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Heavy Metal Removal from Water

White Paper by Rami Elias Kremesti M.Sc., CSci, CEnv, CWEM

April 2, 2025

Kremesti Environmental Consulting Ltd

© 2025 – All Rights Reserved

 

Introduction

Sometimes heavy metals get into the drinking water supply from natural or anthropic sources and they need to be removed  because they are toxic. Other times, industrial processes like Iron/Lead Smelters, Mining, Biomass Burning and Electroplating create waste water streams that are high in heavy metals and these also need to be treated before safe discharge to the environment. I worked on a BECCS project in Sweden in which small amounts of heavy metals make it to the waste water through the process of pyrolysis of wood. Wood naturally contains trace amounts of various heavy metals like iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), lead (Pb), nickel (Ni), and cadmium (Cd), among others.

 

Toxicity

Heavy metal toxicity occurs when the body absorbs excessive amounts of certain metals, leading to various health problems, including organ damage and developmental issues, with common culprits being lead, mercury, arsenic, and cadmium. Manganese in drinking water supplies is toxic when inhaled in showers.

 

Heavy Metal Removal from Water

 

To remove heavy metals from water, you can use various water treatment technologies including ion exchange, membrane filtration (like reverse osmosis), chemical precipitation, coagulation/flocculation, adsorption and electrochemistry.

Here’s a more detailed explanation:

1. Ion Exchange:

 

This method involves using materials (like ion exchange resins) that selectively bind to and remove heavy metal ions from the water. Zeolites can also effectively remove various heavy metals, including lead, copper, cadmium, and zinc, from water. 
It’s a reversible process, meaning the resin can be regenerated for reuse.

Ion exchange is considered an effective end-of-pipe technique for heavy metal polluted wastewater treatment.

2. Membrane Filtration:

Membrane filtration uses semi-permeable membranes to physically block the passage of heavy metal ions and other contaminants.
Common types include ultrafiltration, nanofiltration, and reverse osmosis.
Reverse osmosis (RO) is particularly effective at removing a wide range of contaminants, including heavy metals. Note that heavy metals by their very nature will foul an RO membrane with time by forming scale on its surface or simply plugging the pores on the membrane. For a full review of RO water treatment technology, download our presentation.

 

3. Chemical Precipitation:

This involves adding chemicals such as NaOH and Sulfides to the water that cause heavy metals to form insoluble compounds (precipitates). Look at our presentation for precipitation of heavy metals using sodium hydroxide or sodium sulphide.
These precipitates can then be removed through sedimentation or filtration. Chemical precipitation is effective for removing heavy metals in low concentrations. The pH is a very important factor to consider in this step.

 

4. Coagulation and Flocculation:

Coagulation involves adding chemicals to neutralize the charge of colloidal particles, making them easier to clump together.
Flocculation then uses a “sticky” polymer to form larger, heavier particles (flocs) that can be easily removed by sedimentation or filtration.

5. Electrochemistry:

Electrochemistry uses electric currents to trigger chemical reactions that remove heavy metals.

Normally, a so called galvanic reduction reaction occurs at the Cathode where the heavy metals are selectively reduced/deposited as metals. This is the same principle as the electroplating process.

 

6. Adsorption

Using materials like chitosan-based adsorbents, activated carbon and Granular Ferric Oxide to bind and remove heavy metals from water.

 

Companies That Treat Heavy Metal Polluted Waters

Veolia – MetClean

P2W (Pollution to Water), an Israeli company, specializes in industrial wastewater treatment, particularly for the mining sector, focusing on technologies to treat contaminants like cyanides, heavy metals, and sulfates from gold, coal, and heavy metal mining operations.

 

 

About The Author

Rami Elias Kremesti is a chartered scientist specialising in water and waste water treatment based out of the UK. He worked on power station projects for over 10 years around the world. He is the published author of three philosophical books and enjoys cooking and spending time in nature and with his family.