university of Agriculture
Definition of Heavy Metals
• Heavy metals are those metal of relatively high
density, or high relative atomic weight.
• Heavy metal can include elements lighter than
carbon and can exclude some of the heaviest
• It mainly includes:
- Some metalloids
COMMON HEAVY METALS CAUSING
Zinc and Copper
Sources of heavy metals pollution
• Primary sources of heavy metals are point sources:
- Coal-burning power plants
- Diffuse sources (combustion by-products
and vehicle emissions)
• Waste-derived fuels are especially prone to contain heavy
metals, so heavy metals are a concern in consideration of
waste as fuel.
• Electronic waste is also a significant source of heavy metal
Aluminium aqueous pollution
The amount of aluminium in seawater is
0.013 and 5 ppb. River water generally
contains about 400 ppb of aluminum.
• Regular aluminium concentration is 0.4ppm
• Below pH 4.5 solubility increases and
concentration becomes upto 5ppm and so its
pollution level is also increased.
Arsenic water pollution
• Arsenic contamination of groundwater is often due to naturally
occurring high concentrations of arsenic in deeper levels of ground
• Its sources are geochemical processes, mining activities
• Industrial and manufacturing processes.
• through the dissolution of minerals and ores, and as a result of
erosion from local rocks.
• It can causes:
• Irritation of the stomach and intestines
• Red and white blood cells decreased production, skin changes and
Antimony aqueous pollution
• Major sources of antimony in drinking water is waste water from
petroleum refineries; fire retardants; ceramics; electronics.
• It causes lung irritation, heart and lung damage, stomach pains,
diarrhea, vomiting and stomach ulcers.
• Its elevated level adversely affect the plant growth.
• Cadmium aqueous pollution:
• Maximum contaminant level for cadmium is 0.005 mg/L or 5 ppb.
• Cadmium applications- including electroplating and the manufacture
• Contaminated foodstuffs can result in emphysema, renal failure,
cardiovascular disease, and perhaps cancer.
Lead aqueous pollution
• Action Level for Treatment Technique
in parts per million (ppm)
Lead = 0.015 ppm
• Health Effects
Infants and children: Delays in physical or mental
development; children could show slight deficits in attention
span and learning abilities.
Adults: Kidney problems; high blood pressure
• Sources of contamination
Corrosion of household plumbing systems, erosion of natural
deposits. Industrial sources such as lead mining, smelting and
coal combustion, the use of lead-based paint and lead
containing pipes in water supply systems.
Quality Standard for Groundwater
Categories of Ground
• Category 1 and 2 reflects the low contents of chemical components
• Category 3 reflects that it is applicable to concentrative drinking
water sources and industrial and agricultural water use.
• Category 4 is primarily applicable to the industrial use water and
partial agricultural use water.
• Category 5 is not applicable for drinking purposes.
Mercury aqueous pollution
gold mining, and
industrial boilers in
• In areas of mercury contamination, larger and older fish tend to have
higher levels of mercury.
• Minamata disease is a neurological syndrome caused by
severe mercury poisoning by polluted water. Symptoms
include ataxia, numbness in the hands and feet, general muscle
weakness, narrowing of the field of vision, and damage
to hearing and speech
Nickel aqueous pollution
• The average concentration of nickel in drinking water in the United
States is between 2 and 4.3 ppb.
• Metallic nickel and some other nickel compounds are teratogenic
and carcinogenic to mammals. Nickel concentrations in plants are
usually 1 μg/g, and concentrations above 50 μg/g are toxic.
• Effects of nickel:
• Increased red blood cells (cancer)
• Increased protein in the urine
• Chronic bronchitis
• Reduced lung function
• Stomach aches
• Cancer of the lungs
Uranium aqueous pollution
• Uranium is a naturally and commonly occurring radioactive element
and found in water coming from power plants causing uranium
contained water pollution
• Uranium poisoning cause birth abnormalities including physical
deformities, neurological and mental disorders.
• Copper and zinc:
• Zn can lead to acute gastrointestinal and respiratory damages and
acute heart, brain and kidney damages, when they are in polluted
• High concentrations of these heavy metals in ground water can
negatively affect on crop growth, as these metals interfere with
metabolic functions in plants
• Cupper toxicity in water lead to Liver damage ,Kidney damage
,Neurologic damage, Weakness , Abdominal
pain, Nausea, Vomiting, Diarrhea, Lung damage and Coma.
Methods to purify the
water from elemental
Commonly used methods
- Chemical precipitation
- Ion exchange
- Reverse osmosis
- Solvent extraction
• Reverse Osmosis:
It is a process in which heavy metals are
separated by a semi-permeable membrane at a pressure greater than
osmotic pressure caused by the dissolved solids in wastewater. The
disadvantage of this method is that it is expensive.
• Direct contact membrane distillation (DCMD).
• Applicable to desalination. Heated seawater is
passed along the surface of a hydrophobic polymer
• Evaporated water passes from the hot side through
pores in the membrane into a stream of cold pure
water on the other side.
• The difference in vapour pressure between the hot
and cold side helps to push water molecules
• Ions exchange:
In this process, metal ions from dilute solutions are
exchanged with ions held by electrostatic forces on the
Different type of ion exchange resins used for every metal like
Lead : carboxylic resin
Uranium: WBA and SBA
• Chemical Precipitation:
Precipitation of metals is achieved
by the addition of coagulants such as alum, lime, iron salts and
other organic polymers. The large amount of sludge containing
toxic compounds produced during the process is the main
Heavy metals removal by biosorption
• The biosorption process involves a solid phase
(biological material) and a liquid phase (solvent,
normally water) containing a dissolved species to be
• The degree of sorbent affinity for the sorbate
determines its distribution between the solid and
• Many algae have immense capability to sorb metals,
and there is considerable potential for using them to
Heavy metals removal by Zeolites
• Zeolites are nature's powerful detoxifiers that are so strong they
even binds all those heavy metals from the food and water we
• natural zeolites can safely remove heavy metals such as
mercury, cadmium, lead, arsenic, aluminum, and tin, while also
removing radioactive metals like cesium and Strontium-90.
• Zeolites are microporous, aluminosilicate minerals
commonly used as commercial adsorbents.