Water Contaminants - Part 4
Water contaminants
Brief information
limits of contaminants for safe drinking water and Health effects
Part-4
14-Nitrogen (N) and waterNitrogen and water: reaction mechanisms, environmental impact and health effects
Nitrogen in seawater:
- about 0.5ppm as dissolved inorganic compounds and found approximately lower at the surface - - about 0.1ppb. River water: concentration varies but in general about 0.25ppm - Nitrogen mainly found in water as N2 and NO3 subject to the environmental condition and may occur as NO2, NH3, NH4, HNO2, NO2- HNO3
-Nitrogen as gas N2 found in coastal areas. As air contains 78% of nitrogen comes in contact with water in coastal areas usually higher in surface active current rather in deep water.
- In the Biological process Ammonium, Nitrates and Nitrites play an important role. Nitrogen estimation count organic and inorganic compounds as total Nitrogen like in Kjeldahl Nitrogen test showing total value as TKN (including organic Nitrogen, Ammonium Nitrogen(TKN = Org
-N +NH4)mg/l mostly found in wastewater.
In Biological wastewater treatment it occurs as oxidised Nitrite.
Chemically nitrogen does not react but just dissolve in water.
The solubility of nitrogen and nitrogen compounds
Nitrogen solubility is about 20mg/l at 20oC and at 1 bar pressure.
Nitrogen oxide solubility is 12g/l.
Nitriloacetate solubility: 640g/l.
Nitrates and ammonia dissolve readily in water.
Nitrogen chloride is insoluble in water.
Nitrogen end up through agricultural process and in water. Nitrogen compounds in water through fertilizer and nitrates also as ammonia, ammonium urea and amines. most widely used fertilizers are NaNO3(sodium nitrate), NH4NO3(Ammonium Nitrate).25-30% fertilizer added to crops and residual added to ground/surface water through the soil as Nitrates are water soluble. Organic fertilizer contains nitrogen as proteins, urea or amines have different absorption techniques. Some pesticides added to the farm also contain Nitrogen.
For industrial purposes, it is applied for ammonia synthesis by Harer Bosch process. Some other compounds like nitrous oxide used in anaesthetics, in the production of nitric acid, urea, hydrazine and amines. Some nitrogen compounds also produced as by-products of colouring and synthetic agent production.
Liquid nitrogen used to freeze food and deep freezing samples and agent for superconductor and ceramic production.
For semiconductor production, it is used as a protective gas in welding and spray for fire extinguishers. As N2O4 it is rocket fuel oxidation. also used as explosive applied in mines.
Nitrogen found in domestic wastewater and concentration depends on protein usage. Organic nitrogen compounds like found in urea finally forming ammonium salts. About 3% nitrates and nitrites found in domestic wastewater.In wastewater treatment first to decompose ammonium and nitrates.
Nitrates and nitirites used as a food additive for red colour meat and to save toxin formation. In detergents NTA(nitriloacetate) is used to replace phosphate. Soil from landfills is the sources of nitrogen to end up in groundwater. Nitrogen cycle will explain the occurrence of nitrogen in the soil.
Effects of nitrogen in water?
Nitrogen as dietary for all organism constitute all proteins and nucleic acid. In plant it is essential
and 75% of the plant is of Nitrogen and found a large amount in the air. Nitrogen bound and convert like nitrate and carried out by bacteria which convert ammonia and ammonium to nitrate and nitrite releasing energy as stock in soil may apply in plants.
By applying fertilizers nitrogen increase in plants like in spinach accumulate nitrogen compounds. when fertilizer used outside the growing season effectively negative to the environment and ultimately end up in soil adding to groundwater and some spread as No2.
In precipitation nitric acid together with sulphuric acid caused acid rain effects negatively in crops and soils.
Nitrogen is an essential part of protein and the large amount found in animal tissue but no effect on warm-blooded organisms. High nitrogen in air may cause asphyxiation due to the reduction of oxygen.
