Pollutants exhausts from automobiles
Automobiles used in our country are
a) Two wheelers and three wheelers, powered by two stroke petrol engines.
b) Passenger cars, powered by four stroke petrol engines.
c) Trucks and buses, powered by four stroke diesel engines.
The extent of pollution by these automobiles depends upon the enzine design, fuel consumption, operating condition. The emission from petrol engines are classified as follows:
A. Exhaust emissions
Theses are mostly comprised of CO, NOX, particulars containing lead compounds and unburned hydrocarbons. We can control the emission by the following ways
i. Modification of engine design
ii. Modification of operating conditions
iii. Treatment of exhaust gases.
iv. Modification of alternation of fuels.
B. Crank case emissions
It mostly contains hydrocarbons. The quality of blow depends on engine design, operating condition. This emission can be constituted by the following ways
i. By installing positive crank case ventilation system.
C. Evaporation emissions
It is estimated that an average evaporation emission of hydrocarbons from a passenger car is about 20 kg per year. Various methods to control evaporation emission are given below:
a. Stone the fuel vapour in crank case.
b. Modifying fuel by replacing C4 and C5 by corresponding paraffinic hydrocarbons.
c. Introducing suitable mechanical device.
Wednesday, August 24, 2011
Ozone (O3), Peroxy-acyl nitrile(PAN) and Photochemical smog
Ozone (O3), Peroxy-acyl nitrile(PAN) and Photochemical smog
Characteristics of Ozone (O3), Peroxy-acyl nitrile(PAN) and Photochemical smog
a) Pale blue gas.
b) Fairly water soluble, unstable and sweetish odour.
c) Very reactive oxidizing agent.
d) Capable of combining with many organic compounds in cells and tissues as well as rubber and other materials.
e) Ozone (O3) and Peroxy-acyl nitrile(PAN) are harmful to animals and humans.
Biochemical effects of Ozone (O3), Peroxy-acyl nitrile(PAN) and Photochemical smog
a) Oxidize cellular constituents.
b) Produce free radicals which are capable of producing toxic compounds.
c) Damage the DNA and reduce the genetic power.
d) Both Ozone (O3) and Photochemical smog causes eye irritation and respiratory tract.
e) Causing damage of lung capillaries.
f) Ozone may inhibit the activity of some enzyme involved in synthesis of cellulose and lipids in plants.
g) The Sulphur containing amino acid, example: Cystine are strongly attacked by PAN.
Characteristics of Ozone (O3), Peroxy-acyl nitrile(PAN) and Photochemical smog
a) Pale blue gas.
b) Fairly water soluble, unstable and sweetish odour.
c) Very reactive oxidizing agent.
d) Capable of combining with many organic compounds in cells and tissues as well as rubber and other materials.
e) Ozone (O3) and Peroxy-acyl nitrile(PAN) are harmful to animals and humans.
Biochemical effects of Ozone (O3), Peroxy-acyl nitrile(PAN) and Photochemical smog
a) Oxidize cellular constituents.
b) Produce free radicals which are capable of producing toxic compounds.
c) Damage the DNA and reduce the genetic power.
d) Both Ozone (O3) and Photochemical smog causes eye irritation and respiratory tract.
e) Causing damage of lung capillaries.
f) Ozone may inhibit the activity of some enzyme involved in synthesis of cellulose and lipids in plants.
g) The Sulphur containing amino acid, example: Cystine are strongly attacked by PAN.
Oxides of Sulphur
Oxides of Sulphur ( SOX)
Sources of Oxides of Sulphur ( SOX)
a) Combustion of coal
b) Combustion of petroleum products.
c) Burning of refuse
d) Oil refining
e) From power house
f) Sulphuric acid plant
g) Metallurgical operation.
h) Domestic burning of fuel.
Characterisrics of Oxides of Sulphur ( SOX)
a) Comprises of SO2 is 97 to 99 % and SO3 is 3 to 1 %.
b) SO2 is colourless, heavy, water soluble gas with pungent smell and irritating odour.
c) SO2 is rapidly diffusing, acid forming, oxidizing agent.
d) React with water forming H2SO3 and H2SO4 both of which can react with organic matter, metals and other materials.
Biochemical effects of Oxides of Sulphur ( SOX)
a) Absorbs quickly and irritates the upper respiratory tract.
b) Reacts with cellular constituent, example is enzyme.
c) The sulphuric acid forms lowers pH, which impairs enzymatic funtions and destroys various functional molecules.
d) Lung clearance and impaired pulmonary function are occurred.
Control of Oxides of Sulphur ( SOX)
a) Absorb SO2 is from the air.
b) Separate Sulphur from fuel.
c) Minimize the use of Sulphur fuel.
d) Use of natural gas instead of Sulphur fuel.
Sources of Oxides of Sulphur ( SOX)
a) Combustion of coal
b) Combustion of petroleum products.
c) Burning of refuse
d) Oil refining
e) From power house
f) Sulphuric acid plant
g) Metallurgical operation.
h) Domestic burning of fuel.
Characterisrics of Oxides of Sulphur ( SOX)
a) Comprises of SO2 is 97 to 99 % and SO3 is 3 to 1 %.
b) SO2 is colourless, heavy, water soluble gas with pungent smell and irritating odour.
c) SO2 is rapidly diffusing, acid forming, oxidizing agent.
d) React with water forming H2SO3 and H2SO4 both of which can react with organic matter, metals and other materials.
Biochemical effects of Oxides of Sulphur ( SOX)
a) Absorbs quickly and irritates the upper respiratory tract.
b) Reacts with cellular constituent, example is enzyme.
c) The sulphuric acid forms lowers pH, which impairs enzymatic funtions and destroys various functional molecules.
d) Lung clearance and impaired pulmonary function are occurred.
Control of Oxides of Sulphur ( SOX)
a) Absorb SO2 is from the air.
b) Separate Sulphur from fuel.
c) Minimize the use of Sulphur fuel.
d) Use of natural gas instead of Sulphur fuel.
Oxides of Nitrogen
Oxides of Nitrogen (NOX)
Sources
a) Automobile exhausts
b) Coal fire, gas fire furnace
c) Various boiler, power plant
d) Explosive industry
e) Fertilizer industry
f) Manufacturer of nitric acid
g) Firing of refuse
Characteristics of Oxides of Nitrogen
a) It comprises of NO, NO2, N2O
b) NO is colorless gas, slightly soluble in water.
c) NO2 is radish brown
d) N2O is soluble in water
e) NO2 is a oxidizing agent and form nitric acid by reaction in water.
f) Capable of reaction with all metal or organic compounds.
g) Involve in formation of ozone in atmosphere.
