Fouling-release potential

A potential solution to prevent fouling is to develop fouling release membranes that do not resist the adhesion of foulants, but have an active layer with a low surface energy so that adhered foulants can be readily washed away by hydrodynamic mixing in the membrane module [21] provided the water flux and salt rejection of the resulting membrane are not compromised. 

Typically, the electrodes are of lead dioxide on a titanium substrate in the form of horizontal perforated plates, usually 5-40 mm apart, depending on the conductivity of the liquid. A potential difference of 5-10 V may be applied to give current densities of the order of 100 A/m2. Frequently, the conductivity of the suspension itself is adequate, though it may be necessary to add ionic materials, such as sodium chloride or sulphuric acid. Electrode fouling can usually be prevented by periodically reversing the polarity of the electrodes. Occasionally, consumable iron or aluminium anodes may be used because the ions released into the suspension may then assist flocculation of the suspended solids. 

The manual operation of water jets for on-line cleaning has been used for the removal of fouling deposits for many years, although modern soot blowing equipment is often preferred. Similarly shot cleaning, which involves the release of metal shot so that as it falls under the influence of gravity, it impacts the heat-transfer surface and removes any accumulated deposits. The technique is not widespread on account of the potential damage that could occur. 

Many flowering plants attract insect pollinators by releasing odorant molecules that mimic an insect s natural food sources or potential egg-laying sites. Plants pollinated by flies or beetles that normally feed on or lay their eggs in dung or carrion sometimes use foul-smeUing compounds to attract these insects. 

In general, it may be concluded that despite the endeavor described earlier to develop low-fouling membranes via surface modification with nanoparticles, further research is still needed to investigate the combined effects of the water chanistry, the nature of the nanoparticles, and the coating conditions on the modified-manbrane performance and fouling mitigation. Also, careful control and monitoring of the nanoparticles released from the modified membranes are necessary to minimize potential environment (eco) toxicity effects (Tiede et al. 2009). 

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