In water, it is not harmful and causes no environmental problem. Nitrates, Nitrites and ammonia is dietary for plankton causing lowering at the surface than in deep water. when surface nitrogen increases plankton production also increases ultimately algal blooms. Excessive nitrate may result in eutrophication meaning an excess nutrient causing a lack of oxygen resulting death of fishes.Nitrogen could not control algal growth but phosphorus can control water bodies so phosphorus is the main cause of algal spreading on surface water. Reduction Oxygen in surface reducing nitrogen to nitrous oxide called as denitrification causing oxygen release when oxygen supplies reduces to zero. Some time nitrates biologically reduce to ammonia and ammonium compounds reduces oxygen concentration because of oxidizing nitrite to nitrate. Even less ammonia may be toxic to fish.
In water, nitrification is an important to process meaning ammonia oxidation to Nitrite and nitrate. during this process nitrite decreases which is good for higher plants as at low pH nitrite is toxic.
Nitrogen oxides from the atmosphere when dissolving in water forming nitric acid reduce nitrogen oxide concentration in the atmosphere. PAN (Peroxy Acetyl Nitrate) compounds form from terrestrial pollution and transfer to the troposphere and in oceans and finally decompose to nitrogen oxides.
Toxic nitrogen compounds like NTA complexed with heavy metals can disturb metabolism. Rates kidney can be damaged at a concentration above 14mh/kg body weight. LD50 value is 1.5g/kg for rats, 0.75g/kg for rhesus monkey. it may cause chromosome defects in vitro system. for the fishes, the concentration about 10mg/l(48 h) is non-toxic.
Nitrogen has two stable and six unstable isotopes
Health effects of nitrogen in water:
The human body has about 2.6% nitrogen as proteins and nucleic acid. It is a dietary requirement, the main constituent of air we breath, an increase of nitrogen in air may cause asphyxiation or due to a low concentration of oxygen in the air.
Nitrogen absorb as proteins which can not be stored but just convert into energy. Nitrogen excreted from kidney as urea, also release fro skin and intestinal tract. The factor to convert nitrogen to protein is 6.25.
Nitrates generally not toxic but when high concentration, the body convert nitrate to nitrite which is a toxic salt which disturbs blood oxygen transportation and causing to convert Haemoglobin to methemoglobin. this causes nausea and stomach aches. For null it is extremely null and causes oxygen deprivation.
As per EPA recommendation for null being for nitrates is 10mg/l, and for nitrite is 1.00mg/l.
From protein, null food nitrites and amines may form nitrosamines which are carcinogenic and can be prevented by reducing the null food and anti-oxidant property of vitamin C.
Toxic nitrogen compounds as PAN compounds are 50 times more toxic then normal nitrogen compounds converted from (nitriles and nitrilo Compounds). NTA is not absorbed in the stomach because of heavy metal complex however disturb metabolism.
Nitrogen oxide in the air is more significant than in water causing breathing problem. Nitrogen hydrogen acid fumes may cause irritation, heart problem and null.
Purification technologies:
The first two steps of treatment that are a reation and pH adjustment along null some chemicals may remove about 50% of nitrogen and further treatment null lme and HOCl and finally by biological nitrogen removal by nitrification and denitrification carried out by null organisms.
Nitrification is the process of ammonium oxidation by protein decomposition by bacteria to convert into nitrite and then nitrates which need oxygen by aeration for a sufficient period. the reaction is as under:
2 NH4+ + 3 O2 -> 2 NO2- + 2 H2O + 4 H+ - by Nitrosomonas
2 NO2- + O2 -> 2 NO3- - by nitrobacter
In denitrification bacteria decomposes nitrates to nitrogen which do not require aeration in presence of carbon to speed up the decomposition process and finally released into the air. the reaction as follows:
6 NO3- + 5 CH3OH -> 3 N2 + 5 CO2 + 7 H2O + 6 OH-
In wastewater treatment both process nitrification needing oxygen and denitrification in which no need of oxygen applied as the third step removing about 90% of nitrogen.
In some countries like Brazil the third step water hyacinths used for purification removing both nitrogen and phosphorous from water using helophyte filters for water purification.
Ammonia null by stripping by means of air or steam gasifying.
Some other compounds usually in small amount by the null method for null NTA can be decomposed in aeration tanks. Nitro null cannot be decomposed
null ionic nitrogen compounds like NO3-, NO2-, and NH4+, and amines can be removed by ion exchange.
