Chemistry behind thermal pollution

Anand R Founder, Evolvingminds

&Utkarsh Sethia

Intern, Evolvingminds

14th Jan , 2017

A picture is worth a thousand words

Reference - http://www.crystal-lagoons.com/

Hot water is less dense than cold water

Reference - http://www.learnz.org.nz/

Saltwater is more dense than freshwater

Reference - www.science-sparks.com , http://bucketlistjourney.net/ , https://www.zigzagonearth.com/

Reference - http://www.evolvingminds.org/ , https://www.youtube.com/user/FlinnScientific

Gases are less soluble in hot water

Reference - http://fphoto.photoshelter.com/ https://basofscience.files.wordpress.comBook – Introductory Chemistry, 4th edition by Nivaldo J. Tro

Warm soda pop fizzes more than cold soda pop because the solubility of the dissolved carbon dioxide decreases with increasing temperature

Reference - http://straighttothehipsbaby.blogspot.in/Book – Introductory Chemistry, 4th edition by Nivaldo J. Tro

Sometimes bubbles begin to form in hot water below 100 degree Celsius. These bubbles are dissolved air – not gaseous water – leaving the liquid

Reference - https://commons.wikimedia.org http://www.poolspas.ca/ , www.chemtreat.com Book – Chemistry, 7th edition by Zumdahl

Boiler scale is a deposit that forms directly on heat transfer surfaces. Bicarbonate ion is formed when carbon dioxide is dissolved in water containing the carbonate ion

Hard water contains calcium ion Calcium bicarbonate is soluble in water, but calcium

carbonate is insoluble. When the water is heated, the carbon dioxide is driven off.

For the system to replace the lost carbon dioxide, the reverse reaction must occur

This reaction, however, also increases the carbonate ions, causing solid calcium carbonate to form.

This solid is the boiler scale that coats the walls of containers such as industrial boilers and tea kettles.

Boiler scale reduces the efficiency of heat transfer and can lead to blockage of pipes.

Reference – Book (Chemistry, 7th edition by Zumdahl)

Thermal imagery

Reference - http://www.eurosense.com/

Thermal pollution explained• Water from lakes and rivers is used for industrial cooling.• After being used, the water is returned to its natural source

at a higher than ambient temperature.• Because it is warmer, this water contains less concentration

of oxygen and is also less dense.• It tends to float on the colder water below, thus blocking

normal oxygen absorption.• This effect can be especially important in deep lakes.• The warm upper layer can seriously decrease the amount

of oxygen available to aquatic life in the deeper layers of the lake.

Reference – Book (Chemistry, 7th edition by Zumdahl)

Reference - https://www.satelytics.com/

The metabolic rates of fish and other aquatic animals increase in the warmer water released near the plant outlet; thus, their need for oxygen increases. But the concentration of dissolved oxygen is lower at the higher temperature. This oxygen depletion can harm these aquatic populations.

Reference – Book (Chemistry , The molecular nature of matter and change by Martin S. Silberberg)

Sustainable industrial cooling

Reference - http://www.crystal-lagoons.com/

Thank you

Evolvingminds – anand@evolvingminds.org , +91 99452 75572 Utkarsh Sethia – sethiautkarsh@gmail.com , +91 80562 70110