Test: Environmental Awareness (Water Pollution) - Software Development MCQ

Key Points

• Water is called the "universal solvent" because it is capable of dissolving more substances than any other liquid.
• This is important to every living thing on earth.
• This allows the water molecule to become attracted to many other different types of molecules.
• Water has no definite shape.
• It is tasteless.
• It is odourless.
• It is colourless.
• Any colour present in water is due to the presence of dissolved or suspended impurities in it.
• Materials like air, water, and clear glass are called transparent.
• When light encounters transparent materials, almost all of it passes directly through them. 
• Pure water (solely hydrogen and oxygen atoms) has a neutral pH of 7, which is neither acidic nor basic.
• Water should be free from nitrogen organic matter.
• Density: 997 kg/m³
• Boiling point: 212°F (100°C)
• Molar mass: 18.01528 g/mol
• Melting point: 32°F (0°C)
• Formula: H2O
• IUPAC ID: Water, Oxidant

Thus, pure water is tasteless, odourless, colorless.

• Pollution is any undesirable change in physical, chemical, or biological characteristics of air, land, water, or soil.
• Agents that bring about such an undesirable change are called pollutants.
• Pollution can be broadly classified into 4 types - Air pollution, Water pollution, Noise pollution & Soil pollution.

Important Points

• Water pollution occurs when there is an addition of undesirable substances into water bodies.
• The sources of water pollution can be divided into 2 major groups:
  • Point source - It refers to the single identifiable sources like discharge pipes from a factory or sewage plant.
  • Non-point source - It refers to sources that do not originate from a single point. Example - agricultural run-offs.
• Factories and sewage treatment plants have proper drainage pipes leading to a water body for disposing their wastes and thus they are point sources of water pollution.
• Urban and Suburban lands cause water pollution by the field run offs and thus do not originate from a single point. Hence, they are non-point sources of water pollution.

Use of Alum:

• Alum, also known as aluminium sulfate (Al₂(SO₄)₃.18H₂O) is added to water in order to help in the sedimentation of suspended impurities.
• Alum is a universal coagulant.
• It destabilizes the mud particles suspended in it through the process known as coagulation. 
• Alum when added to water attaches to the suspended particles and increases their size forming a floc.
• This floc is due to an increase in size and weight settling at the bottom of the container.
• These are removed by pouring out the clean water layer formed at the top.

Thus, Rekha's mother adds Phitkari (Alum) to water collected from the pond every day in order to sediment light-suspended impurities.

Additional Information 

• Hard water is water that contains a high amount of dissolved minerals (calcium and magnesium salts in the form of bicarbonates, chlorides, and sulfates.)
• Hard water does not lather with soap.
• Soft water is surface water that contains low dissolved minerals.
• Alum does not kill germs, in general, bleaching powder is used to kill germs in the water.
• Alum does not decolourize water.

Minamata disease:

• Minamata disease is sometimes referred to as Chisso-Minamata disease.
• The disease Minamata was first discovered in 1956 in Japan.
• It is a neurological syndrome caused by severe mercury poisoning.
• It is methylmercury (MeHg) poisoning that occurred in humans who ingested fish and shellfish contaminated by MeHg discharged in wastewater.
• Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision, and damage to hearing and speech. 

Itai-Itai:

• Itai-Itai, which literally translates to ‘it hurts, it hurts’ is the name given to cadmium poisoning.
• This name was given to the disease by the locals of Toyama Prefecture of Japan in 1912.
• This disease was recognized as the Four Big Pollution Diseases of Japan.
• Cadmium is a naturally occurring toxic heavy metal.
• It is an extremely toxic industrial and environmental pollutant classified as a human carcinogen.
• It is used in the manufacturing of NiCd rechargeable batteries.

Thus, Minamata and Itai-Itai diseases caused by metallic water pollution are caused by Hg and Cd metals respectively.

Additional Information

Brief details about the diseases caused by environmental degradation: 

• All living organisms need oxygen to live.
• Plants and animals directly take up oxygen from the air.
• Fish, like all other complex life forms, need oxygen to survive.
• They get theirs in the form of oxygen gas dissolved in the water.
• When sewage is dumped in the water body the wastewater in the pond starts to decompose at a rapid rate.
• This decomposition process leads to the depletion of oxygen in the water body.
• When the dissolved oxygen present in the water decreases the fishes die.

