The Water Treatment Process

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Water treatment process overview

The first step in creating a cyanobacteria-directed biodesalination apparatus is selecting a species that possesses proper metabolic and morphologic characteristics. The organism must then be genetically modified to optimize ion regulation, and light regulation of the desalination process. Cyanobacteria use photosynthesis for removal of sodium from the intracellular matrix of the bacterium. Through regulation and genetically modifying the bacteria to express halorhodopsin (Hr) this photosynthetic system can be harnessed to import chloride ions. This process creates an electrochemical gradient to drive sodium influx.L1 The selected strains of cyanobacteria do not endogenously contain the rhodopsin and all-trans-retinal complex. However, a desired cyanobacteria strain may integrate foreign DNA from other bacteria cell lines, such as Natronomonas pharaonis, that encodes for the Hr protein.L3,L2 Functionality of Hr protein also depends on the expression of the chromophore all-trans-retinal which is derived from carotenoids.L6 Many carotenoids have been defined in cyanobacteria, however, these must be converted to all-trans-retinall.L4, L5

Photosynthetic cyanobacteria export sodium via active transport from ATPases, or a proton coupled antiporter.L6,L7 Through this method, an initial low salt environment is created within the bacterium itself. Sodium expulsion is ATP dependent and halts when the ATP stores of the bacterium are depleted.L6 Halting the production of ATP can be accomplished in multiple ways, but one of the easiest to control and economically efficient would be to remove light wavelengths required for ATP production.L6 Once ATP reserves are depleted, active sodium export is stopped and ...

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...ually or even more adept. In addition, applying this process on an industrialized scale will be quite the challenge. Finding the ideal ratio of culture size to seawater volume to extract all of the salt in addition to maximizing economic efficacy will be imperative for successful implementation. There are many obstacles to applying proper genetic manipulation with the cyanobacteria. The expression of Hr is naturally found in salt-tolerant archaea species, but is not known to be endogenous to cyanobacteria. While versions of this protein have been successfully expressed in E. Coli and mammalian cells1, more research needs to demonstrate that this procedure can be attained with the suggested species of cyanobacteria. Moreover, it is not known how much NaCl can enter the bacteria before some sort of cellular destruction occurs and renders the entire process unworkable.
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