| Abstract | The goal of this research was to investigate the possibility of coupling CFMF with DAF
for algae separation. The investigation was done in two stages. The 1st stage of experiments,
which was used to study the behavior and to optimize the parameters effecting the two processes,
was conducted with a cultivated mono culture of algae with a concentration range of 50 to 350
mglL as the feed. In the 2nd stage, oxidation pond effluent containing multiculture algae with a
concentration range of 64 to 105 mg IL was used as feed to observe the real conditions. In the
first stage, the following parameters were examined: membrane size (0.2 to 5.0 µm), crossflow
velocity ( 1. 5 to 6. 0 ml s) and air injection mode and frequency, while with real wastewater,
crossflow velocity (2.0 to 5.5 mis), membrane pore size (0.2 to 2.0 µm), with and without
flocculent addition, were examined.
Results in stage I show that the permeate flux increases with increased crossflow velocity and
pressure, while pore size had a peak at 0.8 µm, where the flux was 583 higher than the other
sizes. At optimum CFMF conditions, the coupling of DAF showed no improvement in flux
without any pretreatment. The addition of alum, 350 mglL for mono culture and 650 to 850 for
oxidation pond water, showed a 2003 increment in stage I and 3003 in stage II, while coupling
with DAF further improved flux by another 803 and 240 to 260% respectively for the 0.2 µm
membrane.
The results for coupled DAF showed that the optimum permeate flux was obtained at 0.8 µm
membrane with a crossflow velocity of 3.5 mis. Increase in crossflow velocity showed a decrease
in flux while optimum DAF parameters obtained were with continuous air injection at a pressure
of 5. 0 bar. For oxidation pond water, increase in pore size showed a decreasing trend in
improvement of flux with coupled DAF (223, 29% and 233 for 0.8, 1.4 and 2.0 µm
respectively). Further, unlike in mono culture, where the removal was 65 to 70 3, with oxidation
pond wastewater the flotation process alone removed 90-95 % of the algae as a floated mat within
the 180 minuets of filtration. |