Porous resin airstone
Mili-bubbles are released from numerous pores of 150 µm of the airstone, and rise up in the water vigorously.
Fine bubbles of 100 to 500 µm are released from the porous ceramic plate, but go up toward the water surface rapidly.
Remarks: Micro-bubbles of less than 50 µm tend to have little buoyancy in the water, and stay there for a long time.
The salt water (salinity 31.2) was aerated with pure oxygen gas, using three different devices shown above, and the processes of dissolving oxygen gas to the water were compared. (Experimental conditions: 400 L of salt water, water temperature 23.4 to 27.8 ℃, gas flow rate 1.95 L/min.)
Porous resin airstone
The time required to reach 100 % dissolved oxygen (DO) saturation (about 7 mg/L) from
10 % DO saturation (about 0.7 mg/L) by the aeration of ambient air
|Device||Porous resin airstone||Micro-bubble diffuser||eco-Bubble®-400|
|Required time||About 60 min.||About six min.||About two min.|
|Dissolution rate of oxygen gas||1.7 %||16.4 %||52.7 %|
Remarks: The dissolution efficiency changes markedly depending on the conditions of aeration, in particular, viscosity
and depth of the water.
Larger amounts of micro-bubbles are produced in the water
with higher viscosity
eco-Bubble® with a nozzle of DDHRS type has an unique character as it can produce larger amounts of micro-bubbles in the water with higher viscosity, and exhibit higher capacity for dissolving gas to the water. Therefore, eco-Bubble® can dissolve oxygen gas to the water in the water more efficiently as the salinity of the water increases, releasing micro-bubbles.
Experimental conditions: 400 L of water, water temperature 8 to 12°C,
air flow rate 1.95 L/min.
Aeration with airstone
According to the general rule, the increase of DO of the water tends to be delayed as the salinity of the water increases.
Experiment: It took 12'22" to reach 50 % DO saturation from 20 % DO saturation in the freshwater with salinity 0. As the salinity of the water increases, the elevation of DO tends to be delayed. In the water with salinity 30, which is almost equivalent to sea water, about three times extended time (46'46") was required to reach 50 % DO saturation.
Aeration with eco-Bubble®: An opposite change of DO occurs in the water !
Experiment: It took 6'45" to reach 50 % DO saturation from 20 % DO saturation in the freshwater with salinity 0. As the salinity of the water increases, the elevation of DO tends to be accelerated inversely. In the water with salinity 30, the time required to reach 50 % DO saturation was reduced to half of the time in the freshwater, 3'44".
Note: The results of the experiment were based on those of the collaborated research with Dr. Hiroaki Tsutsumi,
Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto.