This study investigates the operation of dual media filter DMF during ambient and simulated algal bloom conditions, and the role of coagulation and dissolved air flotation (DAF) in mitigating the adverse effects of algal blooms on DMF performance. The study also highlights which AOM concentration as a function of biopolymer is critical to organic fouling in DMF pretreatment for Red Sea water desalination with RO. On the other hand, the present study has carried out another experiment on AOM fouling in comparison with bacterial organic matter (BOM) and humic organic matter (HOM) using two different pore sizes of UF ceramic membranes, 5 and 50 kDa. The main aim of this comparison is to examine fouling behavior and mechanism and removal efficiency. The study revealed that AOM can induce organic fouling in DMF during simulated algal bloom conditions at biopolymer concentrations as low as 0.2 mg C/L. DMF performance was strongly affected by AOM concentration as observed by flow rate decline through time. Liquid chromatography – organic carbon detection (LC-OCD) analysis showed higher removal rates of biopolymers than lower molecular weight fractions (i.e., humic substances, building blocks and low molecular weight neutrals) for all pretreatment scenarios. The study also indicated that while DMF performance was enhanced with coagulation and sedimentation, the most significant improvement in performance was observed for DMF operation preceded by coagulation and DAF. Hydraulic performance of DMF correlated well with biopolymers removal, with removal rates of 72%, 53% and 39%, for coagulation/DAF, coagulation/sedimentation, and no coagulation, respectively. For UF ceramic membranes, results showed that more TEP/organics were removed by the 5 kDa membranes compared to the 50 kDa membrane, which is accounted for lower MWCO. The UF 5 kDa membrane also showed low fouling formation than 50 kDa membrane for all of three types of organic matter tested. Analysis of the fouled membranes by SEM images showed that fouling was dominated by cake layer formation for the 5 kDa membrane while pore blockage followed by cake layer formation is apparent for the 50 kDa membrane.
|Date of Award
- Biological, Environmental Sciences and Engineering
|TorOve Leiknes (Supervisor)