การศึกษากระบวนการทำให้ลอยตัวด้วยอากาศที่ละลายน้ำเพื่อกำจัดสาหร่ายออกจากน้ำดิบ / พิษณุพล สงวนนวล = A study of dissolved air flotation process for algae removal from raw water / Pisanupon Sanguannual
This research is study on efficiency and optimum condition for algae removal from raw water by Dissolved Air Flotation (DAF) process. The study was done by using bench-scale DAF model and performed by spiking Chlorella species (unicellular green algae) with initial cell concentration of 10x10x10x10x10 cells/mL into tap water, and the other experiment was sampling water from pond containing high algae laden. Both of water types were investigated to find optimum recycle ratio and removal efficiency. For synthetic water, some variables that might affect DAF efficiency (pressure, initial feed concentration, turbidity, humic acid and sodium lauryl sulfate) and pre treatment by coagulation process were studied. The result of experiment indicated that optimum recycle ratio was about 10% and removal efficiency was 28.50% for synthetic water, higher performance was found with polishing pond water where the removal efficiency was about 42.24%. The variable parameters in this study showed that pressure change did obviously influence in DAF performance, higher pressure had the higher efficiency, but little change of efficiency could be seen when operated with higher pressure than 5 bars. The study also found that removal efficiency increased with initial feed concentration, and present of humic acid may be beneficial for DAF performance, while turbidity (not excess 130 NTU) and sodium lauryl sulfate did not affect on DAF. Pre treatment by coagulation was necessary to obtain high efficiency. Coagulant dosage and pH adjustment improved DAF performance. From the experiment operated with pressure of 5 bars, 10% recycle and 10x10x10x10x10 cells/mL of Chlorella as initial feed concentration, removal efficiency was only 28.5% without pre treatment, while the efficiency was 82.4% when used alum at optimum dose of 40 mg/L and adjusted to optimum pH as 7, in case of ferric chloride was used as coagulant, the optimum dose was 40 mg/L, pH as 5, the efficiency was 78%. While flocculation process with 5 minutes of flocculation time showed no improvement of removal efficiency