Water Contaminants - Part 1
Water contaminants - Part 1
Brief information
limits of contaiminants for safe drinking water and Health effects.
1. Aluminium
Occurance:
Aluminum present in seawater approximately 0.013 and 5 ppb.
River water generally contains about 400 ppb of aluminum.
It occurs as Al3+ (acidic),as Al(OH)4- (neutral to alkalic). Other forms include AlOH2+, Al(OH)3.
Aluminum founds in variouse forms on earth:
As mineral: as feldspars, such as and orthoclase, anorthite, albite, micas and bauxite, and clay minerals. A number of gemstones contain aluminum, examples are ruby and sapphire.
Aluminum salts being used to precipitation for phosphate removal. water purification between pH6.8 and pH7.3 as hydroxides.
Some more examples of aluminum application are aluminum chloride, aluminum oxide, aluminum sulphate, and aluminum hydrogen as a reduction and hydration agent.
What are the environmental effects of aluminum in water?
Regular aluminum in groundwater is about 0.4 ppm, in soils as water insoluble hydroxide, At pH 4.5 solubility increases upto 5ppm or above. This may also occur at very high pH values.
Dissolved Al3+-ions are toxic to plants; these affect roots and decrease phosphate intake. Why dissolved aluminium by pH values increase aluminum dissolves because of acid rain dissolving soil aluminum increasing concentrations. At increasing nitrate deposition the aluminum amount increases, and decreases under large heather and agricultural surfaces.
Acid rain dissolves minerals in soils, and transports these to water sources. This may cause aluminum concentrations in rivers and lakes to rise.
Aluminum is toxic to fish in acidic at pH values 5.0-5.5, at a concentration of 0.1 mg/L. Simultaneous electrolyte shortages influence gull permeability, and damage surface gull cells When pH values decrease, aluminum ions influence gull permeability regulation by calcium causing sodium losses. This mainly concerns young animals. The element also influences growth of freshwater bony fish.
Only one non-radioactive aluminum isotope occurs naturally. There are eight instable isotopes.
What are the health effects of aluminum in water?
Aluminum concentration in the human body is approximately 9 ppm. In some organs, like spleen, kidneys and lung, concentrations up to 100 ppm may be present.
Daily aluminum intake is approximately 5 mg, of which absorbed a little. It is low acute toxicity. Daily usage is about 10 μg which is harmless to humans. Silicon decreases aluminum absorbance but once the element is absorbed in the body it is not easily removed.
Large quatity may negatively influence the health.
Nerve damage, kidney may damage may be due to aluminum toxicity, risk of allergies.
Aluminum may be mutagenic and carcinogenic.
Aluminum may increase number of Alzheimer cases.
However, Aluminum concentrations always increase with age.
Aluminum increased intake may also cause osteomalacia (vitamin D and calcium deficits).
Aluminum intake through food and drinking water between 50 and 200 μg/L. Aluminum particles may cause functional lung disorder.
Aluminum chloride may corrode the skin, irritate the mucous membranes in the eyes, and cause perspiration, shortness of breath and coughing. Alum increases blood clotting.
How to remove aluminium from water
Aluminum can be removed from water by:
ion exchange or coagulation/ flocculation.
Aluminum salts can be used in water treatment for precipitation reactions.
Adding aluminum sulphate and lime to water forming aluminum hydroxide which leads to settling of pollutants. Hydroxide is insoluble in water and remains upto 0.05 ppm dissolved aluminum remains.
This is below the legal limit for drinking water of the World Health Organization (WHO), of 0.2 ppm aluminum.
2. Argon (Ar) and water
After nitrogen and oxygen, argon is the most abundant element in air (0.993% volume). Seawater contains about 0.45 ppm argon.
Argon is a noble gas and it does not react with any other element.
Solubility of argon and argon compounds
Soluable in water upto 62 mg/L at 20oC at 1 bar pressure
Argon does not remain dissolved in water and did not go higher than normal concentrations.
Why is argon present in water?
Argon occurs inseveral potassium minerals by radioactive decay of the 40K isotope. for commercial purposes it is extracted from fluid air by 750,000 tons annually. Argon protect sphere, because it is very unreactive. In fluorescent lamps it aids the starting mechanism and glows blue. The argon is being used in steel industries to trap the air to protect heated metal from oxidation.
Argon is applied to protect other elemental effects. Also applied as a protective coating from temperature change, for example as insulation in the double-glazing. Argon is being used in tyres industries to protect rubber for noise emission at high speed. Also used argon laser for eye correction and tumor removal. The potassium-argon method is applied in geology to date solidification time of volcanic materials. Argon is a by-product of fractioned distillation for hydrogen production.
What are the environmental effects of argon in water?
Argon is non-water hazardous and no known environmental effects have occurred.
Argon naturally has three stable isotopes, and we now know of nine instable isotopes.
What are the health effects of argon in water?
Argon found in the human body in trace amounts. Argon is physiologically ineffective. Health effects from argon present in drinking water are not expected.
The only health effect is argon accumulation in air that is breathed in, may cause oxygen deprivation and asphyxiation. Exposure time if exceeds to argon may cause nausea, sleepiness, breathlessness, unconsciousness, and possible death by asphyxiation.
Removal of argon from water is insignificant.
3. Arsenic (As) and water
Arsenic and water: reaction mechanisms, environmental impact and health effects
Arsenic in seawater (2-4 ppb), and in rivers (0.5-2 ppb). Fresh water and seas algae contain about 1-250 ppm of arsenic, and fishes 0.2-320 ppm (all values are based on dry mass). In algae and shrimp, arsenic can be found in organic compounds.
The legal limit for arsenic in water applied by the World Health Organization (WHO) is 10 μg/L.
How arsenic react with water?
It does not react with dry air, but when it comes in contact with moist air a layer is formed. The layer has a bronze colour, and later develops a black surface.
An example of an arsenic compounds that reacts strongly with water is orpiment. This is an amorphous arsenic compound. Reaction mechanism:
As2S3 + 6 H2O -> 2 H3AsO3 + 3 H2S
In water arsenic participates in oxidation and reduction reactions, coagulation and adsorption. Adsorption of arsenic to fine particles in water and precipitation with aluminium or iron hydroxides causes arsenic to enter sediments. After some time arsenic may dissolve once again consequential to reduction reactions.
Solubility of arsenic and arsenic compounds
Elementary arsenic is insoluble, whereas arsenic compounds may readily dissolve.
Examples of solubility of arsenic compounds: arsenic(III)hydride 700 mg/L, arsenic(III)oxide 20 g/L, arsenic acid (H3AsO4.1/2 H2O) 170 g/L, and arsenic(III)sulfide 0.5 mg/L.
Why is arsenic present in water?
Arsenic and its compounds abundantly found in the earth's crust. Arsenic from rocks and soils dissolves in groundwater. Arsenic level found high in groundwater due to geothermal activity.
