Question

Discuss the importance of dissolved oxygen in water. What processes are generally responsible for the deoxygenation of the water?

Answer 1

Dissolved oxygen:

It is the dissolved amount of “gaseous oxygen” in the water. Oxygen enters water through direct atmospheric absorption, “rapid movement” or as a “waste product” of photosynthesis of the plants.

For many life forms, including fish, invertebrates, bacteria and plants, dissolved oxygen is necessary.  

These organisms use oxygen in their breath.

Deoxygenation of the water are responsible for the following process

Oxidation of organic\quad matter:

$C{ H }_{ 2 }O (aq)\quad +\quad { O }_{ 2 }(aq)\quad \xrightarrow [ Microorganisms ]{ \quad } \quad C{ O }_{ 2 }(g)\quad +\quad { H }_{ 2 }O\quad (l)$

Bio oxidation of the nitrogeneous matter:

${ NH }_{ 4 }^{ + }(aq)\quad +\quad 2{ O }_{ 2 }(aq)\quad \rightarrow \quad 2{ H }^{ + }(aq)\quad +\quad { NO }_{ 3 }^{ - }(aq)\quad +\quad { H }_{ 2 }O\quad (l)$

Oxidation of chemical reducing agent:

$4{ Fe }^{ 2+ }(aq)\quad +\quad { O }_{ 2 }(aq)\quad +\quad 10{ H }_{ 2 }O(l)\quad \rightarrow \quad 4Fe(OH{ ) }_{ 3 }(s)\quad +\quad 8{ H }^{ + }(aq)$

$2{ SO }_{ 3 }^{ 2- }(aq)\quad \quad +\quad { O }_{ 2 }(aq)\quad \rightarrow \quad 2S{ O }_{ 4 }^{ 2- }(aq)$

Answer 2

Dissolved oxygen:

It is the dissolved amount of “gaseous oxygen” in the water. Oxygen enters water through direct atmospheric absorption, “rapid movement” or as a “waste product” of photosynthesis of the plants.

For many life forms, including fish, invertebrates, bacteria and plants, dissolved oxygen is necessary.  

These organisms use oxygen in their breath.

Deoxygenation of the water are responsible for the following process

Oxidation of organic\quad matter:

C{ H }_{ 2 }O (aq)\quad +\quad { O }_{ 2 }(aq)\quad \xrightarrow [ Microorganisms ]{ \quad } \quad C{ O }_{ 2 }(g)\quad +\quad { H }_{ 2 }O\quad (l)