Biochemical effects of Oxides of Nitrogen
a) It can oxidize cellular lipids.
b) They can form bonds with hemoglobin.
c) They can reduce the efficiency of oxygen transport.
d) They can reduce destroy the catalytic power of enzyme.
e) No may be bonded with hemoglobin and form additional compound which is harmful for the body.
Effects of Oxides of Nitrogen on plants
a) Higher concentration of NO2 may be cause of damage of the leaves of plants.
b) May damage the tissue of the plants.
c) NO2 is highly destructive to plant and damage the vegetation power.
Control of Oxides of Nitrogen
a) Moderate a system to absorb the automobile exhausts.
b) Lowering the temperature in fertilizer industry.
c) Catalytic decomposition.
d) Reaction between NO and NO2.
e) Control of unwanted firing.
Sources
a) Automobile exhausts
b) Coal fire, gas fire furnace
c) Various boiler, power plant
d) Explosive industry
e) Fertilizer industry
f) Manufacturer of nitric acid
g) Firing of refuse
Characteristics of Oxides of Nitrogen
a) It comprises of NO, NO2, N2O
b) NO is colorless gas, slightly soluble in water.
c) NO2 is radish brown
d) N2O is soluble in water
e) NO2 is a oxidizing agent and form nitric acid by reaction in water.
f) Capable of reaction with all metal or organic compounds.
g) Involve in formation of ozone in atmosphere.
Biochemical effects of Oxides of Nitrogen
a) It can oxidize cellular lipids.
b) They can form bonds with hemoglobin.
c) They can reduce the efficiency of oxygen transport.
d) They can reduce destroy the catalytic power of enzyme.
e) No may be bonded with hemoglobin and form additional compound which is harmful for the body.
Effects of Oxides of Nitrogen on plants
a) Higher concentration of NO2 may be cause of damage of the leaves of plants.
b) May damage the tissue of the plants.
c) NO2 is highly destructive to plant and damage the vegetation power.
Control of Oxides of Nitrogen
a) Moderate a system to absorb the automobile exhausts.
b) Lowering the temperature in fertilizer industry.
c) Catalytic decomposition.
d) Reaction between NO and NO2.
e) Control of unwanted firing.
Friday, August 19, 2011
Air Pollution and Air Pollutants
Air Pollution
Air Pollution may be defined as the presence in the outer atmosphere of one or more contaminants or pollutants or combination of those substances in such quantities and of such duration as may be or may tend to be injuries to human, plant or animal life or property.
Classification of air pollutants
The air pollutants may be classified in different ways as follows
1. According to Origin
a) Primary pollutants: Directly emitted into the atmosphere. Example: CO, NO2, SO2 and hydrocarbons.
b) Secondary pollutants : divided from the primary pollutants due to chemical or photo-chemical reaction. Example: Ozone, PAN (0peroxy acyl nitrate), Photochemical smog.
2. According to chemical composition:
a) Organic pollutants: Example: Hydrocarbons, aldehydes, ketones, amines, alcohols.
b) Inorganic pollutants: Example: Carbon compounds( CO and Carbonates), Nitrogen Compounds(NOX, NH3), Halogen Compounds( HF, HCl), Oxidising agents( O3)
3. According to state of matter:
a) Gaseous pollutants: Get mixed with the air and do not settle out. Example: CO, NOX, SO2.
b) Particulate pollutants: Comprise of finely divided solids or liquids and often exist in colloid state as aerosols. Example: Smoke, fumes, dust, mist, fog.
Air Pollution may be defined as the presence in the outer atmosphere of one or more contaminants or pollutants or combination of those substances in such quantities and of such duration as may be or may tend to be injuries to human, plant or animal life or property.
Classification of air pollutants
The air pollutants may be classified in different ways as follows
1. According to Origin
a) Primary pollutants: Directly emitted into the atmosphere. Example: CO, NO2, SO2 and hydrocarbons.
b) Secondary pollutants : divided from the primary pollutants due to chemical or photo-chemical reaction. Example: Ozone, PAN (0peroxy acyl nitrate), Photochemical smog.
2. According to chemical composition:
a) Organic pollutants: Example: Hydrocarbons, aldehydes, ketones, amines, alcohols.
b) Inorganic pollutants: Example: Carbon compounds( CO and Carbonates), Nitrogen Compounds(NOX, NH3), Halogen Compounds( HF, HCl), Oxidising agents( O3)
3. According to state of matter:
a) Gaseous pollutants: Get mixed with the air and do not settle out. Example: CO, NOX, SO2.
b) Particulate pollutants: Comprise of finely divided solids or liquids and often exist in colloid state as aerosols. Example: Smoke, fumes, dust, mist, fog.
Carcinogen, Pesticides and Bio-warfare Agent
Carcinogen
The term carcinogen means a group of chemicals which cause cancer in animal and human. The carcinogens affect DNA, preventing it from giving the necessary direction for the synthesis of substances which control the cell growth.
Carcinogens to which workers should not be exposed. Some compounds:
1. 4-nitro phenyl
Uses: Chemical analysis
Hazards: may cause blader cancer.
2. α-napthyl amine
Uses:Antioxident, dye manufacturing, colour, film manufacter
Hazards: may cause blader cancer.
3. β –napthyl amine
Uses: dye manufacturing, reagent.
Hazards: May cause bladder cancer.
4. benzidine
Uses: manufactur of Dye, Rubber, plstic
Hazards:it may cause bladder.
5. 3,3 dichlorobenzidine:
Uses: dye manufacturer
Hazards: known carcinogen
6. veinyl chloride:
Uses: PVC manufacture
Hazards: liver cancer
7. ethylene dichloride :
Uses: industrial solvent, gasoline additive
Hazards: lung cancer
Biochemical Effects of Pesticides
Biochemical processes constitute the major mechanism by which pesticides in the environment are degraded and detoxified.
Among the pesticides, the biological action of DDT on the environment has been most extensively studied. The central nervous system is the target of DDT, like many other insecticides. DDT dissolves in lipid (fat) tissue and accumulates in the fatty membrane surrounding nerve cells. The net result is disruption of the central nervous system killing the target insect.
While DDT is fairly insoluble and persist in the environment, the other groups organophosphates and carbamates degrades quite rapidly in the environment. The later react with oxygen (O2) and water (H2O) undergoes decomposition within a few days in the environment.
DDT accumulates in the food chain as
Plankton (0.04 ppm DDT) >> Fish (0.17 to o.27 DDT) >> Fish eating birds (3.1 to 75.5 ppm)
Fish (0.17 to o.27 DDT) >> Clams 0.42 ppm DDT >> Plankton (0.04 ppm DDT)
Bio-warfare Agent
The bio-warfare agent which are harmful to human being are called bio-warfare agent.