Arsenic is applied in different shapes and forms, and can enter water bodies as such. Enormouse arsenic comes into earth crust from volcanic activity and a little quantity from fossil fuel combustion. Metallic arsenic from lead or copper alloys, to increase hardness. The extremely toxic arsenic gas ASH3 produced from microchip production. Copper arsenate (Cu3(AsO4)2.4H2O) is being used as a pesticide, but in many countries it is prohibited. Paxite (CuAs2) is an insecticide and fungicide.
Arsenic compounds used as a wood preservative,
In glass processing, in chemical industries,
In semiconductor technique together with gallium and indium.
In arsenic used in paint industries as a yellow pigment.
Arsenic was applied in chemical weapons during the first world war.
Dimethyl arsenic acid was applied for the destruction of rice cultures during Vietnam War.
Although the use of arsenic is decreasing less and less but still present in the environment in near mines, soil quantities of arsenic may still be up to 30 g/kg.
For medical purposes it is beingused for curing asthma, haematological illnesses, dermatosis and psychosis.
Watery solutions of potassium arsenide (Fowler solution) used to treat chronic bronchial asthma, syphilis and other diseases. Arsenic may assist in curing sleeping sickness and leukaemia.
Arsenic do not entered into human body from water intake, but by food intake like fish products, arsenic may enter meat, In vegitable arsenic enter through contaminated soils. In mushrooms up to 50 mg/kg dry matter were found.
What are the environmental effects of arsenic in water?
Arsenic used for protein synthesis in several animal species .
Arsenic concentration is 2-46 ppm in fresh water algae , for rats 20 mg/kg body mass for the carcinogenic arsenic(III)oxide. It also blocks enzymatic processes, increasing toxicity. In mice, hamsters and rats was embryo toxic and teratogenic.
only one stable arsenic isotope exists in nature out of 19 other instable isotopes discovered up till now.
What are the health effects of arsenic in water?
Through contaminated drinking water In the old days it was applied as a poison, resembling cholera symptoms, and therefore the intentional factor was shaded.
As essential for some plant and animal species. A possible safe dose for humans if it is a dietary mineral upto 15-25 μg This can be absorbed from food without any trouble. In a human body it is about 0.5-15 mg which can be absorb 60 to 90% but can be easily excreted. Resently in human body can be absorbed in liver, spleen, lungs and digestive tract. Most arsenic is excreted, and residues may be found in skin, hair, nails, legs and teeth.
Under conditions of prolonged exposure, many organs may be damaged, skin pigmentation may occur, hair may fall out and nail growth may stop.
Toxicity in different arsenic comound are different in various arsenic compounds like monomethyl arsenic acid and inorganic arsenide have a higher toxicity level than arsenic choline. Toxicity is generally higher for inorganic arsenic compounds than for organic arsenic compounds. Oral intake more than 100 mg is lethal. The lethal dose of arsenic trioxide is 10-180 mg, for arsenide this is 70-210 mg. Symptoms of acute arsenic poisoning are nausea, vomiting, diarrhoea, cyanosis, cardiac arrhythmia, confusion and hallucinations. Symptoms of chronic arsenic poisoning are depression, numbness, sleeping disorders and headaches.
Arsenic related health effects are not acute, but mainly skin cancer. Arsenic may cause low birth weight and spontaneous abortion.
Arsenic in drinking water is an issue of global importance, the legal limit 10 μg/L. This legal limit is not met in several countries like Vietnam and Bangladesh, where the people are consume drinking water over 50 μg/L of arsenic producing several health effects like skin disease, skin cancer, and tumours in lungs, bladder, kidneys and liver.
_____________________________________________________________________
Read more about the arsenic problem in Bangladesh in my separate blog
The Bangladesh arsenic crisis
The poisonous Arsenic is found in three forms; yellow, grey and black arsenic. It is used as pesticides. It is toxic to insects, some plants, and also to humans.
Bangladesh, Asia has had drinking water problems because of using surface water for drinking for several decade causing cholera and dysentery. Some other countries like Vietnam, Cambodia and Tibet having similiar geological environments as Bangladesh. These countries may also have high-arsenic groundwater.
About 57 million Bangladeshi people started drinking groundwater with arsenic far above the legal limit of 0,05 mg/L. After several years using drinking water over a quarter of the Bangladeshi people suffering of arsenic poisoning (arsenicosis).
Arsenic poisoning kills people by digestive problem plus skin colour, formation of skin patches, stomach pains, vomiting, delirium and gangrene. Low level of arsenic results in cancers, such as lung cancer, skin cancer, kidney cancer and bladder cancer.
In the early 1980 the arsenic crisis was descovered but no solution was found until the mid-1990. The World Health Organisation found this as the largest mass poisoning of a population in history.Untill today, more than 85 million Bangladeshi are drinking the arsenic-rich groundwater and about at least 80 million people now suffer from arsenic poisoning.
Legal proceedings began in London in 2003 to determine whether the
British Geological Survey in London in 2003 detect arsenic in Bangladeshi water supplies and was negligent in failing to. And conducted research on behalf of the Bangladesh government in 1992, but did not test the groundwater for arsenic.
_____________________________________________________________________
Arsenic removal from water?
Ion exchange, membrane filtration, and iron and aluminium coagulation are usually being used to eliminate arsenic from water which mainly contains inorganic arsenic (arsenide or arsenate), So the total arsenic concentration suffices.
In soil it can be remove from soils by applying ferns that bioaccumulate large arsenic concentrations.
Read more: https://www.lenntech.com/environmental-disasters.htm#ixzz5a9oQRZW7
4. Boron in water
Boron found in seawater about 4-5 ppm and 10 ppb in river water,in seaweed 8-15 ppm and in mussels 4-5 ppm.
When dissolve in water forms B(OH)3 (aq) or B(OH)4- (aq).
Normally boron does not react with water. Some compounds like boron trifluoride ethyl ether complex reacts with water forming diethyl ether BF3 releasing some highly flammable gases. Some compounds like boron tri iodide, are hydrolysed in water.
Boron salts solubility: Boric acid solubility of 57 g/L, borax of 25.2 g/L, and boron trioxide of 22 g/L.
Boron trifluoride has the least soluble that is 2.4 g/L. and Boron Nitrite is comletly insoluble.
Boron minerals are Kernite, borax, ulexite and colemanite, also found in variouse rock formations. Some soil contains boron between 5 and 80 ppm. Boron found in several places in exessive qantity in the form of boric acid, borates and boron minerals.The combination with soil depends on pH value. Due to climatic effects boron from soil released and enter into water.
Pure element is rarely used, except for metal boride production, or to enhance aluminum conductivity to be utilize in some particulare use like turbines, rocket power for high-temperature reactions, and electrodes. Boron enhance hardness of steel.
