Countercurrent reverse osmosis process

Figure 1. Diagram of the Countercurrent Reverse-Osmosis Process...

We have demonstrated experimentally that the high osmotic pressure gradients associated with reverse-osmosis enrichment of ethanol can be reduced by adopting the process design of countercurrent reverse osmosis. However, the use of RO membranes in CCRO is limited at present by their inadequate selectivity and poor stability at high alcohol concentrations. 

In the next step, the filtered fermentation broth is contacted with an extracting solvent in a mbter-setder type of device (Section 6.4.1.2) the solvent extracts the antibiotic from the broth, aiong with many reiated and nonrelated compounds. Countercurrent extracting cascades in the form of centrifugal extractors are employed (Section 8.1.4, Figure 8.1.35) to reduce the contact/residence time. This process is often called product isolation in that the product has been isoiated from the broth however, the solvent extraction process extracts other compounds as well fram the broth. Often, adsorption (Section 7.1.1) as well as membrane processes such as ultrafiltration and reverse osmosis may be used (Sections 7.2.1.3 and 7.2-1.2). Sometimes, such a step results in a significant increase in product concentration. 

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