1. Anthrax
Definition: bacteria in spore form not contagious
Attack: inhalation, ingestion, skin abrasion
Symptoms: flue like symptoms lead to breathing problem
Treatment: treatment by antibiotics or pre-vaccine
2. Plague
Definition: agent is rodents, contagious
Attack: through aerosol cans
Symptoms: fever, headaches and weakness
Duration of Death: 2-4 days
Treatment: Treatment by antibiotics
3. Small pox
Definition: it is deadly and highly contigious
Attack: through aerosol cans
Symptoms: fever, fatigue and body aches
Duration of Death: first 2 weeks.
Treatment: vaccine
4. Chlorine
Definition: green yellow pungent smelling gas
The term carcinogen means a group of chemicals which cause cancer in animal and human. The carcinogens affect DNA, preventing it from giving the necessary direction for the synthesis of substances which control the cell growth.
Carcinogens to which workers should not be exposed. Some compounds:
1. 4-nitro phenyl
Uses: Chemical analysis
Hazards: may cause blader cancer.
2. α-napthyl amine
Uses:Antioxident, dye manufacturing, colour, film manufacter
Hazards: may cause blader cancer.
3. β –napthyl amine
Uses: dye manufacturing, reagent.
Hazards: May cause bladder cancer.
4. benzidine
Uses: manufactur of Dye, Rubber, plstic
Hazards:it may cause bladder.
5. 3,3 dichlorobenzidine:
Uses: dye manufacturer
Hazards: known carcinogen
6. veinyl chloride:
Uses: PVC manufacture
Hazards: liver cancer
7. ethylene dichloride :
Uses: industrial solvent, gasoline additive
Hazards: lung cancer
Biochemical Effects of Pesticides
Biochemical processes constitute the major mechanism by which pesticides in the environment are degraded and detoxified.
Among the pesticides, the biological action of DDT on the environment has been most extensively studied. The central nervous system is the target of DDT, like many other insecticides. DDT dissolves in lipid (fat) tissue and accumulates in the fatty membrane surrounding nerve cells. The net result is disruption of the central nervous system killing the target insect.
While DDT is fairly insoluble and persist in the environment, the other groups organophosphates and carbamates degrades quite rapidly in the environment. The later react with oxygen (O2) and water (H2O) undergoes decomposition within a few days in the environment.
DDT accumulates in the food chain as
Plankton (0.04 ppm DDT) >> Fish (0.17 to o.27 DDT) >> Fish eating birds (3.1 to 75.5 ppm)
Fish (0.17 to o.27 DDT) >> Clams 0.42 ppm DDT >> Plankton (0.04 ppm DDT)
Bio-warfare Agent
The bio-warfare agent which are harmful to human being are called bio-warfare agent.
1. Anthrax
Definition: bacteria in spore form not contagious
Attack: inhalation, ingestion, skin abrasion
Symptoms: flue like symptoms lead to breathing problem
Treatment: treatment by antibiotics or pre-vaccine
2. Plague
Definition: agent is rodents, contagious
Attack: through aerosol cans
Symptoms: fever, headaches and weakness
Duration of Death: 2-4 days
Treatment: Treatment by antibiotics
3. Small pox
Definition: it is deadly and highly contigious
Attack: through aerosol cans
Symptoms: fever, fatigue and body aches
Duration of Death: first 2 weeks.
Treatment: vaccine
4. Chlorine
Definition: green yellow pungent smelling gas
Wednesday, August 17, 2011
Toxicity of Mercury and Cyanide
Sources and Toxicity of Mercury (Hg)
Sources: Industrial mining, waste, pesticides, coal etc.
The Toxicity of Mercury depends on its chemical species as shown below
1) Properties of Mercury (Hg)
o Elemental Hg is fairly inert and non-toxic.
o Vapour highly toxic when inhailed
o If swallowed, it excreted without serious damage.
2) Mercuous ion(Hg2+)
o Insoluble as chloride
o Low toxicity
3) Mercuric ion(Hg3+)
o Toxic but not across biological membrane
o It attacks the sulphur containing amino acid of protein.
4) Organomercurials
o Highly toxic
o Partially causes irreversible nerve and brain damage.
o Easily transported to the biological membrane.
o Stored in flat tissue.
5) Diorganomercurials
o Low toxic
o Can be converted into Organomercurials.
6) Mercuric Sulphide (HgS): highly insoluble and non-toxic.
Biochemical effects of Cyanides
Cyanides occurs in seeds of fruits such as apples, apricots, cherries, peaches and plums. Cyanide in the plant is bonded to glycoside(sugar) called amygdalin and is released by enzymatic or acidic hydrolysis. Cyanide enters the environment from many sources. HCN is employed as a fumigating agent to destroy rodents in grain bins, building in electroplating and metal cleaning industry.
Cyanide exerts its toxic action by inhibiting oxidative enzymes from mediating the process by which oxygen is utilized to complete the production of ATP n the mitochondria
In the first step cyanide bind to ferricoytochrome oxydase. The important products are the ATP
Step 1: Fe (3)-oxide + glucose >> Fe (2)-oxide
Step 2: Fe (2)-oxide + 2H+ + 1/2O2 >> Fe(3) + H2O + ADP/ATP
Cyanide interferes with step 1 above by forming a bond with Fe(3)-oxide, which is thereby inactivated so that the reaction in step 2, the energy producing process is prevented.
Biochemical Effects of Arsenic, Cadmium and Lead
Biochemical Effects of Arsenic
Arsenic commonly occur in insecticides , fungicides and herbicides. Arsenic exerts its toxic action by attacking SH groups of an enzyme, thereby inhibiting action
SH(Enzyme)SH + O2As(O) >> S (Enzyme)S-As-O + 2OH-
The enzymes which generate cellular energy in the citric acid cycle are adversely affected. The inhibitory action is based on inactivation of pyruvate dehydrogenase by complexation with As, were by generation of ATP is prevented.
A more important step is ATP generation is the enzymatic synthesis of 1,3 diphosphoglycerate from glyceraldehyde 3-phosphate . Arsenic interacts by producing 1-arseno-3-phosphoglycerate instead of 1, 3 diphosphoglycerate.
Biochemical Effects of Cadmium
Cadmium occurs in nature in association of zinc minerals. The biochemical effects of cadmium are
a) At high levels cadmium causes kidney problems, aneamia and bone mammrow disorder.
b) The major portion of cadmium ingested our body is trapped in the kidneys and eliminated
c) Small portion is bound most effectively by the body protein, present in the kidney and rest is stored in the body.
d) When the excessive amount cadmium ion are ingested, it replaces zinc ion at the key enzymatic sites, causing metabolic disorder.
e) High level of cadmium ion causes renal dysfunction, hypertension and cancer.
