Floating plastic media followed by hollow fiber microfiltration membrane was applied for surface water treatment. The performance of the system in terms of particle and microorganisms was investigated. The floating filter was examined at different filtration rates of 5, 10 and 15 m3/m2 x h. Treated water was then fed into a microfiltration unit where different filtration rates were examined at 0.6, 1.0 and 1.4 m3/m2 x d. It was found that polyaluminum chloride was the best coagulant for the removal of particle, algae and coliform bacteria. Average turbidity in treated water from the floating plastic media filter was 3.3, 12.2 and 15.5 NTU for raw water of 80 NTU and 12.9, 11.7 and 31.2 NTU for raw water of 160 NTU after 6 hours at the filtration rates of 5, 10 and 15 m3/m2 x h, respectively. The microfiltration unit could further reduce the turbidity to 0.2-0.5 NTU with low transmembrane pressure development of 0.3-3.7 kPa. Microfiltration membrane could retain most of algae and coliform bacteria remaining in the effluent from the pretreatment unit. It was found that at higher turbidity, algae and coliform bacteria removal efficiencies were achieved at lower filtration rate of the system of 5 m3/m2 x h whereas a higher filtration rate of 15 m3/m2 x h yielded better coliphage removal.
A B S T R A C TThe objective of this research was to study the possibility of using reclaimed municipal wastewater in cooling tower by treating the water using reverse osmosis (RO) membrane. In this study, RO membrane was operated at initial flow rate of 6.3 m 3 /d, whereas the initial transmembrane pressure (TMP) was at 116 psi. During the operating period, permeate flux slightly decreased to 4.8 m 3 /day with the increase of TMP up to 127 psi and membrane fouling resistance of 3.34E + 12 m −1 . Major membrane fouling mechanism was complete blocking followed by standard blocking and cake layer formation. Average permeate characteristics were 36.3 μS/cm of conductivity, 42.3 mg/L of TDS, 4.4 mg/L of hardness, 22.7 mg/L as CaCO 3 of alkalinity, 0.002 mg/L of iron, 0.05 mg/L as CaCO 3 , 1.5 mg/L of chloride, 2.1 mg/L of silica, and there was no phosphate passing through RO membrane. Percent rejections compared to UF treated wastewater were in the range of 90.2-99.9% except for silica where rejection was only 85.1%. Scaling and corrosion index was studied in terms of Langelier saturation index (LSI) and Ryznar stability index (RSI). Without RO membrane, LSI value was −0.59 and RSI value was 8.5. With RO membrane, LSI value was −5.0 and RSI value was 17.0. From calculation of cycles of blowdown, it was found that when using the membrane, the cycles increased from 2.3 to 44 cycles. This, then, resulted in reduction of makeup water from 379.0 to 221.2 m 3 /d, a decrease by 41.6%. Payback period of installation and operation of RO membrane system was 14 months.
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