15- Oxygen (O) and water
The most common element on earth is Oxygen found as O2, O3(ozone) and in may compounds including water molecule and as dissolved oxygen in the water. oxygen content in seawater is 85.7%
Oxygen null not react with water but dissolved in water and act like oxydator see as under:
O2 + 2 H2O + 4 e- -> 4 OH-
Organic matter oxidizes organic null by the null process by the different biological process for each compound by electron balance, see as under:
Fe2+ + 0,25 O2 -> Fe(OH)3 + 2,5 H+
Mn2+ + O2 -> MnO2 + 2 H+
NH4+ + 2 O2 -> NO3- + 6 H+
CH4 + 2 O2 -> CO2 + 4 H+
In the above reactions, ammonium and methane required for oxidation large amount of oxygen forming a higher or lower amount of acid, normally acid in water react with HCO3 to form CO2.
Oxygen reacts and oxidize almost all elements except helium, argon and krypton but null of compounds react with water.
At 25oC and 1 bar pressure solubility of oxygen in water is 40 mg/l. In the atmosphere, the null pressure of oxygen is 0.2 atm, both factors cause dissolution in water when contact with air. Oxygen solubility depends on temperature and amount of dissolved solids in water and decrease at higher level and increase at a lower level. while oxygen solubility in null than in seawater exceeds by 1-3 mg/l depending on temperature.
In solubility saturation is pressure dependent and so lower in mountainous areas than in lower areas like low land. When air comes in contact with water, its oxygen dissolves in water. Oxygen is commercially used 100 million tons annually, 55% in steel production, 25% in chemical industries, other use is in hospitals, staring missiles and in slicing metal. Ethylene oxide is applied as an antifreeze and polyester. Being highly reactive used to breakdown hazardous substances. Also applied as bleaching. Ozone compound applied for disinfection in drinking water
Environmental effects of oxygen in the water
As an oxidizing agent occurs during the fire, within an organism, bacterial destruction and metal conversion.
Oxygen is very essential for plants and animals as it is apart of DNA and all other biologically concerned. About 200 cm3 oxygen dissolve in blood in the lungs bound with iron to produce Haemoglobin and reserve energy for muscles activity and heat production. In this mechanism carbon dioxide releasing to pick up by plants where the plants produce oxygen during photosynthesis. Plants contain 4.1 to 4.4 % oxygen.
Water stability and survival of water organism depend on dissolved Oxygen. In water treatment system organic substances decompose by null organisms in presence of dissolved oxygen. Oxygen application can be indicated by BOD (biological Oxygen demand) and COD (chemical oxygen demand). Organic pollution influence water organism negatively reducing BOD same as inthermal pollution because of solubility decrease in warm water and consequently cooling water discharge on surface water.
Oxygen concentration decreases in deep water and can be called as anaerobic. Seasonal influence on oxygen in lakes due to temperature variation in the surface layer than deeper water. In winter temperature almost null in the upper and lower water layer having the same oxygen but in summer it is different because of different temperature in upper and lower layers due to different solubility in different temperatures. null and plants null oppositely having high oxygen amount in warmer water resulting null oxygen meaning to have a null condition for null organism making to die the plants quickly happening in the surface layer of water. so organic matter null in the null layer and remains as in sediments and may cause oxygen deficits from decomposition until equilibrium established and the problem may be solved
Pure Oxygen normally not released which could be hazardous to an aerobic organism, theoretically such concentration can be achievable but partial pressure differs per species. Oxygen atom found in toxic organic and inorganic compounds. Toxic compounds like hyper oxides and peroxide, some are toxic in low oxygen in water because of breathing of organism and absorb substances more rapidly and so for anaerobic organism high oxygen concentration are toxic.
The function of Ozone in the stratosphere as a protective layer reflects solar UV radiation as it is the most important that without Ozone Layer it is impossible to have life on earth even many plant species are susceptible to high ozone concentration in the air just growth limitations.
Oxygen has 3 stable and five unstable isotopes.
Health effects of oxygen in the water.
Total Oxygen in the human body is about 60% /body weight it may vary because of water molecules in the body.
