FILTRATION PROTOCOL

Parameters of interest are solution pFl, ionic strength, calcium concentration, primarj colloid size (75, 250, and 500 nm), organic type and concentration, as well as membrane type and hydrophobicity, aggregate structure, and colloid stability. 

Initially the membrane was tested with organics and model primary particles in order to establish a baseline. As the chapter proceeds the systems become more and more complex and approach the properties of a real surface water. The success of this can be observed in the similarity of the membrane deposit for a surface water and the synthetic mixture. 

Pure water flux was determined for each membrane using 3 L MilliQ water. The last 100 mL of filtrate were analysed for TOC as a control sample for organic contamination. The cell was then filled with the feed solution, the stirring switched to 270 rpm, and the pressure adjusted to 100 kPa (unless indicated otherwise). Two types of filtration protocols were used, a standard and a regck protocol. Pure water flux was determined after the recycle experiments only, using 1 L of MilliQ water. 

For standard experiments samples were taken from the feed solution, three subsequent permeate solutions (270 mL each), and the concentrate (sampled using a pipette in order to avoid disturbance of the deposit on the membrane). About 1 L of feed solution was filtered per experiment. The equipment was further flushed with MilliQ water after the membrane was removed. 

For regcle experiments, the above procedure was repeated three times. The permeate was collected, sampled and filtered another two times without redispersion of the cake. Samples were taken during each recycle step and the total feed volume was about 1.5 L. Membrane flux averaged over an interval of filtration was calculated as 

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While this method is commonly used (De Nobih and Fornasier (1994), Kiichler et al. (1994), Mazid (1988), BeUn et al. (1993), Shaw et al (1994), Burba et al (1998), Buffle et al (1978), Crum et al (1996), Aiken (1984), Amy et al (1987), Reinhard (1984), Amy et al (1992), Hepplewhite (1995)), most authors have used different filtration protocols for their fractionation experiments. Cells can be operated in series (cascade) or in parallel, volumes and concentrations are varied, and some authors refill the cell with pure water to keep the cell concentration constant. All these factors influence the results obtained, and solution chemistry, pH, and ionic strength may also influence results. Generally reported size results are above the expected sizes of FA and FIA. UF MWCOs used are usually 0.5-1, 3, 5, 10, 30 kDa. 

Filtration protocols are described in the relevant chapters, microfiltration, ultrafiltration and nanofiltration, respectively. Membrane characteristics such as suifiace charge and morphology are also presented in these chapters. 

For fractionation experiments, the perspex stirred cells (see Chapter 4 for equipment description) were operated directly from the nitrogen bottle without a reservoir. Membranes were floated in a beaker of MilliQ water, skin side down, for at least one hour to remove the glycerin coating. Then at least 300mL of MilliQ water were filtered through the membrane. The filtrate was analysed with UV and DOC to confirm full removal of glycerin. The membranes were reused up to 5 times and stored in 0.1 % sodium azide at 4 C. Pure water flux was measured after the filtration of 500 mM of MiUiQ water prior to each experiment. The filtration protocols for serial and parallel fractionation were described in Chapter 4. In this Chapter parallel fractionation results will be shown. 

Two filtration protocols were used for fouling experiments, one for the 10 kDa membrane and another for the 100 kDa membrane. The different fluxes did not allow the filtration of similar volumes. 

Two membranes were examined, the 10 kDa (PLGC) and the 100 kDa (PLHK). Pure water fluxes and filtration protocols were described earlier in this chapter. The flux ratios shown in this section are the fluxes over the initial flux at the start of the experiment (not pure water flux). This compensates for any initial osmotic effects of the feed solutions. 

Table 8.3 F/ux, flux decline, permeability, membrane resistance and rejection at 2.5 mM CaCl2 and IHSS HA at pH 7-8. Filtration protocols are described in Chapters 5,6 and 7 forMF, UF, and NF, respectively.

Specifically, it is suggested that a filterability evaluation be used as an added criteria to supplement viscosity to assure polymer hydration. Whereas the use of the API procedure is applicable in some oil field applications even more demanding filtration protocols may be appropriate. Similarly particle suspension considerations were used to define polymer solution functionality. It is of utmost importance to define the basic purpose of using water soluble polymers and to devise tests to assure that the polymer solutions selected be evaluated with those specific purposes in mind. 

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