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Origin of DO

There are two main ways in whichdissolved oxygen occurs naturally inwater: From the surrounding

atmosphere, where oxygen in the

surrounding air dissolves readilywhen mixed into water, up to

saturation, during water movements

Via photosynthesis when oxygen isproduced

b a uatic lants and al ae as a b -

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Importance

Accurate measurement of dissolvedoxygen is essential in processeswhere oxygen content affects

reaction rates, process efficiency orenvironmental conditions, such asbiological waste water treatment,

wine production, bio-reactions,environmental water testing.

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Factors effecting

DO in a solution is dependent on threefactors, namely

1. Water TemperatureSolubility of oxygen reduces as

temperature increases.

2.Salinity(Salinity is the saltiness ordissolved salt content)

The amount of dissolved oxygen

increases as salinity level decreases

http://en.wikipedia.org/wiki/Salthttp://en.wikipedia.org/wiki/Salt

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Galvanic Cell

The Galvanic Cell consists of twometals, the positive anode and the

negative cathode, connected by asalt bridge between the individual

half-cells.

As the metal electrodes leaveelectrons behind as they dissolve in theelectrolyte. The different properties of

the two metals causes them to dissolveat different rates hence a ressure is

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Polarographic Cell

The Polarographic Cell consists oftwo electrodes placed in theelectrolyte: One with fixed potential

called the reference electrode, andthe other with a variable potentialcalled the polarizable electrode.

As voltage is applied to thepolarizable electrode, a redoxreaction occurs, where electrons

break away from the electrode to

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Advantage of apolarographic cell

The cathode remains intact.

The current flow of the polarographic

cell is also linearly proportional to theamount of oxygen present in theelectrolyte, enabling the celltoprovide highly accurate

measurements at low oxygen levels.

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Applications1.Aquacultural: Use to monitor oxygen

levels in catfish and shrimp farming;game stocking ponds; ornamental fishtanks and ponds; and in other fishfarming applications.

2.Industrial: Ideal for checks on thequality of plant water intake anddischarge,wastewater and watertreatment, recirculating systems and

industrial process systems.3.Environmental: Use to test waterquality, monitor health of aquaticecosystems, survey surface and ground

water drinking supplies, and meet EPA