Key Points

Biochemical Oxygen Demand (BOD)

• BOD (Biological Oxygen Demand) is the amount of oxygen necessary for bacteria to consume the organic material in water.
• Organic material that is discharged into natural waters causes a rapid increase in the growth of microorganisms that deplete the oxygen required for other aquatic life. 
• The BOD is an important parameter for assessing water quality and water pollution.
• It deals with the amount of oxygen consumption by aerobic biological organisms to oxidize organic compounds.
• Sewage with high BOD can cause a decrease in the oxygen of receiving waters, which in turn can cause the death of some organisms.
• When wastewater is discharged into the water body the Dissolved Oxygen (DO) of the water body decreases.
• More the polluted water, more the BOD and lower the DO.

Hence, the BOD of the water will increase if the organic matter is mixed with water.

Concept: 

• Water is a cyclic resource with abundant supplies on the globe.
• Approximately, 71 per cent of the earth’s surface is covered with it but freshwater constitutes only about 3 per cent of the total water.
• In fact, a very small proportion of fresh water is effectively available for human use.
• The availability of fresh water varies over space and time.
• Water is one of the most important resources on earth as it is required for all day to day activities.
• It is required for drinking, washing, cooking as well as forms an essential part of the body of all living organisms.
• Geographically, water is required to ensure a balance of seasons.

Explanation:

• Water scarcity will possibly pose the greatest challenge on earth.
• It is because of increased demand coupled with shrinking supplies.
• There is over utilisation of water due to increasing population which is also one of the causes of increasing water pollution.
• Water pollution is the addition of unwanted material into water that makes it unfit for human consumption.
• With increasing reliance on water bodies for waste disposal etc, there has been ever-increasing water pollution.

∴ We should conserve water because:

• less water is available for usage
• the demand for water has increased
• water pollution has increased

• Water disinfection means purifying the water by killing or deactivating microorganisms or pathogens. 
• Various methods are used to disinfect the water.

Key Points

Chlorine

• Chlorine (Cl), chemical element, the second lightest member of the halogen family elements, or Group 17 (Group VIIa) of the periodic table.
• Chlorine is a toxic, corrosive, greenish-yellow gas that is jittery to the eyes and to the respiratory system.
• Chlorination ​is the process of adding chlorine to the water to kill pathogens or disinfect the water.
• It is an effective method of water purification.
• Chlorine kills a large variety of microorganisms.
• They are the most prefred and common method of water purification on regular basis.

Ozone: 

• At present Ozone is also being used as a disinfectant for the purification of water.
• Ozone is a powerful oxidizing agent which gets dissolved in water easily and produces a broad spectrum biocide that kills all bacterias, viruses.
• Ozone is a strong oxidizing agent which is 51% stronger than chlorine and its effective rate is 3.125 times faster than other disinfectants.
• However, they are not the preferred method of water purification in cities as they are very expensive to use and requires a proper setup.

Iodine:

• Iodine is an effective, simple, and cost-efficient means of water disinfection.
• Iodine used for water purification is commonly added to water as a solution.
• The iodine kills many, but not all, of the most common pathogens present in natural freshwater sources.
• It is the preferred method of water purification in the case of emergencies.

Radiation:

• Ultraviolet (UV) rays are part of the light that comes from the sun.
• UV in water purification technique is known to be an effective disinfectant due to its strong germicidal (inactivating) ability.
• UV disinfects water containing bacteria, protozoa, and viruses.
• UV does not add any chemical taste or odour to the water.
• It is a very expensive method of water purification and is usually done for a smaller setup.

​Thus, iodine is used for emergency disinfection of water.

Concept:

• Water is very important for human survival.
• Water in raw form contains various impurities such as harmful chemicals and microorganisms that cause disease.

Explanation:

• There are various ways to purify water.

