environmental microbiology

1. Methods for Removal of Dissolved Solids from
Water
Dr. Devendra Mohan
Professor and Former Head
Department of Civil Engineering
Indian Institute of Technology (Banaras Hindu University)
Varanasi – 221005

2. Distillation
• Process of separating components of a liquid mixture through selective
evaporation and condensation

3. Solar Distillation
• Process to use solar energy to
purify water through
evaporation and condensation

4. Chemical Precipitation
• Process of converting a soluble substance into an insoluble form by
adding chemicals to it
• Applications of chemical precipitation include:
1. Water Treatment
2. Metal Extraction
3. Chemical Analysis

6. Adsorption
• Adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to
surface
• Surface Phenomena
• Adsorbate-ions, atoms, or particles that adhere to surface of adsorbent
• Adsorbent- material that has the ability to attract and hold molecules of a gas,
liquid, or dissolved substance on its surface

8. Adsorption Vs Absorption

9. Ion Exchange
• Exchange of ions of the same charge between an insoluble solid and a
solution in contact with it
• Used in water-softening and other purification and separation processes

11. Electrodialysis
• Water treatment process that uses an electric field to move ions through
semipermeable membranes from one solution to another
• Applications:
1. Desalination
2. Drinking water production
3. Food processing

13. Microfiltration
•Removes large particles like suspended solids, bacteria, and
some viruses
•Does not remove dissolved substances like salts or small
molecules
• Applications:
1. Clarification of liquids like beverages.
2. Wastewater treatment (removing bacteria and suspended solids).
3. Pre-treatment for other processes like ultrafiltration or reverse
osmosis.

15. Ultrafiltration
•Removes larger molecules such as proteins, colloids, and viruses, as well as
bacteria
•Still allows small molecules like salts, sugars, and smaller organic compounds to
pass through
•Applications:
1. Protein separation in biotechnology and pharmaceuticals.
2. Water purification (removing pathogens).
3. Pretreatment for nanofiltration or reverse osmosis.

17. Nanofiltration
•Removes multivalent ions, small organic molecules, and some dissolved salts
•Allows monovalent ions like sodium (Na⁺) and chloride (Cl⁻) to pass through but with
partial rejection
•Applications:
1. Softening water by removing divalent ions like calcium and magnesium
2. Removing color, pesticides, and organic compounds from water
3. Separation processes in food and beverage industries

19. Reverse Osmosis
•Removes almost all dissolved salts, ions, and small molecules,
including monovalent ions like Na⁺ and Cl⁻, as well as organic
compounds
•Capable of producing near-pure water by removing dissolved solids,
bacteria, viruses, and chemicals
•Applications:
1. Desalination of seawater or brackish water
2. Purification of drinking water
3. Industrial water treatment and wastewater recycling
4. Pharmaceutical production and food processing

26. CDI (Capacitive Deionization)
• Electrochemical water treatment process used to remove dissolved
ions from water
• How CDI Works:
1. Ion Migration
2. Electrostatic Adsorption
3. Water Purification
4. Regeneration

28. Nalgonda Technique
• Removal of fluoride from water
• Chemicals used in the Nalgonda technique are alum (aluminum sulfate),
lime (calcium oxide), and bleaching powder

30. Prashanti Technique
• Water treatment method that uses activated alumina to remove fluoride
from water
• Can be used for both community and domestic defluoridation

31. AMRIT
• AMRIT stands for Arsenic and Metal Removal by Indian Technology
• Technology utilizes nano-scale iron oxy-hydroxide, which selectively
removes arsenic when water passes through it
• AMRIT is applicable for both domestic and community-level water
purification

34. Arsiron Nilogon
• Iron-based coagulant specifically designed for the removal of
arsenic from water
• Found effective for both As(III) and As(V) forms of arsenic
• Performance depend on factors such as pH, concentration of
arsenic, and the presence of other ions

35. Arsiron Nilogon

36. Sono filter
• Water filtration system designed to remove arsenic from drinking water
• Filter uses a composite iron matrix, river sand, wood charcoal, and brick
chips to remove up to 98% of arsenic and other contaminants

38. SORAS
• SORAS stands for Solar Oxidation and Removal of Arsenic
• Process uses solar energy to oxidize arsenic in contaminated water for
removal of arsenic
• Benefits of SORAS :
1. Low-cost
2. Environmentally Friendly
3. Easy to implement in rural areas

40. Sand coated with iron
• Used for removing arsenic from water
• In this method, a thin layer of iron is coated onto sand particles, which
enhances the adsorption of arsenic when water passes through the filter

41. Sand coated with manganese
• Used for removing arsenic from water
• Manganese dioxide coating enhances the ability of the sand to adsorb
arsenic, especially arsenic (III) and arsenic (V), through an oxidation-
adsorption process.