Chai Hoon Koo

Use and Development of Fouling Index in Predicting Membrane Fouling

Abstract Membrane fouling has been recognized as an inevitable problem impairing all membrane processes. Fouling control strategies have been adopted to resolve membrane fouling. Fouling index is one of the most popular fouling prediction tools used to predict the fouling potential of feed water in membrane filtration systems. This paper provides an overview of the past and present developments of fouling indices measurement techniques as the membrane fouling prediction tool in reverse osmosis/nanofiltration process. This paper also addresses the possible fouling mechanisms and type of fouling in water filtration processes, start-of-art techniques used to assess fouling mechanisms and methods to predict fouling. The fouling prediction methods highlighted are silt density index (SDI) and modified fouling index (MFI). These fouling indices are correlated with their applications in evaluating the pretreatment efficiency and the flux decline predictions of a feed. Even though there are a number of researchers focusing on the measurement of MFI, the MFI obtained was not correlated to the quality of feed empirically. An appropriate index should be capable of being used as an input to mathematical models for predicting the degree of fouling in a discrete form. The future direction and potential use of fouling indices are also discussed.

Comparative Assessment of Membrane Fouling Propensity Using Colloidal Silica as Foulant

Other than silt density index (SDI), modified fouling index (MFI) is claimed as one of most useful fouling predictive tools in the practice of reverse osmosis. In this study, the effect of colloidal silica particles on the MFI value with the presence of crossflow sampler (CFS) cell at the upstream of MFI setup was systematically investigated. Colloidal silica with the particle size ranging from 70-100 nm was used as the model foulant in this experiment. The feed silica suspension was 0, 50, and 200 mg/L. The effect of membrane pore size as the test membrane in the dead-end cell on the fouling indices was also studied. Polyvinylidene fluoride (PVDF) membranes with molecular weight cut-offs of 150 and 100 kDa were employed. As predicted, the experiment results demonstrated that the fouling indices increased significantly as the feed silica concentration increased. The CFS-MFI values were always lower than the MFI in all the fouling index tests due to the shear force effect generated under the crossflow filtration mode. The fouling index generated from PVDF100 was higher than that of PVDF150 due to the retention of smaller particles. For this reason, PVDF100 membrane was preferred to be used as the test membrane for fouling index tests using colloidal silica over the PVDF150.

Pilot study for sewage wastewater reclamation and reuse using RO membrane: comparison of different pre-treatment systems

AbstractA pilot plant study was designed to monitor the performance of two parallel lines with a capacity of 50 m3/day using different pre-treatment technologies prior to reverse osmosis (RO) units for water reclamation from a local-based effluent treatment plant in Malaysia. Line 1 consisted of coagulation-pore controllable fiber filter (PCF) and was denoted as PCF-RO, while line 2 was sand filter-ultrafiltration (UF) and was denoted as UF-RO. The pilot plant was operated continuously everyday for three months throughout the study. In the PCF-RO line, ferric chloride was chosen as a coagulant for the system. The performance and efficiency of PCF-RO compared to UF-RO in terms of system operability, percentage reduction of parameter tested, system deterioration, and the effectiveness of ferric chloride as coagulant were investigated. The results showed that permeate quality for both systems met the WHO drinking water standard for drinking water. However, membrane performance for PCF-RO which was deteriorat...