Biochemical Effects of Lead
Lead is a relative abundant of metal in nature occurring in lead minerals.
a) The major biochemical effect of lead is that its interference with heme-synthesis, which lead to hematological damage. Pb inhibit the several of key enzyme involved in the overall process of heme-synthesis whereby the metabolic intermediate accumulate.
b) The overall effect is the disruption of the synthesis of hemoglobin.
c) Pb does not permit the utilization of O2 and glucose for life sustanency energy production.
d) Higher level of Pb causes anaemia.
e) Elevated Pb levels in blood causes kidney dysfunction.
f) Elevated Pb levels in blood causes brain damage.
Tuesday, August 16, 2011
Classification of Toxic Chemicals
Classification of Toxic Chemicals
Toxic chemicals may be classified according to their function and effects. According to the “international resister of potentially toxic chemical” of the United Nations environment programme, there are four million known chemicals in the world today and another 30000 new compound are added to the list every year. Among these 60000 to 70000 chemicals are commodity used.
According to environment on which it present toxic chemicals are divided into two class:
1. Toxic chemicals in Air
2. Toxic chemicals in water.
1. Toxic chemicals in Air
About 24 extremely hazardous substances in the atmosphere. These are given below:
a) Acrylonitrile
b) As
c) Asbestos
d) Benzene
e) Be
f) Cd
g) Chlorinated solvent
h) CFC
i) Chromates
j) Coke oven emission
k) Diethyl stillbesterol
l) Dibromomonochloropropane
m) Ethylene dibromate
n) Ethylene oxide
o) Pb
p) Hg
q) Nitrosoamine
r) Ozone
s) Polybromominated biphenyl
t) Polychlorinated biphenyl
u) Radiation
v) Sulpher Dioxide
w) Vinyl chloride
x) Toxic waste.
2. Toxic chemicals in water.
A. Arsenic
Sources: mining by-product, pesticides, chem. Waste, etc.
Effects: Toxic, possibly carcinogenic, etc.
B. Cadmium
Sources: Industrial discharge, mining waste, metal plating, water pipes, etc.
Effects: Replaces Zn biochemical, causes high blood pressure, kidney damage, destruction of testicular tissue and red blood cell, toxicology to aquatic bio, etc.
C. Boron
Sources: Coal, Detergent formation, industrial waste, etc.
Effects: toxic to plants, etc.
D. Chromium
Sources: Metal plating, cooling tower, water additives, normally found as chromium polluted water, etc.
Effects: essential trace element, possibly carcinogenic, etc.
E. Copper
Sources: metal plating, industrial and domestic waste, mining, mineral leaching, etc.
Effects: Essential trace element not very toxic to animals, toxic to plant and algae at moderate levels, etc.
F. Fluorine
Sources: Natural geological sources, industrial waste and water additives, etc.
Effects: Prevent tooth decay about 1 mg/l.
G. Lead
Sources: Industry, mining, plumbing, coal, gasoline, etc.
Effects: Toxic, wild-life destroyed, etc.
H. Manganese
Sources: mining, industrial wastes, acid mine drainage, microbial action on manganese minerals at low potential, etc.
Effects: relatively non-toxic to animal, toxic to plant at higher level, stains material, etc.
I. Mercury
Sources: Industrial waste, mining, pesticide, coal, etc.
Effects: highly toxic, etc.
J. Molybdenum
Sources: industrial waste, industrial sources, etc.
Effects: possibly toxic to animal, essential to plant, etc.
K. Selenium
Sources: Natural geological sources, sulphur, coal, etc.
Effects: essential at low level and toxic at high level, etc.
L. Zinc
Sources: Industrial waste, metal plating, plumbing, etc.
Effects: Essential in many metallo-enzyme toxic to plant at higher level, etc.
M. Beryllium
Sources: Coal, nuclear power and space industry, etc.
Effects: Acute and chrome toxicity, possibly carcinogenic, etc.
Toxic Chemicals and its Effect on Enzeme
Toxic Chemicals
There are number of chemicals in the environment. Some of these are toxic and rest are non-toxic. The toxic chemicals are discharged by industries into air, water and soil. They get into human food chain from the environment. Once they enter our biological system, they disturb our biological processes leading in some caases to fatal diseases. Chemical toxicology is a branch of the modern technology for study of toxic chemicals and mode of action.
Schwardz used the term “concentration window” to draw the arbitrary lines of demarcation.
a) Essential at trace level for substance of trace level.
b) Deficient at lower than (a) causing metabolic disorder.
c) Toxic at higher than (a) causing adverse effect.
The effects of Toxic Chemicals on Enzyme
In general toxic chemicals attack the active sites of enzymes inhibiting essential enzyme function. Heavy metal atom e.g., Hg2+, Pb2+, Cd2+ act as a effective enzyme inhibitors. They have affinity for sulphur containing ligands e.g., SCH3 and –SH in methionic and cystonic amino acid which are the part of enzyme structure.
SH(Enzyme)SH + Hg2+ >>> S (Enzyme)SHg + 2H+
Metalloenzymes contain metals in their structures. Their action is inhibited when one metal ion of metallo-enzymes is replaced by another metal ion of similar size and charge.
As for example, Zn2+ in some metallo-enzymes is substituted by Cd+2 which leads to cadmium toxiacity. The enzyme inhibited by Cd2+ include alcohol dehydrogenase amylase, peptidase.
Monday, August 8, 2011
Fertilizer industry waste water treatment
Fertilizer industry waste water treatment
Sources:
Spill overs from manufactured of acids used as raw materials, spill over of the final fertilizer products, boiler blow down, cooling waters etc.
Properties
i. Effluent from ammonia production is highly alkaline.
ii. Effluent from phosphoric acid manufacturer is acidic.
iii. High amount of fluoride present in the phophatic fertilizer.
Bad Effects
i. Fertilizer effluents cause eutrophication due to algal bloom.
ii. Enrich the fluoride content of receiving waters causing dental skeletal fluorosis to human.
iii. Presence of Cr, CN-, NH3 are harmful to aquatic life.
iv. Abnormal calcification of bones in animals.
How to Treatment those
a) Segregation of wastes.
b) Removal of urea by hydrolysis.
c) Removal of fluoride and phosphate by precipating with chalk.
d) Removal of oil and greases by mechanical oil separation.
Sources:
Spill overs from manufactured of acids used as raw materials, spill over of the final fertilizer products, boiler blow down, cooling waters etc.