Sodium perborate is used in detergents for bleaching purposes forming Borate which could damage water plants. Borates act as water softeners. Some compounds used in glass, glass fibre, ceramic and email production. To solidify and heat resistant boron boron is added in glass industry and glass fibres are applied as insulation. Boron compounds used as cleansing agents, in batteries and eye drops like borax, boron oxide and boric acid. Boric acid and borax also execcively used in fertilizers and pesticides. It is illegal preservatives in food products, wood preservatives. it is applied as an abrasive as boron carbide and boron nitrite.
Boron has a special function in a polymer matrix and In nuclear reactors as a cooling agent and also absorbs neutrons in the reactor core.
It is a dietary requirement for many organisms, an important role in mitosis. Usefull In green algae, and plant species. Boron deficiencies may cause in growth problems and sugar mobilization. It absorbed as boric acid. In plants 30-75 ppm of boron found.It may be toxic over 100 ppm decreasing crop yield. no effects on grass species with high boron. However, trees need boron as compared to other plant species. A tolerable boron in soils is approximately 25 ppm.
For water plants 10 - 300mg/l borate is hazardous and also toxic for fish species.
Boron is not a dietary requirement for vertebrates.
Boric acid is mildly hazardous in water but with halogens strongly hazardous.
Boron consists of two stable and fourteen instable isotopes.
Health effects of boron in water?
Boron present in human body about 0.7 ppm,it is not a dietary requirement. In human body it absorb from food stuffs, as plant needs it as dietary requirement which is about 2 mg. The amount of boron present in fruits and vegetables is below the toxicity boundary.
Over 5 g of boric acid the human body is negatively influenced, causing nausea, vomiting, diarrhoea and blood clotting and over 20 g are life threatening. Boric acid irritates the skin and eyes. Skin contact with boron trifluoride may cause corrosion.
A possible amount of boron in soils and drinking water, and the occurrence of arthritis among people.
Both boric acid and borax are used in medicine in certain amounts. As neutron absorb Boron it is applied in brain tumour treatment (boron neutron capture therapy).
Removal of boron from water?
As boron occure in nature as boric acid and its salts. It can be removed by ion exchangers, but very slowly, because of its resemblance to silicate.
5. Calcium (Ca) and water
Calcium and water: reaction mechanisms, environmental impact and health effects
Calcium occurs in water naturally. Seawater contains approximately 400 ppm calcium. One of the main reasons for the abundance of calcium in water is its natural occurrence in the earth's crust. Calcium is also a constituent of coral.
River water generally contain 1-2 ppm calcium, but in lime areas rivers may contains calcium as high as 100 ppm.
Examples of calcium in water organisms: seaweed luctuca 800-6500 ppm (moist mass), oysters approximately 1500 ppm (dry mass).
In a watery solution calcium is mainly present as Ca2+ (aq), but it may also occur as CaOH+ (aq) or Ca(OH)2 (aq), or as CaSO4 in seawater.
Calcium is an important determinant of water hardness, and it also functions as a pH stabilizer, because of its buffering qualities. Calcium also gives water a better taste.
Calcium reaction with water?
As magnesium placed above calcium in the periodic chart, elementary calcium reacts with water at room temperature, according to the following reaction mechanism:
Ca (s) + 2H2O (g) -> Ca(OH)2 (aq) + H2 (g)
This reaction forms calcium hydroxide that dissolves in water as a soda, and hydrogen gas.
Calcium also act as erosion reactions in the presence of carbon dioxide. As calcium carbonate is water insoluble. In presence of carbon dioxide, carbonic acid is formed, affecting calcium compounds.
The reaction mechanism in weather:
H2O + CO2 -> H2CO3 and CaCO3 + H2CO3 -> Ca(HCO3)2
And the total reaction mechanism:
CaCO3 (s) + CO2 (g) + 2H2O (l) -> Ca2+ (aq) + 2 HCO3- (aq)
The product is calcium hydrogen carbonate.
Solubility of calcium and calcium compounds:
Calcium reacts with water. Calcium compounds are more or less soluble in water. Solubility of Calcium carbonate is 14 mg/L, but become five times in presence of carbon dioxide.
Solubility of calcium phosphate is 20 mg/L,
and calcium fluoride is 16 mg/L.
Calcium chromate solubility is 170 g/L, and at 0oC
Calcium hypo chlorate solubility is 218 g/L.
Solubility of calcium arsenate 140 mg/L,
Calcium hydroxide 1.3 g/L
and calcium sulphate 2.7-8.8 g/L.
Why is calcium present in water?
Calcium present in water due to the presence of carbon dioxide from air to water forming carbonic acid which dissolve rocks like limestone, marble, calcite, dolomite, gypsum, fluorite and apatite.
Water hardness is because of Ca2+ ions as well as magnesium as hardness determinant.
Calcium is used in cement, brick lime and concrete. It is also present in batteries, applied in plaster as calcium sulphate. Calcium also used in zirconium and thorium production. In steal industries calcium is used as a blotter, and is added to aluminium, copper and lead alloys. Calcium can extract sulphur dioxide from industrial exhaust, and neutralize sulphuric acids before discharge.
Calcium also used as hypo chloride as bleach and for disinfection, calcium phosphate in glass and in porcelain industries, calcium polysulphide and hydroxide used as flocculants in wastewater treatment, and calcium fluoride as turbidity agent in enamel industries, in UV-spectroscopy, and used for fluid acid production.
Calcium also used for carbon and sulphur removal from iron and iron alloys, and for dewatering oil. Limestone is applied as a paper filler, causing paper to colour whiter, and in plastics to improve stability.
Calcium affects soil quality and various compounds and applied as a fertilizer. For example, CaCl2- or Ca(NO)3 solutions are applied in horticulture. Calcium oxide is used dehydrating.
Effects of calcium in water?
All organisms require calcium for dietary purposes. But some insects and bacteria require calcium carbonate for building skeletons of most marine organisms, and eye lenses. Calcium phosphate is need for bone and teeth structure of terrestrial organisms. Plants also contain calcium oxalate.
Water hardness require calcium, and not toxicity like copper, lead and zinc are much more toxic in water.
Water hardness effects aquatic organisms because of metal toxicity. Calcium also used as binding spots in the gills. so, hard water protects fishes from metal uptake. Calcium at pH level of 4.5-4.9 may harm salmon eggs and grown salmons, when the calcium, sodium and chlorine content is low.
Some calcium compounds may be toxic like LD50 of rats for calcium arsenite is 20 mg/ kg weight. Calcium carbide forms flammable ethyn when it comes in contact with water is hazardous.
Water hardness effects domestic equipment, in high temperatures forms carbonate hardness which decreases the lifespan of equipment. Calcium carbonate may causes a decrease in detergent efficiency, resulting the excess use of detergent.
Water softening can be done by ion exchangers which can be regenerates common salt.
Calcium have six stable isotopes eight instable calcium isotopes.
45Ca is highly radioactive and toxic.
Health effects of calcium in water?