Boiling

• Boiling is the traditional method used to purify the water.
• Various microorganisms have the capability to survive only at a favourable temperature.
• So when we boil the water, It kills almost all the pathogens present in it.
• So, it is also an effective method for purifying the water.

Filtering

• Filtration is the process used to separate unwanted particles from liquid or gases.
• It uses a filter medium through which the solution has to pass.
• The filter medium allows only the liquid to pass but not solid.
• Filtration can be of any kind biological, physical or mechanical.
• Filtration can help in purifying the water.

​Sterilizing

• Sterilization of the water is also an effective method to purify the water.
• It kills or eliminates all the microorganism that present in the water.
• It helps in preventing the water borne disease.

Thus, boiling, filtering and sterilizing all are the method to purify the water.

Additional Information

Other methods used to purify the water are as follows:

Purification by chlorine tablets:

• Chlorination ​is the process of adding chlorine to the water to kill pathogens or disinfect the water.
• It is an effective method of water purification.
• Chlorine kills a large variety of microorganisms.

Coagulation:

• ​The process of adding alum to the water to disinfect the water is called coagulation.
• Alum acts as an electrolyte present in the water that attracts all the unwanted particles present in the water.
• This helps in settling down the suspended particles in the water.
• So, it is also an effective method for purifying the water.

Permissible limits for different compounds are as follows:

Activated sludge process:

• The essential features of the activated sludge process are an aeration stage, solids-liquid separation following aeration, and a sludge recycle system.
• Wastewater after primary treatment enters an aeration tank where the organic matter is brought into intimate contact with the sludge from the secondary clarifier.
• It requires less space, does not produce obnoxious odor, and requires less time for wastewater treatment.
• It requires skilled supervision

Important point:

Followings are the classification of secondary treatment units:

(i) The COD (Chemical oxygen demand) test is used to measure the content of organic matter of waste water, both biodegradable and non-biodegradble.

(ii) The COD test uses potassium dichromate (K₂Cr₂O₇) in presence of concentrated sulfuric acid (H₂SO₄) solution that oxidizes both organic (predominate) and inorganic substances in a waste water sample.

(iii) The reagents for COD test are followings:

• Standard potassium dichromate solution (0.25N)
• Concentrated sulfuric acid
• Standard ferrous ammonium sulphate titrant (0.1N)
• Ferroin indicator solution.

Water pollution occurs when harmful substances, chemicals or microorganisms contaminate a stream, river, lake, ocean, aquifer, or other body of water, degrading water quality and rendering it toxic to humans or the environment.​

Key-Points

Organic pollution may refer to the concentration of organic compounds in water including dissolved and suspended biogenic substances from aquatic and terrestrial species. 

• Run-off urban areas: 
  • Urban runoff is surface runoff of rainwater created by urbanization.
  • This runoff is a major source of flooding and water pollution in urban communities worldwide.
  • Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development which results in high amount of surface runoff.
  • It is mostly inorganic in nature with gasoline, motor oil, heavy metals, trash and other pollutants from roadways and parking lots.
• Run-off from agricultural forms: 
  • Agricultural Runoff is water from farm fields due to irrigation, rain, or melted snow that flows over the earth that can absorb into the ground, enter bodies of waters or evaporate.
  • This runoff can contain organic pollutants like pesticides, sediment (soil particles), nutrients (phosphorus, nitrogen and potassium from fertilizers) and metals, which can contaminate sources of water.
• Sewage effluents:
  • Sewage, or domestic/municipal wastewater, is a type of wastewater that is produced by a community of people.
  • It is characterized by physical, chemical and toxic constituents, and its bacteriologic status.
  • It consists mostly of greywater (from sinks, bathtubs, showers, dishwashers, and clothes washers), blackwater (the water used to flush toilets, combined with the human waste that it flushes away), soaps and detergents, and toilet paper (less so in regions where bidets are widely used instead of paper). 
  • Sewage effluents have the highest amount of organic pollutants along with bacterial contamination.
• Industrial effluents:
  • Industrial effluent is the wastewater produced by industrial activity.
  • It includes wastewater produced from manufacturing process or cleaning process.
  • The composition of wastewater generated mostly depends on the nature of industry.
  • It is mostly inorganic in nature.

