On the Removal of Alagl Bloom by Pressure Flotation

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Several experiments were conducted at Goryo Numa in Maebashi city in Gumma pref. where algal bloom were remarkable. As the results of these experiments showed that estimation was coincided well with it. However, experimental apparatus (flotation tank) which was used there was slightly large for experiment. Therefore, it took long time to replace the water in the flotation tank. Then it seems to me that some miss calculations might included into the experimental results. To avoid this miss calculation, the writer used small flotation tester. Experiment was conducted again for three kinds of coagulant using this flotation tester. These coagulants were just the same one in which the writer conducted experiments before. These were Al_2(SO_4)_3, PAC, Fe_2Cl_3. The amounts of coagulants used were 5-20mg/1. The water pressure to dissolve air into water was 3.5kgf/cm^2. Then the writer added this pressurized water to the water which contained algal bloom. Then the writer measured flotation velocity in the cylinder whose diameter was 5cm. The floatation velocity was 1.9cm/s at the good conditions. The flotation time of flock from bottom to surface is only 3 minutes when depth of tank is 3m. Consequently, 10 minutes of flotation times is enough to remove algal flock. As the results this experiments the writer thinks that flotation method is most suitable one to remove algae from irrigation water.