Calcium is a dietary mineral requirement for human body in amounts of about 1.2 kg. Calcium phosphate is a supporting compound effecting bones and tooth growth, together with vitamin D.
Muscle tissue for muscle contractions , blood for clotting and cell membrane for growth and cell division also need calcium. Calcium for monitoring membrane activity to assists nerve impulse transfer and hormone release, pH stabilizes in the body making it to be a essential part of the body. For the body functions a daily intake of about 1000 mg of calcium is recommended for adults and can get from dairy, grains and green vegetables.
Calcium carbonate is acid remedy for stomach and can be used for digestive failure. For calcium deficiency, and calcium, calcium lactate may aid the body during periods of chloride is a diuretic.
Calcium in hard water strengthen bones and teeth. recommended hardness in drinking water must be above 8.4 odH. The presence of calcium carbonate effect on lead water pipes it forms a protective lead(II) carbonate coating protecting lead to dissolve in drinking water preventing lead to enter in the human body.
When one takes up large amounts of calcium dose of oral uptake about 5-50 mg/ kg body weight. Metallic calcium corrodes the skin when it comes in contact with skin, eyes and mucous membranes.
Purification technologies to remove calcium from water?
By water softeners, ion exchangers containing Na+ ions, which are released and substituted by Ca2+ and Mg2+ ions.
Calcium compounds can be used in wastewater treatment.
Hardness and pH may be adjusted by calcium carbonate and calcium hydroxide as according to the International Drinking Water Standards.
6. Chromium (Cr) and water
Chromium content in Sea water is between 0.2 and 0.6 ppb.
while in rivers water approximately 1 ppb of chromium. But due to some untreated industrial water the concentrations may possibly increase to 5-20 ppb in the River Rhine, and 10-40 ppb in the River Elbe in 1988.
Sea fish have 0.03 and 2 ppm, and oyster tissue 0.7 ppm (all values dry mass). Phytoplankton has a bio concentration factor of approximately 104 in seawater.
Chromium may be either anionic trivalent Cr(OH)3 or as hexavalent CrO42-. Chromium dissolved as Cr3+ ions is relatively low, because of its stable complexes.
Oxidation ranks from Cr(II) to Cr(VI). In natural waters trivalent chromium is most abundant.
Reaction of chromium with water
Chromium does not react with water at room temperature.
Chromium compounds are insoluble. Chromium (III) water insoluble because of bounding with floating particles in water. Chromium (III) oxide and chromium (III) hydroxide are the only water soluble compounds. Chromium (VI) oxide is an example of an excellently water soluble chromium compounds, solubility = 1680 g/L.
Chromite is a chrmium mineral. Chromium do not freely occure in nature.
Traces of chrmium compounds are found in water because of surface water from industrial discharge like metal surface refinery and in alloys. Stainless steel consists of 12-15% chromium. Chromium metal used worldwide approximately 20,000 tons per year. when used in coating or polishing do not oxidize by air.
Trivalent chromium mainly discharged from metal industry. Hexavalent chromium discharge from tanning( 90% leather tanning by chromium compounds) and painting industries as pigments. Wastewater usually have about 5 ppm of chromium. As a catalyser chrmium used in wood impregnation, audio and video production and in lasers. Chromite is the inflammable material and chemical production.
Chromium also usually present in domestic waste from some synthetic materials. In incineration it spread to the environment due to lake of protection.
51Cr isotope is released from nuclear fission which can be used for medical purposes.
Environmental effects of chromium in water?
It is a dietary requirement of several organisms as trivalent chromium.
Hexavalent chromium is toxic to flora and fauna.
Chromium water pollution is the most severe environmental problems, which is polluted from untreated wastewater in rivers.
Chromium (III) slightly water soluble, so concentration in natural waters are limited. Cr3+ ions at pH over 5 rarely found, because (Cr(OH)3)it is hardly soluble in water.
Chromium (VI) stable but are reduced to chromium (III) compounds under anaerobic conditions. The reaction is reversable. Chromium is floating as particles in water.
The LC50 value: in sea fish is between 7 and 400 ppm, for daphnia at 0.01-0.26 ppm, and for algae at 0.032-6.4 ppm.
Chromium (VI) in water hazard class 3, and very toxic.
Chromium phytotoxicity is undetermined. Concentrations between 500 to 6000 ppm in soils not harmfull for plants. Lime and or phosphate in soils decreases chromium. Dried soil contains 2-100 ppm of chromium. Its solubility in soil water is less than other toxic metals and so low plant uptake about 0.02-1 ppm chromium and may increase to 14 ppm. In mosses and lichens high concentrations can be found.
Chromium (VI) toxic for both plants and animals even low concentrations which is pH dependent. Chromium (VI) mobile in soils than chromium (III) compounds, and Chromium (VI) reduces to chromium (III) compounds within a short time. Soluble chromates converted to insoluble chromium (III) salts so uptake for plants decreases protecting the food chain from high chromium. Chromate mobility in soils depends on soil pH and soil absorption capacity, and on temperature. Chromium in agricultural soils is approximately 100 ppm.
Chromium has four stable isotopes and eight instable isotopes. The 51Cr, normally applied for diagnosis and have average degree of radioactivity.
What are the health effects of chromium in water?
The human body contains about 0.03 ppm of chromium and daily intake about 15-200 μg, and could be upto 1 mg. that is about 0.5-1%. The placenta is the organ with the highest chromium amounts.
Human body requirement of Trivalent chromium is essentially as a trace element. It removes glucose from blood, and is used in fat metabolism. Chromium deficiancy may cause diabetes symptoms.
Chromium (III) at recomended level do not shows to be toxic through food and drinking water. It may even improve health, and cure neuropathy and encephalopathy.
Hexavalent chromium has negative health impact and extreme toxicity. It causes allergic and asthmatic reactions, is carcinogenic. Hexavalent chromium is 1000 times toxic as compared to trivalent chromium. Hexavalent chromium exposes diarrhoea, stomach and intestinal bleedings, cramps, and liver and kidney damage and is mutagenic. Toxic effects may be transfer to children through the placenta.
Chromium (VI) oxide is a strong oxidant when dissolve form chromium acid which corrodes the organs and may cause cramps and paralysis due to high dose 1-2 g. Legal limit of 50 ppb chromium in drinking water.
In chromium industries illness may cause due to skin contact with chromates. Chromium trioxide dust uptake in the workplace may cause cancer, and damage the respirational tract.
Purification
Significant influence by drinking water quality. Normally a considerable ammount not found in groundwater and surface water. Specific removal in sewage water treatment is therefore unusual.
Chromium removal from water is ion exchangers and active carbon can be applied for this purpose.
it Precipitate as hydroxide, coagulation may not be a effective process to remove chromium(VI). Iron Sulphate can be used to reduce chromium(VI) to chromium III and can be removed but not usually used in drinking water preparation.
This is the end of Part One. Come back later for the next Part.