Human and other organisms absorb oxygen through lungs and transfer to other organs through the bloodstream by fine capillaries through blood bound to haemoglobin subsequently stored in muscles in myoglobin. Oxygen in drinking water helps as protective coating formation in metal pipes for water transportation and need about 6 to 8 mgll
Oxygen as radicals causes derivative diseases like cancer and heart diseases.
Low concentration of oxygen like 3% may cause death by asphyxiation, Less than 7% may lose consciousness. Excess oxygen may be lethal, Baby's receiving excessive oxygen in incubators grow blind.
Ozne is a toxic form of oxygen may damage the lungs and may include hyper oxides, peroxides and hydroxyl radicals
Purification technologies:
Oxygen removal may need for water pipes to protect from corrosion. It can be removed by some physical-chemical process and ion exchange. the basic principle is the reaction between hydrogen and oxygen as 2H2 + O2 -> 2H2O. the reaction may be catalysed by several compounds to speed up the reaction. Palladium ion resin reduces water oxygen when enough amount of hydrogen. Hydrazine instead of hydrogen can be used also as O2 + N2H4 ->N2 +2H2O.
Thermal degasification can be used for oxygen removal and can be applied in some cases but not every occasion. The pressure degasifier can be used under little overpressure (up to 5 bar) or vacuum degasification under slight under pressure. While the water enrichment by oxygen can be done various methods like Pollutant removal, ratification aeration, by surface aeration, by inserting air through pressure filters, by increasing water flow through centuries, aeration with our oxygen, by aeration in purification plants etc.
Oxygen has cleansing effects and essential for a microorganism and oxidizes compounds as indicated by BOD (Biological oxygen demand) or COD ( chemical oxygen demand).
BOD indicates oxygen concentration used by the microorganism in 5 days in aerobic condition to convert organic matter to carbon dioxide, water and biomass as indicates by mg O2/l of wastewater. This value multiplies by wastewater volume gives an amount of hazardous mater. BOD5/unit of time called BOD load, excluding the hardly decomposable due to the short of time.
COD is the amount of oxygen mg/l of wastewater required for oxidizable matter for both easily or hardly decomposable compounds like organic chlorine compounds which exceed BOD value.
Ozone can be used for purification and disinfection of water for drinking, in swimming pool. It is stronger disinfectant than chlorine but unstable and convert back to oxygen favouring for drinking water because excess ozone may harmful for lungs.
16. Potassium (K) and water
Potassium and water: health effects
Potassium in seawater is about 400 ppm mostly settle in sediments. Natural concentration of potassium in seawater is about 4.5 to 10 - 5 g/l. Potassium in river water about 2 - 3 ppm.Granite which a calcium-rich mineral contain 2.5% potassium. This large difference is because of potassium concentration in oceanic basalts. Granite is a calcium-rich mineral containing 2.5% potassium and present in water as K ions.
40k is a radioactive potassium isotope.
40K is a naturally abundant radioactive potassium isotope. Seawater contains a natural concentration of about 4.5. 10-5 g/L.
Potassium rapidly react with water forming potassium hydroxide and hydrgen gas as under:
2K (s) + 2H2O (l) -> 2KOH (aq) + H2 (g)
Potassium reaction is exothermic releasing hydrogen and reacting with oxygen to ignite. potassium burn with a purple flame
As potassium placed in between Rubidium and Sodium in periodic table so the reaction of potassium is slower than Rubidium and faster than Sodium.
The solubility of potassium and its compounds
The reaction of potassium with water already explained above. Potassium compounds mostly water soluble like: potassium dichromate solubility = 115g/l, Potassium Permanganate76g/l, Potassium Iodide = 92g/l and also goes up to 1480 g in one litre of water.
Potassium in water
Potassium present in various minerals and dissolution depends on various weathering effects like felspar(orthoclase and microcline) are slow production of compounds when chlorine minerals(carnalite and sylvite are faster. clay minerals containing potassium end up into seawater through natural process and ultimately settle in sediments.
Potassium extracted from potassium chloride do not serve for many purposes because of its extensive reacting power and is applied in alloy and organic synthesis.
Many potassium compounds mainly potassium nitrate is used in synthetic fertilizer 95%. Potassium salt and a mixture of calcium and magnesium are regularly applied. The regeneration releases hazardous wastewater when discharge on surface water and is difficult to purify.