Properties
i. Effluent from ammonia production is highly alkaline.
ii. Effluent from phosphoric acid manufacturer is acidic.
iii. High amount of fluoride present in the phophatic fertilizer.
Bad Effects
i. Fertilizer effluents cause eutrophication due to algal bloom.
ii. Enrich the fluoride content of receiving waters causing dental skeletal fluorosis to human.
iii. Presence of Cr, CN-, NH3 are harmful to aquatic life.
iv. Abnormal calcification of bones in animals.
How to Treatment those
a) Segregation of wastes.
b) Removal of urea by hydrolysis.
c) Removal of fluoride and phosphate by precipating with chalk.
d) Removal of oil and greases by mechanical oil separation.
Waste water treatment of Leather Tanning Industries
Waste water treatment of Leather Tanning Industries
Sources:
Beam house washing, processing, soaking, tanning, liming, dehairing, deflushing, deliming, bating, picking, dyeing are the main source of waste water.
Characteristics
i. It contain excess NaCl.
ii. It has bad-odour.
iii. It has dark color.
iv. It has a high BOD value.
v. It has a high COD value.
vi. It contain suspended solids.
Bad Effects
i. The constituents of tannery effluent are deleterious and irrerespective.
ii. It imparts persistent dull brown to the receiving water.
iii. Highly repulsive odour is imparted to the receiving water.
iv. The acidic or alkaline effluent are corrosive to concrete and metal pipe.
v. Excess NaCl is corrosive.
vi. The effluent may be contain pathogenic bacteria..
vii. Dissolved Cr is harmful for fish.
viii. It has nonclear water.
How to Treatment those
i. Primary treatment includes screening to remove hairs, fleshing, fats etc.
ii. Secondary treatment includes processes such as chemicals coagulation and biological treatment.
iii. Removal of chromium followed by activated sludge process.
Sources:
Beam house washing, processing, soaking, tanning, liming, dehairing, deflushing, deliming, bating, picking, dyeing are the main source of waste water.
Characteristics
i. It contain excess NaCl.
ii. It has bad-odour.
iii. It has dark color.
iv. It has a high BOD value.
v. It has a high COD value.
vi. It contain suspended solids.
Bad Effects
i. The constituents of tannery effluent are deleterious and irrerespective.
ii. It imparts persistent dull brown to the receiving water.
iii. Highly repulsive odour is imparted to the receiving water.
iv. The acidic or alkaline effluent are corrosive to concrete and metal pipe.
v. Excess NaCl is corrosive.
vi. The effluent may be contain pathogenic bacteria..
vii. Dissolved Cr is harmful for fish.
viii. It has nonclear water.
How to Treatment those
i. Primary treatment includes screening to remove hairs, fleshing, fats etc.
ii. Secondary treatment includes processes such as chemicals coagulation and biological treatment.
iii. Removal of chromium followed by activated sludge process.
Waste water treatment from Electroplating Industries
Waste water treatment from Electroplating Industries
Sources: surface cleaning, pickling, stripping, electroplating, contribute alkali waste containg NaOH, carbonates, silicates wetting, greases and organic emulsifiers. Electroplating bath contains Cu, Ni, Ag, Zn, Cd, Cr, Sn, Pb, Fe etc.
Characteristics
i. The waste water contain some solvent such as trilene, benzene, petrol, aldehyde etc.
ii. It contain unused acids.
iii. It contains oil, greases as contaminant.
iv. It contain biodegradable solids.
v. It contain suspended solids.
vi. It has bad odour.
Bad Effects
i. Plating effeluent are highly toxic and corrosive.
ii. The toxicity of chemicals to microorgsnisms inhibits self purification properly of the stream.
iii. Fe, Sn etc. impart colour to the receiving stream.
iv. Phosphates and nitrates present in the effluent help in excessive algal growth.
v. Colloidal and suspended impurities impart unaesthetic appearance to the stream.
How to Treatment those
i. Segregation of cyanide wastes, chromium, wastes and other toxic metals bearing wastes.
ii. Treatment of cyanide waste by alkaline chlorination.
iii. Treatment of chromium bearing effluent.
iv. After the treatment of cyanide and chromium waste setting down the precipitation. Then the sludge may be dried on sand and disposed in landfills.
v. Scraping of the floating oils and greases from holding task.
vi. The rinse water may be reused after removing the ionic impurities.
Sources: surface cleaning, pickling, stripping, electroplating, contribute alkali waste containg NaOH, carbonates, silicates wetting, greases and organic emulsifiers. Electroplating bath contains Cu, Ni, Ag, Zn, Cd, Cr, Sn, Pb, Fe etc.
Characteristics
i. The waste water contain some solvent such as trilene, benzene, petrol, aldehyde etc.
ii. It contain unused acids.
iii. It contains oil, greases as contaminant.
iv. It contain biodegradable solids.
v. It contain suspended solids.
vi. It has bad odour.
Bad Effects
i. Plating effeluent are highly toxic and corrosive.
ii. The toxicity of chemicals to microorgsnisms inhibits self purification properly of the stream.
iii. Fe, Sn etc. impart colour to the receiving stream.
iv. Phosphates and nitrates present in the effluent help in excessive algal growth.
v. Colloidal and suspended impurities impart unaesthetic appearance to the stream.
How to Treatment those
i. Segregation of cyanide wastes, chromium, wastes and other toxic metals bearing wastes.
ii. Treatment of cyanide waste by alkaline chlorination.
iii. Treatment of chromium bearing effluent.
iv. After the treatment of cyanide and chromium waste setting down the precipitation. Then the sludge may be dried on sand and disposed in landfills.
v. Scraping of the floating oils and greases from holding task.
vi. The rinse water may be reused after removing the ionic impurities.
Saturday, August 6, 2011
Waste water treatment from Pulp and Paper Industries
Waste water treatment from Pulp and Paper Industries
Sources
The raw material preparation, pulping, washing, bleaching, chemical recovery, screening of pulp and paper making contribute to wash effluents.
Characteristics
i. The water is dark brown.
ii. It contain high percent of suspended solid.
iii. It contain high percent of dissolved solid.
iv. It has bad odour.
v. It has high COD.
vi. Resistant to biological oxidation.
Effects
i. The dark vlour imparts persistent colour to the receiving water stream and inhibits photosynthesis.
ii. The immediate oxygen demand of the effluent brings about depletion of oxygen of the receiving stream.
iii. The chemical present in the effluent are harmful to fauna and flora of the receiving water.