Brief information
limits of contaiminants for safe drinking water and Health effects.
1. Aluminium
Occurance:
Aluminum present in seawater approximately 0.013 and 5 ppb.
River water generally contains about 400 ppb of aluminum.
It occurs as Al3+ (acidic),as Al(OH)4- (neutral to alkalic). Other forms include AlOH2+, Al(OH)3.
Aluminum founds in variouse forms on earth:
As mineral: as feldspars, such as and orthoclase, anorthite, albite, micas and bauxite, and clay minerals. A number of gemstones contain aluminum, examples are ruby and sapphire.
Aluminum salts being used to precipitation for phosphate removal. water purification between pH6.8 and pH7.3 as hydroxides.
Some more examples of aluminum application are aluminum chloride, aluminum oxide, aluminum sulphate, and aluminum hydrogen as a reduction and hydration agent.
What are the environmental effects of aluminum in water?
Regular aluminum in groundwater is about 0.4 ppm, in soils as water insoluble hydroxide, At pH 4.5 solubility increases upto 5ppm or above. This may also occur at very high pH values.
Dissolved Al3+-ions are toxic to plants; these affect roots and decrease phosphate intake. Why dissolved aluminium by pH values increase aluminum dissolves because of acid rain dissolving soil aluminum increasing concentrations. At increasing nitrate deposition the aluminum amount increases, and decreases under large heather and agricultural surfaces.
Acid rain dissolves minerals in soils, and transports these to water sources. This may cause aluminum concentrations in rivers and lakes to rise.
Aluminum is toxic to fish in acidic at pH values 5.0-5.5, at a concentration of 0.1 mg/L. Simultaneous electrolyte shortages influence gull permeability, and damage surface gull cells When pH values decrease, aluminum ions influence gull permeability regulation by calcium causing sodium losses. This mainly concerns young animals. The element also influences growth of freshwater bony fish.
Only one non-radioactive aluminum isotope occurs naturally. There are eight instable isotopes.
What are the health effects of aluminum in water?
Aluminum concentration in the human body is approximately 9 ppm. In some organs, like spleen, kidneys and lung, concentrations up to 100 ppm may be present.
Daily aluminum intake is approximately 5 mg, of which absorbed a little. It is low acute toxicity. Daily usage is about 10 μg which is harmless to humans. Silicon decreases aluminum absorbance but once the element is absorbed in the body it is not easily removed.
Large quatity may negatively influence the health.
Nerve damage, kidney may damage may be due to aluminum toxicity, risk of allergies.
Aluminum may be mutagenic and carcinogenic.
Aluminum may increase number of Alzheimer cases.
However, Aluminum concentrations always increase with age.
Aluminum increased intake may also cause osteomalacia (vitamin D and calcium deficits).
Aluminum intake through food and drinking water between 50 and 200 μg/L. Aluminum particles may cause functional lung disorder.
Aluminum chloride may corrode the skin, irritate the mucous membranes in the eyes, and cause perspiration, shortness of breath and coughing. Alum increases blood clotting.
How to remove aluminium from water
Aluminum can be removed from water by:
ion exchange or coagulation/ flocculation.
Aluminum salts can be used in water treatment for precipitation reactions.
Adding aluminum sulphate and lime to water forming aluminum hydroxide which leads to settling of pollutants. Hydroxide is insoluble in water and remains upto 0.05 ppm dissolved aluminum remains.
This is below the legal limit for drinking water of the World Health Organization (WHO), of 0.2 ppm aluminum.
2. Argon (Ar) and water
After nitrogen and oxygen, argon is the most abundant element in air (0.993% volume). Seawater contains about 0.45 ppm argon.
Argon is a noble gas and it does not react with any other element.
Solubility of argon and argon compounds
Soluable in water upto 62 mg/L at 20oC at 1 bar pressure
Argon does not remain dissolved in water and did not go higher than normal concentrations.
Why is argon present in water?
Argon occurs inseveral potassium minerals by radioactive decay of the 40K isotope. for commercial purposes it is extracted from fluid air by 750,000 tons annually. Argon protect sphere, because it is very unreactive. In fluorescent lamps it aids the starting mechanism and glows blue. The argon is being used in steel industries to trap the air to protect heated metal from oxidation.
Argon is applied to protect other elemental effects. Also applied as a protective coating from temperature change, for example as insulation in the double-glazing. Argon is being used in tyres industries to protect rubber for noise emission at high speed. Also used argon laser for eye correction and tumor removal. The potassium-argon method is applied in geology to date solidification time of volcanic materials. Argon is a by-product of fractioned distillation for hydrogen production.
What are the environmental effects of argon in water?
Argon is non-water hazardous and no known environmental effects have occurred.
Argon naturally has three stable isotopes, and we now know of nine instable isotopes.
What are the health effects of argon in water?
Argon found in the human body in trace amounts. Argon is physiologically ineffective. Health effects from argon present in drinking water are not expected.
The only health effect is argon accumulation in air that is breathed in, may cause oxygen deprivation and asphyxiation. Exposure time if exceeds to argon may cause nausea, sleepiness, breathlessness, unconsciousness, and possible death by asphyxiation.
Removal of argon from water is insignificant.
3. Arsenic (As) and water
Arsenic and water: reaction mechanisms, environmental impact and health effects
Arsenic in seawater (2-4 ppb), and in rivers (0.5-2 ppb). Fresh water and seas algae contain about 1-250 ppm of arsenic, and fishes 0.2-320 ppm (all values are based on dry mass). In algae and shrimp, arsenic can be found in organic compounds.
The legal limit for arsenic in water applied by the World Health Organization (WHO) is 10 μg/L.
How arsenic react with water?
It does not react with dry air, but when it comes in contact with moist air a layer is formed. The layer has a bronze colour, and later develops a black surface.
An example of an arsenic compounds that reacts strongly with water is orpiment. This is an amorphous arsenic compound. Reaction mechanism:
As2S3 + 6 H2O -> 2 H3AsO3 + 3 H2S
In water arsenic participates in oxidation and reduction reactions, coagulation and adsorption. Adsorption of arsenic to fine particles in water and precipitation with aluminium or iron hydroxides causes arsenic to enter sediments. After some time arsenic may dissolve once again consequential to reduction reactions.
Solubility of arsenic and arsenic compounds
Elementary arsenic is insoluble, whereas arsenic compounds may readily dissolve.
Examples of solubility of arsenic compounds: arsenic(III)hydride 700 mg/L, arsenic(III)oxide 20 g/L, arsenic acid (H3AsO4.1/2 H2O) 170 g/L, and arsenic(III)sulfide 0.5 mg/L.
Why is arsenic present in water?
Arsenic and its compounds abundantly found in the earth's crust. Arsenic from rocks and soils dissolves in groundwater. Arsenic level found high in groundwater due to geothermal activity.