The typical steps in a conventional wastewater treatment follows the sequence is

Screening – Sedimentation – Aerobic oxidation – Disinfection – Discharge

The four processes of wastewater treatment are:

1. Preliminary Treatment

• Screening (screeners, grit chambers, and skimming tanks)

2. Primary Treatment

• Sedimentation (basically involves the process of sedimentation or settling),
• Chemical-aided Sedimentation

3. Secondary or Biological Treatment

• Activated sludge process
• Aerated lagoons         
• Sequencing batch reactor
• Aerobic digestion
• Trickling filters
• Rotating biological contractors

4. Tertiary or Advanced Treatment

• Solids removal
• Biological nitrogen removal
• Biological phosphorus removal
• Disinfection.

• The hardness of water is that characteristic that prevents the formation of sufficient leather or foam.
• It occurs due to the presence of carbonates, bicarbonates, sulphates, chlorides of calcium and magnesium(Ca and Mg).
• The hardness of water is due to the presence of dissolved minerals of Ca2+, Mg2+, Al3+, Iron and other heavy elements. Specifically due to Calcium Sulphate, Calcium Bicarbonate, Calcium chloride, Magnesium Sulphate, Magnesium Bicarbonate and Magnesium chloride.​

Concept:

Physical Pollution of Water:

• It is essential to regularly assess the physical properties of water quality in order to determine if the water is polluted or not.
• Physical traits can be identified using:
• Taste and Odor:
  • The taste and odour of clean water are always undetectable.
  • Any taste or smell could be an indication of water pollution.
• Colour:
  • Polluted water may be coloured; pure water is colourless.
• Temperature:
  • In natural water systems like lakes and rivers, temperature is a critical physical factor that impacts water quality.
• Turbidity:
  • The opposite of clear, light-unabsorbent water is turbidity.
  • The presence of turbidity in the water could indicate water pollution.
• Particles:
  • If water is filtered to remove suspended solids, the solid that remains in the water can be used to calculate the number of dissolved solids.
  • Dissolved solids in water that exceed 300 mg/l have a negative impact on both industrial and living objects.

Explanation:

pH Value: 

• Taking measurements of elements like pH and dissolved oxygen is necessary to analyse the chemical properties of water:
• The pH scale, which spans from 0 to 14, is used to determine whether water is acidic or alkaline.
• A logarithmic scale is used for measurement.
• Dissolved oxygen is the amount of free, non-compound oxygen that is present in water or other liquids.
• It is a significant aspect in determining water quality because of its effect on the aquatic life present in a body of water.

Thus, pH value is not involved in the physical pollution of water. 

Concept:

The biochemical oxygen demand of safe drinking water is zero.

BOD represents the amount of biodegradable organic matter present in water. It also indicates the amount of treatment required for purifying. If the BOD is high the extent of treatment required will be high.

Hence, there should not be any BOD in safe drinking water.

Important Points

The permissible limits of various compounds are as follows:

The correct answer is Tertiary Treatment.

Concept:

• Sewage treatment is the process of cleaning polluted water before it is discharged into bodies of water.

Explanation:

• Sewage water treatment is carried out in three stages:

Primary treatment:

• This involves the physical removal of particles from the sewage through filtration and sedimentation.
• Floating debris is initially removed through sequential filtration.
• Then the grit is removed by sedimentation.
• The settled solids from the primary sludge and the supernatant from the effluent.

Secondary treatment:

• The primary effluent is passed in aeration tanks and constantly agitated mechanically.
• Air is pumped into it. 
• This promotes the growth of beneficial aerobic microbes that consume organic matter in the effluent.

Tertiary treatment:

• It is the advanced treatment process that follows secondary wastewater treatment and produces high-quality water.
• Tertiary treatment of wastewater includes the removal of nutrients such as phosphorus and nitrogen, as well as removing all suspended and organic matter. 
• Then, the water is sent to the natural source.

​

The correct answer is All of the above.