Treatment option
i. Recovery of bi-products.
ii. Preliminary and primary operation carried out to remove suspended matter.
iii. Chemical treatment to remove dissolved organics.
iv. Lagoonong for storage and biodegradation of organic matter.
Sources
The raw material preparation, pulping, washing, bleaching, chemical recovery, screening of pulp and paper making contribute to wash effluents.
Characteristics
i. The water is dark brown.
ii. It contain high percent of suspended solid.
iii. It contain high percent of dissolved solid.
iv. It has bad odour.
v. It has high COD.
vi. Resistant to biological oxidation.
Effects
i. The dark vlour imparts persistent colour to the receiving water stream and inhibits photosynthesis.
ii. The immediate oxygen demand of the effluent brings about depletion of oxygen of the receiving stream.
iii. The chemical present in the effluent are harmful to fauna and flora of the receiving water.
Treatment option
i. Recovery of bi-products.
ii. Preliminary and primary operation carried out to remove suspended matter.
iii. Chemical treatment to remove dissolved organics.
iv. Lagoonong for storage and biodegradation of organic matter.
Waste water treatment from Textile Industries
Textile Industry
Sources:
i. Cotton textile industry: Various operations involved in a cotton textile mill are combing, spinning, sizing, weaving and knitting are the main source of waste water.
ii. Synthetic textile industry: The operations like scouring, dyeing, rinsing, bleaching and finishing are the source of waste water.
iii. Wool industry: Various operations involved in a cotton textile mill are combing, spinning, sizing, weaving and knitting are the main source of waste water in wool industryalso.
Characteristics
i. The waste water generally coloured.
ii. It contain starch, polyvinyl alcohol and softners.
iii. It has a high BOD and high dissolved minerals.
iv. It contains suspended solids.
v. It contains soap-alkaly etec.
Effects
i. The dyes present impart persistent colour to the receiving sterams and interfere with photosynthesis of phytoplankton.
ii. The high pH is deleterious to aquatic life.
iii. The colloidal and suspended impurities causes turbidity in the receiving waters.
iv. The oil present interferes with the oxygenation of the receiving water stream.
v. The dissolved minerals increase salinity of the water.
vi. The toxic chemicals destroys fish and other microbial organism.
vii. It depletes the dissolved oxygen.
viii. The dissolved solid form incrustations on the surface of the surface of the sewers.
ix. The dissolved impurities cause corrosion in the metallic parts.
Treatment options
i. Segregation of wasters.
ii. Screening to remove coarse suspended matter.
iii. Removal of grease by equalization, neutralization.
iv. Chemical coagulation to remove colour, suspended and colloidal impurities.
v. Aerobic biological treatment.
vi. Finally tertiary treatment to remove dissolved solid.
Sources:
i. Cotton textile industry: Various operations involved in a cotton textile mill are combing, spinning, sizing, weaving and knitting are the main source of waste water.
ii. Synthetic textile industry: The operations like scouring, dyeing, rinsing, bleaching and finishing are the source of waste water.
iii. Wool industry: Various operations involved in a cotton textile mill are combing, spinning, sizing, weaving and knitting are the main source of waste water in wool industryalso.
Characteristics
i. The waste water generally coloured.
ii. It contain starch, polyvinyl alcohol and softners.
iii. It has a high BOD and high dissolved minerals.
iv. It contains suspended solids.
v. It contains soap-alkaly etec.
Effects
i. The dyes present impart persistent colour to the receiving sterams and interfere with photosynthesis of phytoplankton.
ii. The high pH is deleterious to aquatic life.
iii. The colloidal and suspended impurities causes turbidity in the receiving waters.
iv. The oil present interferes with the oxygenation of the receiving water stream.
v. The dissolved minerals increase salinity of the water.
vi. The toxic chemicals destroys fish and other microbial organism.
vii. It depletes the dissolved oxygen.
viii. The dissolved solid form incrustations on the surface of the surface of the sewers.
ix. The dissolved impurities cause corrosion in the metallic parts.
Treatment options
i. Segregation of wasters.
ii. Screening to remove coarse suspended matter.
iii. Removal of grease by equalization, neutralization.
iv. Chemical coagulation to remove colour, suspended and colloidal impurities.
v. Aerobic biological treatment.
vi. Finally tertiary treatment to remove dissolved solid.
Water Treatment
Water Treatment
The various methods used in sewage and industrial waste water treatment are as follows-
1. Preliminary treatment : The principle objectives of preliminary treatment are the removal of gross solid, i.e., large floating and suspended solid matters, girt, oil and grease if they present in considerable quantities.
2. Primary treatment: After removal of gross solids, gritty materials and excessive quantities of oil and grease, the next step is to remove the remaining suspended solids as much as possible. The step is aimed at reducing the strength of the waste water and also to facilate secondary treatment.
The methods used for primary treatment are-
a) Sedimentation
b) Sedimentation aids
c) Mechanical flocculation
d) Chemical coagulation
e) Coagulants acids
f) Equalization
g) Neutralization
3. Secondary treatment: In this treatment, the dissolved and colloidal organic matter present in waste waters is removed by biological process involving bacteria and other microorganisms. This treatment is of two types-
a) Aerobic process: In this process, bacteria and other microorganisms consume organic matters as food.
i. Activated sludge process
ii. Lagooning process
b) Anaerobic process: This is mainly used for the digestion of sludges.
4. Biochemical treatment :
i. Aerated lagoons
ii. Trickling filters
iii. Activated sludge process
iv. Oxidation ditch process
v. Oxidation pond
vi. Anaerobic digestion
5. Tertiary treatment: Tertiary treatment is the final treatment meant for polishing the effluents from the secondary treatment processes to improve its quality further. The major objectives of tertiary treatment are –
a) Removal of fine suspended solids
b) Removal of bacteria
c) Removal of dissolved inorganic solid
d) Removal of final traces of organic.
The various methods used in sewage and industrial waste water treatment are as follows-
1. Preliminary treatment : The principle objectives of preliminary treatment are the removal of gross solid, i.e., large floating and suspended solid matters, girt, oil and grease if they present in considerable quantities.
2. Primary treatment: After removal of gross solids, gritty materials and excessive quantities of oil and grease, the next step is to remove the remaining suspended solids as much as possible. The step is aimed at reducing the strength of the waste water and also to facilate secondary treatment.
The methods used for primary treatment are-
a) Sedimentation
b) Sedimentation aids
c) Mechanical flocculation
d) Chemical coagulation
e) Coagulants acids
f) Equalization
g) Neutralization
3. Secondary treatment: In this treatment, the dissolved and colloidal organic matter present in waste waters is removed by biological process involving bacteria and other microorganisms. This treatment is of two types-
a) Aerobic process: In this process, bacteria and other microorganisms consume organic matters as food.
i. Activated sludge process
ii. Lagooning process
b) Anaerobic process: This is mainly used for the digestion of sludges.