Arsenic is applied in different shapes and forms, and can enter water bodies as such. Enormouse arsenic comes into earth crust from volcanic activity and a little quantity from fossil fuel combustion. Metallic arsenic from lead or copper alloys, to increase hardness. The extremely toxic arsenic gas ASH3 produced from microchip production. Copper arsenate (Cu3(AsO4)2.4H2O) is being used as a pesticide, but in many countries it is prohibited. Paxite (CuAs2) is an insecticide and fungicide.
Arsenic compounds used as a wood preservative,
In glass processing, in chemical industries,
In semiconductor technique together with gallium and indium.
In arsenic used in paint industries as a yellow pigment.
Arsenic was applied in chemical weapons during the first world war.
Dimethyl arsenic acid was applied for the destruction of rice cultures during Vietnam War.
Although the use of arsenic is decreasing less and less but still present in the environment in near mines, soil quantities of arsenic may still be up to 30 g/kg.
For medical purposes it is beingused for curing asthma, haematological illnesses, dermatosis and psychosis.
Watery solutions of potassium arsenide (Fowler solution) used to treat chronic bronchial asthma, syphilis and other diseases. Arsenic may assist in curing sleeping sickness and leukaemia.
Arsenic do not entered into human body from water intake, but by food intake like fish products, arsenic may enter meat, In vegitable arsenic enter through contaminated soils. In mushrooms up to 50 mg/kg dry matter were found.
What are the environmental effects of arsenic in water?
Arsenic used for protein synthesis in several animal species .
Arsenic concentration is 2-46 ppm in fresh water algae , for rats 20 mg/kg body mass for the carcinogenic arsenic(III)oxide. It also blocks enzymatic processes, increasing toxicity. In mice, hamsters and rats was embryo toxic and teratogenic.
only one stable arsenic isotope exists in nature out of 19 other instable isotopes discovered up till now.
What are the health effects of arsenic in water?
Through contaminated drinking water In the old days it was applied as a poison, resembling cholera symptoms, and therefore the intentional factor was shaded.
As essential for some plant and animal species. A possible safe dose for humans if it is a dietary mineral upto 15-25 μg This can be absorbed from food without any trouble. In a human body it is about 0.5-15 mg which can be absorb 60 to 90% but can be easily excreted. Resently in human body can be absorbed in liver, spleen, lungs and digestive tract. Most arsenic is excreted, and residues may be found in skin, hair, nails, legs and teeth.
Under conditions of prolonged exposure, many organs may be damaged, skin pigmentation may occur, hair may fall out and nail growth may stop.
Toxicity in different arsenic comound are different in various arsenic compounds like monomethyl arsenic acid and inorganic arsenide have a higher toxicity level than arsenic choline. Toxicity is generally higher for inorganic arsenic compounds than for organic arsenic compounds. Oral intake more than 100 mg is lethal. The lethal dose of arsenic trioxide is 10-180 mg, for arsenide this is 70-210 mg. Symptoms of acute arsenic poisoning are nausea, vomiting, diarrhoea, cyanosis, cardiac arrhythmia, confusion and hallucinations. Symptoms of chronic arsenic poisoning are depression, numbness, sleeping disorders and headaches.
Arsenic related health effects are not acute, but mainly skin cancer. Arsenic may cause low birth weight and spontaneous abortion.
Arsenic in drinking water is an issue of global importance, the legal limit 10 μg/L. This legal limit is not met in several countries like Vietnam and Bangladesh, where the people are consume drinking water over 50 μg/L of arsenic producing several health effects like skin disease, skin cancer, and tumours in lungs, bladder, kidneys and liver.
_____________________________________________________________________
Read more about the arsenic problem in Bangladesh in my separate blog
The Bangladesh arsenic crisis
The poisonous Arsenic is found in three forms; yellow, grey and black arsenic. It is used as pesticides. It is toxic to insects, some plants, and also to humans.
Bangladesh, Asia has had drinking water problems because of using surface water for drinking for several decade causing cholera and dysentery. Some other countries like Vietnam, Cambodia and Tibet having similiar geological environments as Bangladesh. These countries may also have high-arsenic groundwater.
About 57 million Bangladeshi people started drinking groundwater with arsenic far above the legal limit of 0,05 mg/L. After several years using drinking water over a quarter of the Bangladeshi people suffering of arsenic poisoning (arsenicosis).
Arsenic poisoning kills people by digestive problem plus skin colour, formation of skin patches, stomach pains, vomiting, delirium and gangrene. Low level of arsenic results in cancers, such as lung cancer, skin cancer, kidney cancer and bladder cancer.
In the early 1980 the arsenic crisis was descovered but no solution was found until the mid-1990. The World Health Organisation found this as the largest mass poisoning of a population in history.Untill today, more than 85 million Bangladeshi are drinking the arsenic-rich groundwater and about at least 80 million people now suffer from arsenic poisoning.
Legal proceedings began in London in 2003 to determine whether the
British Geological Survey in London in 2003 detect arsenic in Bangladeshi water supplies and was negligent in failing to. And conducted research on behalf of the Bangladesh government in 1992, but did not test the groundwater for arsenic.
_____________________________________________________________________
Arsenic removal from water?
Ion exchange, membrane filtration, and iron and aluminium coagulation are usually being used to eliminate arsenic from water which mainly contains inorganic arsenic (arsenide or arsenate), So the total arsenic concentration suffices.
In soil it can be remove from soils by applying ferns that bioaccumulate large arsenic concentrations.
Read more: https://www.lenntech.com/environmental-disasters.htm#ixzz5a9oQRZW7
4. Boron in water
Boron found in seawater about 4-5 ppm and 10 ppb in river water,in seaweed 8-15 ppm and in mussels 4-5 ppm.
When dissolve in water forms B(OH)3 (aq) or B(OH)4- (aq).
Normally boron does not react with water. Some compounds like boron trifluoride ethyl ether complex reacts with water forming diethyl ether BF3 releasing some highly flammable gases. Some compounds like boron tri iodide, are hydrolysed in water.
Boron salts solubility: Boric acid solubility of 57 g/L, borax of 25.2 g/L, and boron trioxide of 22 g/L.
Boron trifluoride has the least soluble that is 2.4 g/L. and Boron Nitrite is comletly insoluble.
Boron minerals are Kernite, borax, ulexite and colemanite, also found in variouse rock formations. Some soil contains boron between 5 and 80 ppm. Boron found in several places in exessive qantity in the form of boric acid, borates and boron minerals.The combination with soil depends on pH value. Due to climatic effects boron from soil released and enter into water.
Pure element is rarely used, except for metal boride production, or to enhance aluminum conductivity to be utilize in some particulare use like turbines, rocket power for high-temperature reactions, and electrodes. Boron enhance hardness of steel.
