AUTHOR: EMEL KILIÇ –CHEMICAL ENGINEER ( HACETTEPE UNIVERSITY)
CHEMICAL DIVISION MANAGER – CAG KIMYA TURKEY
HEAVY METALS POLLUTION IN WATER
Generally the water pollution is described as the presence in water of enough harmful or objectionable material to damage the water's quality.
Water pollution has many sources and characteristics. Humans and other organisms produce bodily wastes which enter rivers, lakes, oceans and other surface waters; Industry is creating new chemicals each year, all of which eventually find their way to water. In high concentrations these wastes result in bacterial contamination and excessive nutrient loading (eutrophication). Inorganic industrial wastes are much tricker to control and potentially more hazardous Industries discharge a variety of toxic compounds and heavy metals, and wastewater from industrial process may also be too hot or too low in dissolved oxygen to support life.
First of all, we want to mention about the heavy metal sources which cause to water pollution.
Common Metals and their sources
- Lead: leaded gasoline, tire wear, lubricating oil and grease, bearing wear
- Zinc: tire wear, motor oil, grease, brake emissions, corrosion of galvanized parts
- Iron: auto body rust, engine parts
- Copper: bearing wear, engine parts, brake emissions
- Cadmium: tire wear, fuel burning, batteries
- Chromium: air conditioning coolants, engine parts, brake emissions
- Nickel: diesel fuel and gasoline, lubricating oil, brake emissions
- Aluminum: auto body corrosion
THE EFFECTS OF HEAVY METALS TO HUMAN HEALTH
Heavy metals are natural components of the Earth's crust. They cannot be degraded or destroyed. To a small extent they enter our bodies via food, drinking water and air. As trace elements, some heavy metals (e.g. copper, selenium, zinc) are essential to maintain the metabolism of the human body. However, at higher concentrations they can lead to poisoning. Heavy metal poisoning could result, for instance, from drinking-water contamination (e.g. lead pipes), high ambient air concentrations near emission sources.
Heavy metals are dangerous because they tend to bioaccumulate. Bioaccumulation means an increase in the concentration of a chemical in a biological organism over time, compared to the chemical's concentration in the environment. Compounds accumulate in living things any time they are taken up and stored faster than they are broken down (metabolized) or excreted.
Heavy metals can enter a water supply by industrial and consumer waste, or even from acidic rain breaking down soils and releasing heavy metals into streams, lakes, rivers, and groundwater.
Now we are going to describe the kinds of heavy metals, their dangerous levels and the effects of these heavy metals to human health and environment.
The most pollutans heavy metals are Lead, Cadmium, Copper, Chromium, Selenium and Mercury.
Lead In humans, Long term exposure can occur acute or chronic damage to the nervous system on humans.
Cadmium In humans, long-term exposure is associated with renal disfunction. High exposure can lead to obstructive lung disease and has been linked to lung cancer,and damage to human’s respiratory systems.
Copper is an essential substance to human life, but in high doses it can cause anemia, liver and kidney damage, and stomach and intestinal irritation.
Effect of the Mercury is to cause damage to the brain and the central nervous system.
Chromium is used in metal alloys and pigments for paints, cement, paper, rubber, and other materials. Low-level exposure can irritate the skin and cause ulceration. Long-term exposure can cause kidney and liver damage, and damage too circulatory and nerve tissue. Chromium often accumulates in aquatic life, adding to the danger of eating fish that may have been exposed to high levels of chromium.
Selenium causes to damage to circulatory tissue, and more severe damage to the nervous system.
Mercury causes damages to the brain and the central nervous system,causes psychological changes and makes development changes in young children. Normally Mercury is a toxic substance which has no known function in human biochemistry.
AN ALTERNATIVE TECHNIQUE TO REMOVE HEAVY METALS FROM WATER
The techniques of removing heavy metals from water are ordered as following,
On the other hand, one of the alternative techniques to remove the heavy metals from the water sources is BIOSORPTION.
Biosorption is a property of certain types of inactive, dead, microbial biomass to bind and concentrate heavy metals from even very dilute aqueous solutions. Microorganisms are used in biosorption. They take heavy metals into their cell surface or inside of bodies. That means microorganisms collect the heavy metals into inside.
Sources of Biomass for Biosorption
Biosorbents must be hard enough to withstand the application pressures, porous or “transparent” to metal ion sorbate species,
- Microorganisms (bacteria, fungi, yeast, molds)
- Activated sludge
- Fermentation waste
- Other specially propagated biomasses.
Organisms for Biosorption
There is a wide variety of microorganisms, including bacteria, fungi, yeast, and algae, that can interact with metals and radionuclides and transform them through several mechanisms
Examples of toxic heavy metals accumulating microorganisms
Organism * Element
Citrobacter sp. * Lead, Cadmium
Thiobacillus ferrooxidans * Silver
Bacillus cereus * Cadmium
Bacillus subtilis * Chromium
Pseudomonas aerugina * Uranium
Micrococcus luteus * Strontium
Rhisopus arrhizus * Mercury