Concept:

• Water is called the "universal solvent" because it is capable of dissolving more substances than any other liquid.
• This is important to every living thing on earth.
• This allows the water molecule to become attracted to many other different types of molecules.
• Water has no definite shape.
• It is tasteless.
• It is odourless.
• It is colourless.
• Any colour present in water is due to the presence of dissolved or suspended impurities in it.
• Materials like air, water, and clear glass are called transparent.
• When light encounters transparent materials, almost all of it passes directly through them. 
• Pure water (solely hydrogen and oxygen atoms) has a neutral pH of 7, which is neither acidic nor basic.
• Water should be free from nitrogen organic matter.

Explanation:

• The United Nations (UN) and other governments have recognized clean drinking water to be a fundamental human right and a necessary step toward improving living conditions.
• Safe drinking water is the water that can is safe for drinking, food preparation, personal hygiene, and other domestic purposes.
• The water must meet the required chemical, biological and physical quality standards at the point of supply to the users.
• Pathogenic agents such as Escherichia coli, Vibrio cholera, Yersinia enterocolitica, Campylobacter jejuni, and Campylobacter coli, could be present in water which makes the water unhealthy for consumption.
• Harmful chemicals such as Chlorine, Chloramines, Mercury, VOCs, etc. can be present in water.

Additional Information

•  The UN Committee of Economic, Social, and Cultural Rights issued General Comment No. 15 on the right to water in November 2002, declaring that "the human right to water entitles everyone to adequate, safe, acceptable, physically accessible, and inexpensive water for personal and household needs."
• "Not only is universal access to sanitation vital for human dignity and privacy, but it is also one of the primary strategies for safeguarding the quality" of water supplies.

• Pollution occurs when a substance present in the environment prevents the functioning of natural processes and produces harmful environmental and health effects.
• In the natural world, many substances accumulating in the environment are processed through the intricate network of biogeochemical cycles.
• Water pollution occurs when harmful substances, chemicals or microorganisms contaminate a stream, river, lake, ocean, aquifer, or other body of water, degrading water quality and rendering it toxic to humans or the environment.​

Key Points

​Sources: 

• industrial effluents
• agricultural runoffs
• surface runoffs
• the municipality (urban) and domestic wastes
• substances produced from energy production
• mining
• oil spill

Important Points

Run-off urban areas: 

• Urban runoff is surface runoff of rainwater created by urbanization.
• This runoff is a major source of flooding and water pollution in urban communities worldwide.
• Impervious surfaces (roads, parking lots and sidewalks) are constructed during land development which results in high amount of surface runoff.
• It is mostly inorganic in nature with gasoline, motor oil, heavy metals, trash and other pollutants from roadways and parking lots.

Run-off from agricultural forms: 

• Agricultural Runoff is water from farm fields due to irrigation, rain, or melted snow that flows over the earth that can absorb into the ground, enter bodies of waters or evaporate.
• This runoff can contain organic pollutants like pesticides, sediment (soil particles), nutrients (phosphorus, nitrogen and potassium from fertilizers) and metals, which can contaminate sources of water.

Sewage effluents:

• Sewage, or domestic/municipal wastewater, is a type of wastewater that is produced by a community of people.
• It is characterized by physical, chemical and toxic constituents, and its bacteriologic status.
• It consists mostly of greywater (from sinks, bathtubs, showers, dishwashers, and clothes washers), blackwater (the water used to flush toilets, combined with the human waste that it flushes away), soaps and detergents, and toilet paper (less so in regions where bidets are widely used instead of paper). 
• Sewage effluents have the highest amount of organic pollutants along with bacterial contamination.

Industrial effluents:

• Industrial effluent is the wastewater produced by industrial activity.
• It includes wastewater produced from the manufacturing process or cleaning process.
• The composition of wastewater generated mostly depends on the nature of the industry.
• It is mostly inorganic in nature.

​Thus, the major source of water pollution is domestic sewage or dirty water, industrial effluent, silt and mineral oil.

Additional Information

Effects:

• Water pollution leads to excessive buildup of nutrients nitrogen and phosphorus in the water body called nutrient enrichment.
• Excess nutrient buildup leads to algal bloom in the water body eventually leading to eutrophication.