The effectiveness of different pretreatment on the fouling propensity of the feed was studied using synthetic waste water. The fouling potential of the feed was characterized by standard modified fouling index (MFI) and cross-flow sampler modified fouling index (CFS-MFI).In CFS-MFI, a cross-flow sampler was used to simulate the condition of a cross-flow filtration. The results indicated that the pretreatment such as flocculation with an optimum dose of 68 mg/l FeCl 3 substantially reduced the fouling propensity of the feed. The standard MFI of flocculated wastewater was reduced by around 99% compared to that of the untreated waste water. Similarly, the adsorption with powdered activated carbon (PAC) of 1 g/l reduced the standard MFI value to more than 99 % compared to that of the untreated waste water. The CFS-MFI values were lower than the standard MFI values for both treated and untreated waste water suggesting that the standard MFI was overestimated. The over estimation of the standard MFI compared to that of the CFS-MFI value was more than 99%.The effect of molecular weight distribution (MWD) of the foulants in the wastewater on the fouling propensity of the feed was investigated. The MWD was correlated with the MFI and CFS-MFI indices. It yielded useful insights in understanding the effect of MW on MFI and CFS-MFI and fouling propensity of the feed.

The removal of particulate matter and dissolved organic matter from seawater by the use of biofiltration was investigated. Granular activated carbon (GAC) and anthracite were used as bio filter media at two different filtration velocities. Filtrate quality was measured in terms of silt density index for seawater declined at a faster rate and continued even after 3 days when no pretreatment was provided.

A high rate fibre filter was used as a pre-treatment to seawater reverse osmosis (SWRO) to reduce membrane fouling. Seawater was drawn from Chowder Bay where the Sydney Institute of Marine Science, Australia is located. A lab-scale fibre filter with a height of 1000 mm and a diameter of 30 mm was used in conjunction with inline coagulation. The effect of operating the fibre filter with different packing densities (105, 115 kg/m 3) and filtration velocities (40, 60 m/h) was investigated in terms of silt density index (SDI 10), modified fouling index (MFI), pressure drop (ΔP), turbidity and molecular weight distribution (MWD). The use of in-line coagulation improved the performance of fibre filter as measured by the MFI and SDI. Regardless of filtration velocity and packing density the MFI and SDI 10 values remained low as did the turbidity until the end of the filtration run. The MWD analysis showed the removal efficiencies of organic materials like biopolymers, fulvic acids, low MW acids for even experiments with the highest filtration velocity (60 m/h) and lowest packing density (105 kg/m 3). This pre-treatment has a small foot print as it has the capacity of operating at a very high filtration velocity.

Hybrid processes combining fibre filter with deep bed filtration process such as (i) fibre filter and sand filter, (ii) fibre filter and anthracite and (iii) fibre filter and dual media filter were investigated as pre-treatments to SWRO. Seawater was drawn from Chowder Bay, Sydney. The effect of different pretreatment hybrid systems was investigated in terms of silt density index (SDI 10), modified fouling index (MFI), headloss across the filters and reduction in turbidity and dissolved organic carbon (DOC). The in-line flocculation in fibre filter improved the performance of the pretreatment hybrid system as measured by the MFI, SDI 10 , headloss, turbidity and DOC removal. The lowest SDI 10 and MFI were found with a fibre filter operated at a filtration velocity of 40 m/h followed by dual media filter operated at a filtration velocity of 5 m/h. The lowest headloss and turbidity was found with a fibre filter operated at a filtration velocity of 40 m/hr followed by anthracite operated at a filtration velocity of 5 m/h. This system also gave an effluent with the lowest DOC of 0.64 mg/L corresponding to a removal efficiency of about 70%.

In this study, different processes such as flocculation with ferric chloride (FeCl 3 ) and deep bed filtration (sand filtration and dual media filtration) as a pre-treatment to microfiltration (MF) were used for seawater desalination. The performance of these pre-treatments was determined in terms of silt density index (SDI) and modified fouling index (MFI) and flux decline in MF. Flux declin of MF with seawater was 45% without any pre-treatment, 42% after pre-treatment of FeCl 3 flocculation, 24% after pre-treatment of sand filtration with inline coagulation and 22% after pre-treatment of dual media filtration (sand and anthracite), respectively. MFI and SDI also indicated that deep bed filtration with in-line flocculation was better pre-treatment than flocculation alone. Detailed molecular weight distribution (MWD) of seawater organic matter was examined after different pretreatments. MWD of the initial seawater mainly ranged from 1510 Da to 130 Da. Deep bed filtration with in-line flocculation removed relatively large molecular weight of organic matter (1510 -1180 Da), while the small molecular weights (less than 530 Da) were not removed.