4. Biochemical treatment :
i. Aerated lagoons
ii. Trickling filters
iii. Activated sludge process
iv. Oxidation ditch process
v. Oxidation pond
vi. Anaerobic digestion
5. Tertiary treatment: Tertiary treatment is the final treatment meant for polishing the effluents from the secondary treatment processes to improve its quality further. The major objectives of tertiary treatment are –
a) Removal of fine suspended solids
b) Removal of bacteria
c) Removal of dissolved inorganic solid
d) Removal of final traces of organic.
Wednesday, August 3, 2011
Water Pollutants
Water Pollutants
Water pollutants mainly classified into five class. These are-
1. Organic pollutants
2. inorganic pollutants
3. Suspended solids and sediment
4. Radio active material
5. Heat
1. Organic pollutants
Organic pollutants may be further categorized as follows
A. Oxygen demanding wastes: these include domestic and animal sewage biodegradable organic compounds and industrial waste, food processing plants, slaughter-houses, paper and pulp mills, tanneries etc. as well as agricultural run-off. All these wastes under degradation and decomposition by bacterial activity in presence of dissolved oxygen.
B. Disease causing waste: These include pathogenic microorganism in which may enter the water along with sewage and other wastes and may cause tremendous damage to public health. These microbes comprising mainly of virus and bacteria can cause dangerous water-born diseases such as cholera, typhoid, dysentery, polio and infections hepatitis in humans.
C. Synthetic organic compound: These are the man-made materials such as synthetic pesticides, synthetic detergent, food-additives, pharmaceuticals, insecticides, paints, synthetic fibers, elastomers, solvents, plasticizers, plastic and other industrial chemicals. Most of these chemicals are potentially toxic to plants, animal and human.
D. Sewage and agricultural run-off: Sewage and run-off from agricultural landssupply plant nutrients, which may stimulate the growth of algae and aquatic weeds in the receiving water body. This unwidely plant-growth results in the degradation of the value of the water body intented for reactional and other uses. Further, the water body loses all its Dissolved Oxygen in the long run up as a dead pool of water.
E. Oil : Oil pollution may take place because of oil spills from cargo oil tankers on the seas, losses during off-shore exploration and production of oil, accidental fires in ships and oil tankers, accidental or intentional oil slicks and leakage from oil pipe line, crossing water ways and reservoirs.
2.Inorganic pollutants
These comprise of mineral acids, inorganic salts, finely devided metals or metal componds, trace elements, cyanides, sulphates, nitrates, organometallic compounds and complexes of metals with organic compound present in the natural water. The trace element include Hg, As, Cd, Pb, Sb, Se etc.
3. Suspended solids and sediment: It denotes the particles floating, immersed and sedimented in the water and water body.
4. Radio-active element: The radio-active water pollutants may originate from anthropogenic activities:
A. Mining or processing of ores e.g., Uranium tailing.
B. Increasing the use of radioactive isotopes in the research, agricultural, industrial and mechanical application.
C. Radioactive material from nuclear power plant and reactor.
D. Radioactive material from testing and use of nuclear weaponry.
5. Heat: Waste heat is produced in all process iin which heat is converted into mechanical work. Thus consideration thermal pollution results from thermal power plants, particularly nuclear power based electrically plants.
Water pollutants mainly classified into five class. These are-
1. Organic pollutants
2. inorganic pollutants
3. Suspended solids and sediment
4. Radio active material
5. Heat
1. Organic pollutants
Organic pollutants may be further categorized as follows
A. Oxygen demanding wastes: these include domestic and animal sewage biodegradable organic compounds and industrial waste, food processing plants, slaughter-houses, paper and pulp mills, tanneries etc. as well as agricultural run-off. All these wastes under degradation and decomposition by bacterial activity in presence of dissolved oxygen.
B. Disease causing waste: These include pathogenic microorganism in which may enter the water along with sewage and other wastes and may cause tremendous damage to public health. These microbes comprising mainly of virus and bacteria can cause dangerous water-born diseases such as cholera, typhoid, dysentery, polio and infections hepatitis in humans.
C. Synthetic organic compound: These are the man-made materials such as synthetic pesticides, synthetic detergent, food-additives, pharmaceuticals, insecticides, paints, synthetic fibers, elastomers, solvents, plasticizers, plastic and other industrial chemicals. Most of these chemicals are potentially toxic to plants, animal and human.
D. Sewage and agricultural run-off: Sewage and run-off from agricultural landssupply plant nutrients, which may stimulate the growth of algae and aquatic weeds in the receiving water body. This unwidely plant-growth results in the degradation of the value of the water body intented for reactional and other uses. Further, the water body loses all its Dissolved Oxygen in the long run up as a dead pool of water.
E. Oil : Oil pollution may take place because of oil spills from cargo oil tankers on the seas, losses during off-shore exploration and production of oil, accidental fires in ships and oil tankers, accidental or intentional oil slicks and leakage from oil pipe line, crossing water ways and reservoirs.
2.Inorganic pollutants
These comprise of mineral acids, inorganic salts, finely devided metals or metal componds, trace elements, cyanides, sulphates, nitrates, organometallic compounds and complexes of metals with organic compound present in the natural water. The trace element include Hg, As, Cd, Pb, Sb, Se etc.
3. Suspended solids and sediment: It denotes the particles floating, immersed and sedimented in the water and water body.
4. Radio-active element: The radio-active water pollutants may originate from anthropogenic activities:
A. Mining or processing of ores e.g., Uranium tailing.
B. Increasing the use of radioactive isotopes in the research, agricultural, industrial and mechanical application.
C. Radioactive material from nuclear power plant and reactor.
D. Radioactive material from testing and use of nuclear weaponry.
5. Heat: Waste heat is produced in all process iin which heat is converted into mechanical work. Thus consideration thermal pollution results from thermal power plants, particularly nuclear power based electrically plants.
COD
COD
COD means chemical oxygen demand. COD is a measure of the oxygen equivalent to that portion of organic matter present in the waste matter sample that is suscsptible to oxidation by potassium dichromate.
Amount of oxygen required by organic matter in a sample of water for its oxidation by strong chemical. Oxidizing agent such as potassium dichromate. According to the ASTM, COD is defined as the amount of oxygen consumed under specified conditions in the oxidation of organic matter and oxidisable inorganic matter, corrected for the influence of chlorine.
COD is important and quickly measured parameter for stream, sewage and industrial waste samples to determine their pollutional strength.
