Membranes versus other Alternatives

Pilot studies of surface water treatment using membranes are reported very frequently in the literature. Many full scale applications also exist. With the increase in water quality regulations such installations are expected to become increasingly abundant (Jacangelo et al. (1997)). Levi et al (1997) described a satellite system, where water was treated locally using UF and NF. This avoided contamination by long distribution systems. 

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The purpose of the reference barrel is to allow for the simultaneous measurement of the cell membrane potential while measuring the intracellular ion activities with the ISE portion of the device. Tims, in practice, a second single-barrel reference micropipet electrode is placed in the bathing solution outside the cell so that the potential between the two KCl-filled electrodes can always be monitored to obtain the instantaneous cell membrane potential (E ). The potential of the liquid membrane ISE barrel can also be monitored versus the external reference electrode. In this manner, potential changes due to variations in the cell membrane potential can be taken into account when calculating the intracellular ion activities. Alternatively, only the potential difference between both barrels of the electrode could be monitored. This potential should only be dependent on the intracellular activity of the analyte ion (not affected by the cell membrane potential). For certain ion measurements, e.g., K using a valinomycin based liquid micropipet electrode, leakage of K+ from the reference barrel could present a problem. In such cases, the reference barrel and the outer reference pipet should be filled with a solution other than 3 M KCl. 

The conductivity of Naflon is higher than those of the sulfonated aromatic PEMs (4.2 mS/cm at 50% RH). The relative slopes of the log (conductivity) versus RH plots for each polymer are of interest and can illustrate the effect of humidity on each membrane s conductivity. The slope indicates the dependency of proton conductivity on the RH. Both Naflon and the multiblock copolymer exhibit similar slopes ( 0.026), and their slopes are lower than those of other random and alternating polymers, meaning that their conductivity is less dependent on the RH than those of the random and alternating polymers. To obtain more information on the difference in... 

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