Heavy Metal Removal from Water
White Paper by Rami Elias Kremesti M.Sc., CSci, CEnv, CWEM
April 2, 2025
Kremesti Environmental Consulting Ltd –
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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/Coal Burning and Electroplating create waste water streams that are high in heavy metals like mercury, chromium, lead, cadmium etc 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. Roofers in the UK that use Lead sheets to cover and seal chimneys and valleys which can lead to hand-mouth contamination.
Various technologies are used for removing heavy metals from water.
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.
Historical Heavy Metal Contamination Cases
The Corby toxic waste case was a landmark 2009 legal battle in which Corby Borough Council in the UK was found liable for negligence that caused birth defects in local children. Often called “the British Erin Brockovich,” it was the first case in the world to legally establish a link between atmospheric (airborne) toxic waste and birth defects.
Between 1985 and 1999, the council undertook a massive reclamation project. This involved transporting millions of tonnes of industrial waste—containing heavy metals like cadmium, arsenic, and zinc—through populated areas in open lorries.
Historic heavy metal pollution cases show devastating impacts, from ancient lead poisoning in Roman workers and medieval wildlife to the infamous Minamata disease (caused by mercury) in Japan (1950s) and the Erin Brockovich case (hexavalent chromium) in California (1960s), highlighting how mining, gilding (like St. Isaac’s Cathedral), and industrial waste contaminated water and food, causing neurological damage, cancers, and mass deaths, with evidence found even in ancient bones and shells, proving long-term environmental harm.
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 (using OH- or S-2 ions), coagulation/flocculation, adsorption, phyto-remediation, evaporation 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.
Example: https://www.dupont.com/water/periodic-table/heavy-metals.html
2. Membrane Filtration:
Membrane filtration uses semi-permeable membranes to physically block the passage of heavy metal ions/colloids 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.
However, removing heavy metals at low concentrations with precipitation is inefficient because the resulting particles are too small to be easily separated and the chemical equilibrium requires adding high doses of precipitant, and some metals can re-dissolve if the pH is changed. Additionally, the presence of other substances like chelating agents can prevent precipitation, and in mixed metal waste, the optimal pH for each metal can differ, making it impractical to remove them all to low levels with a single 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/electrowinning process.
6. Adsorption
Using materials like chitosan-based adsorbents, activated carbon and Granular Ferric Oxide to bind and remove heavy metals from water. Bayoxide from Lanxess is one such material:
Greensand is a highly effective filtration media used for removing certain heavy metals and contaminants from water, primarily iron and manganese, as well as arsenic and radium. It works through a process of oxidation and filtration, often requiring chemical regeneration to maintain its effectiveness. Originally, Greensand got its name from the natural mineral clay glauconite which effectively removes/exchanges heavy metals from water and wastewater through adsorption/ion exchange, making it useful for water treatment, especially for metals like lead (Pb), zinc (Zn), cadmium (Cd), mercury (Hg), and copper (Cu), with high removal efficiencies often exceeding 90% and a capacity that can be enhanced through granulation or modification. Later, greensand started to be manufactured by fusing silica sand and coating it with a manganese dioxide coating.
The Inversand Company based in NJ, USA is widely recognized as a pioneering and historically most significant supplier, producing filter media for water treatment since 1925. They are generally considered the original and primary manufacturer and supplier of traditional manganese greensand, which is made from the naturally mined mineral glauconite.
Inversand invented the original Manganese Greensand product and later developed the enhanced Greensand Plus media. They have been a leader in the field for nearly a century, operating from their mine in New Jersey. For over 50 years, Inversand was effectively the only supplier of manganese greensand, with other competitive products appearing much later.
7. Capacitive De-Ionization CDI
Yes, capacitive deionization (CDI) can remove heavy metals from water. This technology uses an electrical potential difference between porous electrodes, often made of carbon materials, to adsorb and remove charged ions like heavy metals from contaminated water. Research has shown CDI is effective for removing various heavy metals, though removal efficiency can be influenced by factors like the type of metal, its concentration, and the presence of other ions.
8. AOP’s – Advanced Oxidation Processes:
Sometimes heavy metals are complexed or bound to complex organic molecules which makes removing them through ion exchange or chemical precipitation more challenging. In such cases, the organic part of the complex molecules might need to be oxidised using AOP’s.
Advanced Oxidation Processes (AOPs):
AOPs, such as Fenton, UV/Ozone or photocatalysis (e.g., using (TiO2), degrade the organic complexing agents (ligands) by generating highly reactive radicals (hydroxyl .OH radicals). This releases the heavy metal ions into the water in their free (ionic) form, which can then be removed using conventional downstream treatments like chemical precipitation or adsorption.
9. Phytoremediation
Phytoremediation uses plants to absorb heavy metals like lead (Pb), cadmium (Cd), arsenic (As), and chromium (Cr) from contaminated soil/water, with key examples including Indian Mustard (Brassica juncea), Brake Fern (Pteris vittata) for arsenic, Sunflower (Helianthus annus), Flax (Linum usitatissimum) for cadmium, and various aquatic plants/algae like Spirulina, Chlorella, and Water Hyacinth (Eichhornia crassipes) for a broad range of metals, utilizing mechanisms like phytoextraction to store metals in shoots or roots for later removal.
One time I was a train in Switzerland and over heard two scientists talking about how tobacco plants also bio-accumulate heavy metals and this is one of the reasons why tobacco smoke can contain toxic heavy mentals. Tobacco plants (Nicotiana tabacum) are excellent at removing heavy metals from soil through phytoremediation, and they efficiently absorb and accumulate metals like cadmium (Cd) and zinc (Zn) in their leaves, making them useful for cleaning contaminated sites, though this also creates hazardous plant waste.
10. Evaporation
Finally evaporating a heavy metal contaminated waste water allows us to recover pure water as condensate and this concentrates the heavy metals thus allowing less expensive disposal of the waste stream.
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.
Paques from the Netherlands.
Metal Recovery
Dutch Paques offers a metal recovery technology coupled with precipitation. The metal sulfide precipitation process of THIOTEQ™ Metal offers an attractive ROI at metal concentrations lower than 0.1g/l or 100 mg/l. Within three years, it made metal recovery at the Pueblo Viejo Mine profitable.
The Pueblo Viejo Mine processes 24,000 tons per day of polymetal ores containing gold, silver, copper and zinc. Since 2014, they have recovered up to 12,000 tons of high-grade copper per year and recycle up to 6,500 m3/h of process water after the neutralization plant with THIOTEQ™ Metal.
https://www.paquesglobal.com/applications/metal-recovery
https://www.paquesglobal.com/products/thioteq-metal
Health and Safety
he H&SE UK guidelines for working with heavy metals focus primarily on risk assessment, prevention of exposure, implementation of strict control measures, personal hygiene, and health surveillance. Compliance is managed through the Control of Substances Hazardous to Health (COSHH) Regulations and, specifically for lead, the Control of Lead at Work (CLAW) Regulations.
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.
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Rami Elias Kremesti Portrait