Potassium used in the glass industry to make the product stronger and solid like TV screens. Some other compounds also used in liquid soap, medicines or infusion, in photography or tanning. Potassium chlorate used in matches and fireworks and for potassium nitrate powder. Potassium alum is also used for making paper glue and as a filler for synthetic rubber.
Potassium compounds like potassium hydroxide and nitrates are few of the most reactive basic chemical compounds like potassium hydroxide form caustic potash and used in detergents, softners, green soap, oil desulphurization and carbon dioxide absorbers.
Some other compounds like potassium iodide for measurement of waste oxidation, potassium dichromate for organic matter oxidation capacity measurement which is used in soil science and wastewater treatment, potassium dicyano-aureate which is extremely toxic gold compound and water-soluble compounds used for gilding, and end up in wastewater treatment through urine. In the dry region, potassium compounds may increase raining. it releases below the cloud from planes, rises up to increase the amount of moist in clouds causing harder rain.
Potassium releasing from domestic waste usually high indicates the toxic compounds in groundwater.
Effects of potassium in water:
Potassium is a dietary requirement for any organism especially for bacteria's nerve functions. Also important for plant growth limits. From dead plants and animals potassium bound to clay minerals in soils before dissolving in water and taken up plant again. Potassium used as fertilizer in the soil. on average value in plants vary from 0.1 - 6.8%. Potassium in mosquito larvae between 0.5 to 0.6%, beetles contain 0.6 to 0.9% as dry mass. Potassium salts are harmful to plant cell because of high osmotic activity.
In water, potassium is a low hazardous but rapidly spread. Potassium toxicity is usually due to other components like cyanide in potassium cyanide.
For rates LD50 value is 5mg/kg. For potassium bromide this is 321mg/kg, for potassium fluoride 245mg/kg. LD50 value for water organism 132mg/l for fish, 1.16mg/l for daphnia.
Potassium natural isotopes are 40K which is radioactive and is suspected cause of animal gene modification. it is not in a toxicity class due to its natural origin. potassium has twelve unstable isotopes.
Health effects of potassium in water.
Potassium is a dietary requirement for human being and 1 - 6g per day at a requirement of 2 -3.5 g/day. Total amount in the human body is 110 to 140 g depending on muscles mass. Potassium occurs in muscle's red blood cells and brain tissue.
Sodium present as intracellular fluid while potassium present in the cell preserving the osmotic pressure. Potassium in the cell and in plasma is 27:1 and regulate by sodium-potassium pumps.
Potassium vital role in nerve stimulus, muscle contraction, blood pressure regulation and protein dissolution, protect heart and arteries preventing cardiovascular diseases. Sodium and potassium relation normally 1:16 which when 3:1 which prevent high sodium uptake.
Normally potassium shortage is rare but it occurs may cause depression, muscular weakness, heart disorder and confusion. Potassium loss may cause chronic diarrhoea or kidney disease as a kidney is a regulator for potassium physical balance. Due to kidneys lake of function potassium must have limited intake to prevent greater losses.
Caustic potash corrosion occurs when skin contact with potassium metal which is more hazardous than acid corrosion as it continues unlimitedly. The drops of caustic potash are more damaging to the eye.
Potassium compounds are harmful to intake, Potassium chloride high dose interferes nerve impulses which also interferes body function including the heart. Potassium alum intake as low as 2g may cause stomach problem. Potassium carbonate intake may be harmful above 15g same as potassium tartrate at 1g, and cyanide at only 50 mg. Potassium dichromate between 6 - 8 g, potassium nitrate is severely toxic may cause death, potassium hydroxide between 10 - 12ml in 15% caustic may be lethal. Potassium permanganate is used for bleaching and disinfection and lethal at 5 - 8g.
Purification technologies
Reverse Osmosis is usually used to remove Potassium from the water.
In water purification, potassium permanganate is used for oxidation of waterborne compounds, for removal of iron or manganese and disinfection. Potassium permanganate is used to determine the oxidation capacity of organic matter in water and generally exceeds BOD. Potassium dichromate is used to determine COD.
This is the end of Part Four. Come back later for the next Part.
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References: taken from Lenntech
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