Sodium perborate is used in detergents for bleaching purposes forming Borate which could damage water plants. Borates act as water softeners. Some compounds used in glass, glass fibre, ceramic and email production. To solidify and heat resistant boron boron is added in glass industry and glass fibres are applied as insulation. Boron compounds used as cleansing agents, in batteries and eye drops like borax, boron oxide and boric acid. Boric acid and borax also execcively used in fertilizers and pesticides. It is illegal preservatives in food products, wood preservatives. it is applied as an abrasive as boron carbide and boron nitrite.
Boron has a special function in a polymer matrix and In nuclear reactors as a cooling agent and also absorbs neutrons in the reactor core.
It is a dietary requirement for many organisms, an important role in mitosis. Usefull In green algae, and plant species. Boron deficiencies may cause in growth problems and sugar mobilization. It absorbed as boric acid. In plants 30-75 ppm of boron found.It may be toxic over 100 ppm decreasing crop yield. no effects on grass species with high boron. However, trees need boron as compared to other plant species. A tolerable boron in soils is approximately 25 ppm.
For water plants 10 - 300mg/l borate is hazardous and also toxic for fish species.
Boron is not a dietary requirement for vertebrates.
Boric acid is mildly hazardous in water but with halogens strongly hazardous.
Boron consists of two stable and fourteen instable isotopes.
Health effects of boron in water?
Boron present in human body about 0.7 ppm,it is not a dietary requirement. In human body it absorb from food stuffs, as plant needs it as dietary requirement which is about 2 mg. The amount of boron present in fruits and vegetables is below the toxicity boundary.
Over 5 g of boric acid the human body is negatively influenced, causing nausea, vomiting, diarrhoea and blood clotting and over 20 g are life threatening. Boric acid irritates the skin and eyes. Skin contact with boron trifluoride may cause corrosion.
A possible amount of boron in soils and drinking water, and the occurrence of arthritis among people.
Both boric acid and borax are used in medicine in certain amounts. As neutron absorb Boron it is applied in brain tumour treatment (boron neutron capture therapy).
Removal of boron from water?
As boron occure in nature as boric acid and its salts. It can be removed by ion exchangers, but very slowly, because of its resemblance to silicate.
5. Calcium (Ca) and water
Calcium and water: reaction mechanisms, environmental impact and health effects
Calcium occurs in water naturally. Seawater contains approximately 400 ppm calcium. One of the main reasons for the abundance of calcium in water is its natural occurrence in the earth's crust. Calcium is also a constituent of coral.
River water generally contain 1-2 ppm calcium, but in lime areas rivers may contains calcium as high as 100 ppm.
Examples of calcium in water organisms: seaweed luctuca 800-6500 ppm (moist mass), oysters approximately 1500 ppm (dry mass).
In a watery solution calcium is mainly present as Ca2+ (aq), but it may also occur as CaOH+ (aq) or Ca(OH)2 (aq), or as CaSO4 in seawater.
Calcium is an important determinant of water hardness, and it also functions as a pH stabilizer, because of its buffering qualities. Calcium also gives water a better taste.
Calcium reaction with water?
As magnesium placed above calcium in the periodic chart, elementary calcium reacts with water at room temperature, according to the following reaction mechanism:
Ca (s) + 2H2O (g) -> Ca(OH)2 (aq) + H2 (g)
This reaction forms calcium hydroxide that dissolves in water as a soda, and hydrogen gas.
Calcium also act as erosion reactions in the presence of carbon dioxide. As calcium carbonate is water insoluble. In presence of carbon dioxide, carbonic acid is formed, affecting calcium compounds.
The reaction mechanism in weather:
H2O + CO2 -> H2CO3 and CaCO3 + H2CO3 -> Ca(HCO3)2
And the total reaction mechanism:
CaCO3 (s) + CO2 (g) + 2H2O (l) -> Ca2+ (aq) + 2 HCO3- (aq)
The product is calcium hydrogen carbonate.
Solubility of calcium and calcium compounds:
Calcium reacts with water. Calcium compounds are more or less soluble in water. Solubility of Calcium carbonate is 14 mg/L, but become five times in presence of carbon dioxide.
Solubility of calcium phosphate is 20 mg/L,
and calcium fluoride is 16 mg/L.
Calcium chromate solubility is 170 g/L, and at 0oC
Calcium hypo chlorate solubility is 218 g/L.
Solubility of calcium arsenate 140 mg/L,
Calcium hydroxide 1.3 g/L
and calcium sulphate 2.7-8.8 g/L.
Why is calcium present in water?
Calcium present in water due to the presence of carbon dioxide from air to water forming carbonic acid which dissolve rocks like limestone, marble, calcite, dolomite, gypsum, fluorite and apatite.
Water hardness is because of Ca2+ ions as well as magnesium as hardness determinant.
Calcium is used in cement, brick lime and concrete. It is also present in batteries, applied in plaster as calcium sulphate. Calcium also used in zirconium and thorium production. In steal industries calcium is used as a blotter, and is added to aluminium, copper and lead alloys. Calcium can extract sulphur dioxide from industrial exhaust, and neutralize sulphuric acids before discharge.
Calcium also used as hypo chloride as bleach and for disinfection, calcium phosphate in glass and in porcelain industries, calcium polysulphide and hydroxide used as flocculants in wastewater treatment, and calcium fluoride as turbidity agent in enamel industries, in UV-spectroscopy, and used for fluid acid production.
Calcium also used for carbon and sulphur removal from iron and iron alloys, and for dewatering oil. Limestone is applied as a paper filler, causing paper to colour whiter, and in plastics to improve stability.
Calcium affects soil quality and various compounds and applied as a fertilizer. For example, CaCl2- or Ca(NO)3 solutions are applied in horticulture. Calcium oxide is used dehydrating.
Effects of calcium in water?
All organisms require calcium for dietary purposes. But some insects and bacteria require calcium carbonate for building skeletons of most marine organisms, and eye lenses. Calcium phosphate is need for bone and teeth structure of terrestrial organisms. Plants also contain calcium oxalate.
Water hardness require calcium, and not toxicity like copper, lead and zinc are much more toxic in water.
Water hardness effects aquatic organisms because of metal toxicity. Calcium also used as binding spots in the gills. so, hard water protects fishes from metal uptake. Calcium at pH level of 4.5-4.9 may harm salmon eggs and grown salmons, when the calcium, sodium and chlorine content is low.
Some calcium compounds may be toxic like LD50 of rats for calcium arsenite is 20 mg/ kg weight. Calcium carbide forms flammable ethyn when it comes in contact with water is hazardous.
Water hardness effects domestic equipment, in high temperatures forms carbonate hardness which decreases the lifespan of equipment. Calcium carbonate may causes a decrease in detergent efficiency, resulting the excess use of detergent.
Water softening can be done by ion exchangers which can be regenerates common salt.
Calcium have six stable isotopes eight instable calcium isotopes.
45Ca is highly radioactive and toxic.
Health effects of calcium in water?