Determination of COD
The principle involved in the determination of COD is that when the waste water sample is refluxed with a known excess of potassium dichromate in a 50% sulphuric acid solution in presence of AgSO4 and HgSO4, the organic matter of the sample is oxidized to water, CO2 and NH3. The excess dichromate remaining unreacted in the solution is titrated with a standard solution of ferrous ammonium sulphate. The COD of the sample is calculated as follows
(V2- V1) × N × 8 × 1000
COD = -----------------------------------------
X
Where, V1 and V2 are volumes of ferrous ammonium sulphate, N is normality run down in the blank and test experients respectively and X is the volume of the sample taken for the test.
COD means chemical oxygen demand. COD is a measure of the oxygen equivalent to that portion of organic matter present in the waste matter sample that is suscsptible to oxidation by potassium dichromate.
Amount of oxygen required by organic matter in a sample of water for its oxidation by strong chemical. Oxidizing agent such as potassium dichromate. According to the ASTM, COD is defined as the amount of oxygen consumed under specified conditions in the oxidation of organic matter and oxidisable inorganic matter, corrected for the influence of chlorine.
COD is important and quickly measured parameter for stream, sewage and industrial waste samples to determine their pollutional strength.
Determination of COD
The principle involved in the determination of COD is that when the waste water sample is refluxed with a known excess of potassium dichromate in a 50% sulphuric acid solution in presence of AgSO4 and HgSO4, the organic matter of the sample is oxidized to water, CO2 and NH3. The excess dichromate remaining unreacted in the solution is titrated with a standard solution of ferrous ammonium sulphate. The COD of the sample is calculated as follows
(V2- V1) × N × 8 × 1000
COD = -----------------------------------------
X
Where, V1 and V2 are volumes of ferrous ammonium sulphate, N is normality run down in the blank and test experients respectively and X is the volume of the sample taken for the test.
BOD
BOD
BOD means Biochemical Oxygen Demand. BOD represents the quantity of oxygen required by bacteria and other microorganisms during the biochemical degradation and transformation of organic matter present in waste water under aerobic conditions.
BOD test is important-
1. In analysis of sewage.
2. In analysis of industrial effluents.
3. In analysis of polluted water.
4. For assessing organic pollution.
5. For containing stream pollution.
Determination of BOD
The BOD test is essentially consists of measurements of dissolved oxygen content of the sample, before and after incubation at 20 °C for 5 days. If the sample does not contain any oxygen, it supplied with oxygen and the depletion caused is calculated as the measure of BOD.
Number of gram of oxygen required
Thus BOD = --------------------------------------------------------------
Number of liters of sample
While carrying out the BOD test, microbial organism may be also be provided if necessary. The BOD is usually expressed as mg/l.
BOD means Biochemical Oxygen Demand. BOD represents the quantity of oxygen required by bacteria and other microorganisms during the biochemical degradation and transformation of organic matter present in waste water under aerobic conditions.
BOD test is important-
1. In analysis of sewage.
2. In analysis of industrial effluents.
3. In analysis of polluted water.
4. For assessing organic pollution.
5. For containing stream pollution.
Determination of BOD
The BOD test is essentially consists of measurements of dissolved oxygen content of the sample, before and after incubation at 20 °C for 5 days. If the sample does not contain any oxygen, it supplied with oxygen and the depletion caused is calculated as the measure of BOD.
Number of gram of oxygen required
Thus BOD = --------------------------------------------------------------
Number of liters of sample
While carrying out the BOD test, microbial organism may be also be provided if necessary. The BOD is usually expressed as mg/l.
Water Pollution and DO
Water Pollution
Any human activity that impairs the use of water as a resource may be called water pollution.
Therefore, addition of excess of undesirable substances to water that makes it harmful to man, animal and aquatic life or other wise causes significant departures from the normal activity of various living communities in and around water is called water pollution.
Dissolved Oxygen
DO means Dissolved Oxygen. The optimum DO in natural waters is 4-6 ppm, which is essential for supporting aquatic life. Any decrease in this DO value is an index of pollution. Many aquatic organisms can not survive at lower DO levels in water.
Determination of Dissolved Oxygen
The DO content of a water sample is determined iodometrically by the Modified Winker’s method. The principle involved in this method is that when manganous sulphate is added to the water sample containing alkaline potassium iodide, manganese hydroxide is formed.
This is oxidized to basic manganic oxide by the DO present in the water sample. When the sulphuric acid is added, the basic manganic oxide liberates iodine, which is equivalent the DO originally present in the water sample. The liberated iodine is titrated with standard hypo solution, using starch as a indicator.
Interference due to nitrate can be determined by adding sodium azide to the alkaline potassium iodide solution used above.
MnSO4 + 2KOH >> Mn(OH)2 + K2SO4
2Mn(OH)2 + O2 (from DO) >> 2MnO(OH)2
2MnO(OH)2 + 2 H2SO4 >> Mn(SO4)2 + H2O
Mn(SO4)2 + KI >> MnSO4 + K2SO4 + I2
2 Na2S2O3 + I2 >> Na2S4O6 + 2NaI
The DO is usually expressed as mg/l (ppm).
Any human activity that impairs the use of water as a resource may be called water pollution.
Therefore, addition of excess of undesirable substances to water that makes it harmful to man, animal and aquatic life or other wise causes significant departures from the normal activity of various living communities in and around water is called water pollution.
Dissolved Oxygen
DO means Dissolved Oxygen. The optimum DO in natural waters is 4-6 ppm, which is essential for supporting aquatic life. Any decrease in this DO value is an index of pollution. Many aquatic organisms can not survive at lower DO levels in water.
Determination of Dissolved Oxygen
The DO content of a water sample is determined iodometrically by the Modified Winker’s method. The principle involved in this method is that when manganous sulphate is added to the water sample containing alkaline potassium iodide, manganese hydroxide is formed.
This is oxidized to basic manganic oxide by the DO present in the water sample. When the sulphuric acid is added, the basic manganic oxide liberates iodine, which is equivalent the DO originally present in the water sample. The liberated iodine is titrated with standard hypo solution, using starch as a indicator.
Interference due to nitrate can be determined by adding sodium azide to the alkaline potassium iodide solution used above.
MnSO4 + 2KOH >> Mn(OH)2 + K2SO4
2Mn(OH)2 + O2 (from DO) >> 2MnO(OH)2
2MnO(OH)2 + 2 H2SO4 >> Mn(SO4)2 + H2O
Mn(SO4)2 + KI >> MnSO4 + K2SO4 + I2
2 Na2S2O3 + I2 >> Na2S4O6 + 2NaI
The DO is usually expressed as mg/l (ppm).
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