and health ]
- Public Information-paper on SPIRULINAuseful links ]


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