Calcium is a dietary mineral requirement for human body in amounts of about 1.2 kg. Calcium phosphate is a supporting compound effecting bones and tooth growth, together with vitamin D.
Muscle tissue for muscle contractions , blood for clotting and cell membrane for growth and cell division also need calcium. Calcium for monitoring membrane activity to assists nerve impulse transfer and hormone release, pH stabilizes in the body making it to be a essential part of the body. For the body functions a daily intake of about 1000 mg of calcium is recommended for adults and can get from dairy, grains and green vegetables.
Calcium carbonate is acid remedy for stomach and can be used for digestive failure. For calcium deficiency, and calcium, calcium lactate may aid the body during periods of chloride is a diuretic.
Calcium in hard water strengthen bones and teeth. recommended hardness in drinking water must be above 8.4 odH. The presence of calcium carbonate effect on lead water pipes it forms a protective lead(II) carbonate coating protecting lead to dissolve in drinking water preventing lead to enter in the human body.
When one takes up large amounts of calcium dose of oral uptake about 5-50 mg/ kg body weight. Metallic calcium corrodes the skin when it comes in contact with skin, eyes and mucous membranes.
Purification technologies to remove calcium from water?
By water softeners, ion exchangers containing Na+ ions, which are released and substituted by Ca2+ and Mg2+ ions.
Calcium compounds can be used in wastewater treatment.
Hardness and pH may be adjusted by calcium carbonate and calcium hydroxide as according to the International Drinking Water Standards.
6. Chromium (Cr) and water
Chromium content in Sea water is between 0.2 and 0.6 ppb.
while in rivers water approximately 1 ppb of chromium. But due to some untreated industrial water the concentrations may possibly increase to 5-20 ppb in the River Rhine, and 10-40 ppb in the River Elbe in 1988.
Sea fish have 0.03 and 2 ppm, and oyster tissue 0.7 ppm (all values dry mass). Phytoplankton has a bio concentration factor of approximately 104 in seawater.
Chromium may be either anionic trivalent Cr(OH)3 or as hexavalent CrO42-. Chromium dissolved as Cr3+ ions is relatively low, because of its stable complexes.
Oxidation ranks from Cr(II) to Cr(VI). In natural waters trivalent chromium is most abundant.
Reaction of chromium with water
Chromium does not react with water at room temperature.
Chromium compounds are insoluble. Chromium (III) water insoluble because of bounding with floating particles in water. Chromium (III) oxide and chromium (III) hydroxide are the only water soluble compounds. Chromium (VI) oxide is an example of an excellently water soluble chromium compounds, solubility = 1680 g/L.
Chromite is a chrmium mineral. Chromium do not freely occure in nature.
Traces of chrmium compounds are found in water because of surface water from industrial discharge like metal surface refinery and in alloys. Stainless steel consists of 12-15% chromium. Chromium metal used worldwide approximately 20,000 tons per year. when used in coating or polishing do not oxidize by air.
Trivalent chromium mainly discharged from metal industry. Hexavalent chromium discharge from tanning( 90% leather tanning by chromium compounds) and painting industries as pigments. Wastewater usually have about 5 ppm of chromium. As a catalyser chrmium used in wood impregnation, audio and video production and in lasers. Chromite is the inflammable material and chemical production.
Chromium also usually present in domestic waste from some synthetic materials. In incineration it spread to the environment due to lake of protection.
51Cr isotope is released from nuclear fission which can be used for medical purposes.
Environmental effects of chromium in water?
It is a dietary requirement of several organisms as trivalent chromium.
Hexavalent chromium is toxic to flora and fauna.
Chromium water pollution is the most severe environmental problems, which is polluted from untreated wastewater in rivers.
Chromium (III) slightly water soluble, so concentration in natural waters are limited. Cr3+ ions at pH over 5 rarely found, because (Cr(OH)3)it is hardly soluble in water.
Chromium (VI) stable but are reduced to chromium (III) compounds under anaerobic conditions. The reaction is reversable. Chromium is floating as particles in water.
The LC50 value: in sea fish is between 7 and 400 ppm, for daphnia at 0.01-0.26 ppm, and for algae at 0.032-6.4 ppm.
Chromium (VI) in water hazard class 3, and very toxic.
Chromium phytotoxicity is undetermined. Concentrations between 500 to 6000 ppm in soils not harmfull for plants. Lime and or phosphate in soils decreases chromium. Dried soil contains 2-100 ppm of chromium. Its solubility in soil water is less than other toxic metals and so low plant uptake about 0.02-1 ppm chromium and may increase to 14 ppm. In mosses and lichens high concentrations can be found.
Chromium (VI) toxic for both plants and animals even low concentrations which is pH dependent. Chromium (VI) mobile in soils than chromium (III) compounds, and Chromium (VI) reduces to chromium (III) compounds within a short time. Soluble chromates converted to insoluble chromium (III) salts so uptake for plants decreases protecting the food chain from high chromium. Chromate mobility in soils depends on soil pH and soil absorption capacity, and on temperature. Chromium in agricultural soils is approximately 100 ppm.
Chromium has four stable isotopes and eight instable isotopes. The 51Cr, normally applied for diagnosis and have average degree of radioactivity.
What are the health effects of chromium in water?
The human body contains about 0.03 ppm of chromium and daily intake about 15-200 μg, and could be upto 1 mg. that is about 0.5-1%. The placenta is the organ with the highest chromium amounts.
Human body requirement of Trivalent chromium is essentially as a trace element. It removes glucose from blood, and is used in fat metabolism. Chromium deficiancy may cause diabetes symptoms.
Chromium (III) at recomended level do not shows to be toxic through food and drinking water. It may even improve health, and cure neuropathy and encephalopathy.
Hexavalent chromium has negative health impact and extreme toxicity. It causes allergic and asthmatic reactions, is carcinogenic. Hexavalent chromium is 1000 times toxic as compared to trivalent chromium. Hexavalent chromium exposes diarrhoea, stomach and intestinal bleedings, cramps, and liver and kidney damage and is mutagenic. Toxic effects may be transfer to children through the placenta.
Chromium (VI) oxide is a strong oxidant when dissolve form chromium acid which corrodes the organs and may cause cramps and paralysis due to high dose 1-2 g. Legal limit of 50 ppb chromium in drinking water.
In chromium industries illness may cause due to skin contact with chromates. Chromium trioxide dust uptake in the workplace may cause cancer, and damage the respirational tract.
Purification
Significant influence by drinking water quality. Normally a considerable ammount not found in groundwater and surface water. Specific removal in sewage water treatment is therefore unusual.
Chromium removal from water is ion exchangers and active carbon can be applied for this purpose.
it Precipitate as hydroxide, coagulation may not be a effective process to remove chromium(VI). Iron Sulphate can be used to reduce chromium(VI) to chromium III and can be removed but not usually used in drinking water preparation.
This is the end of Part One. Come back later for the next Part.
Comments
Post a Comment