Test: Environmental Engineering - 1 - Civil Engineering (CE) MCQ

• Radial Settling Tank (Thickener) using Coagulant (Lime & Ferrous Sulphate):




• Radial settling tanks, also known as thickeners, are commonly used in wastewater treatment plants to separate suspended solids from liquid.


• Coagulants such as lime and ferrous sulphate are added to the waste water to help the suspended solids clump together and settle at the bottom of the tank.


• The settling process allows the solids to be separated from the liquid, making it easier to remove them from the wastewater stream.


• This method is effective in removing suspended solids present in the waste water generated in blast furnace gas cooling and cleaning plants.

• Cancer risk: Working in cement plants and limestone quarries can expose individuals to carcinogens such as silica dust, which can increase the risk of developing cancer.



• Asthma: Exposure to dust and particulate matter in these environments can lead to respiratory issues like asthma due to irritation and inflammation of the airways.



• Silicosis: Silicosis is a lung disease caused by inhalation of crystalline silica dust, which is commonly found in cement plants and quarries. This condition can lead to scarring of the lungs and breathing difficulties.



• Fluorosis: Fluorosis is a bone disease caused by excessive intake of fluoride, which may be present in the water or materials used in cement production. This condition can lead to weakened bones and joint pain.

Overall, the combination of exposure to hazardous substances and poor working conditions in cement plants and limestone quarries can significantly increase the risk of developing various diseases among workers.

• Cyclone Separator: A cyclone separator is a device used to separate particles from a gas or liquid stream without the use of filters.


• Centrifugal Force: The operating principle of a cyclone separator is based on the action of centrifugal force on dust particles.


• Centrifugal Separation: When the gas or liquid stream containing particles enters the cyclone separator, it is forced to move in a circular motion.


• Particle Separation: Due to the circular motion, the particles experience centrifugal force, causing them to move towards the outer wall of the cyclone separator.


• Particle Collection: The particles are then collected at the bottom of the cyclone separator, while the clean gas or liquid exits through the top.


• Efficiency: Cyclone separators are effective in removing large particles from the stream, making them popular in industries such as mining, food processing, and air pollution control.

• Particulates (< 1μm size): These are tiny particles that are less than 1 micron in size.


• Remaining suspended in air indefinitely: These particulates do not settle down and remain suspended in the air for a long time.


• Transported by wind currents: These particulates are carried by wind currents over long distances.


• Called aerosols: Particulates that fit the above description are known as aerosols.

• Definition: Maximum allowable concentration of CO₂ in air refers to the highest level of carbon dioxide that is considered safe for humans to breathe in a working environment.



• Importance: Monitoring CO₂ levels is crucial as high concentrations can lead to health issues such as headaches, dizziness, and difficulty breathing.



• Regulations: Different organizations and countries have set different standards for the maximum allowable concentration of CO₂ in air to ensure the safety of workers.



• ANSI/ASHRAE Standard 62.1: According to this standard, the maximum allowable concentration of CO₂ in air for safe working is 5000 ppm (parts per million).



• Choosing the Correct Answer: When given options, it is important to select the value that aligns with the established standards and regulations to ensure a safe working environment.

• Tolerable limit of nitrogen oxides in air refers to the maximum concentration of nitrogen oxides that can be present in the air without causing harm to human health or the environment.


• The standard limit for nitrogen oxides in air is typically measured in parts per million (ppm).


• The tolerable limit of nitrogen oxides in air is 5 ppm.


• This means that if the concentration of nitrogen oxides in the air exceeds 5 ppm, it can have negative effects on human health and the environment.


• Therefore, it is important to monitor and control the levels of nitrogen oxides in the air to ensure that they remain below the tolerable limit.

• Ion Exchange Process: This process is effective in removing iron and manganese from water by exchanging ions in the water with ions attached to a resin. However, this process is not suitable for high concentrations of these pollutants.



• Oxidation followed by Settling & Filtration: Oxidizing iron and manganese converts them into a solid form that can be easily removed through settling and filtration. This process is commonly used for removing these pollutants from water sources.



• Lime Soda Process or Manganese Zeolite Process: These processes involve the addition of lime or soda ash to precipitate iron and manganese, followed by filtration. Manganese zeolite is a specific media used for removing manganese from water efficiently.



• Chlorination: Chlorination is not effective in removing iron and manganese from water. While chlorine can oxidize these pollutants, it does not facilitate their removal through settling or filtration processes.

Therefore, among the given options, chlorination is not a suitable method for removing iron and manganese present as pollutants in water.

• Disinfection: Chloramines are effective disinfectants that can kill harmful bacteria, viruses, and other microorganisms in water. They provide long-lasting protection against pathogens, ensuring the safety of the water supply.



• Taste & Odour Control: Chloramines help improve the taste and odour of water by reducing the presence of organic compounds that can cause unpleasant smells and flavors. This results in a more palatable drinking water for consumers.



• Weed Control in Reservoirs: Chloramines can also help control the growth of algae and other aquatic plants in reservoirs and water bodies. By inhibiting the growth of weeds, chloramines can prevent clogging of water pipelines and filters.



• Removal of Permanent Hardness: While chloramines are not primarily used for removing permanent hardness from water, they can help in controlling the formation of scale deposits in pipelines and equipment. This can indirectly contribute to reducing the effects of hardness in water systems.

Overall, the use of chloramines in water chemical treatment plants is crucial for ensuring proper disinfection, taste & odour control, and maintenance of water quality standards.

• SO₂: Sulfur dioxide is the common pollutant emitted from metallurgical smelters, thermal power plants, and cement plants.


• Metallurgical Smelters: These facilities release sulfur dioxide during the smelting process of ores to extract metals.


• Thermal Power Plants: Burning coal or oil in thermal power plants can produce sulfur dioxide as a byproduct of combustion.


• Cement Plants: The calcination process in cement plants releases sulfur dioxide due to the decomposition of limestone.


• Health Effects: SO₂ can have harmful effects on human health, causing respiratory issues and aggravating conditions like asthma and bronchitis.


• Environmental Impact: Sulfur dioxide emissions contribute to acid rain, smog formation, and air pollution.

• Adsorption of H₂S: Adsorption is a process where molecules of a substance adhere to the surface of a solid.


• Removal of H₂S: H₂S can be removed from a gaseous stream by adsorption on certain materials that have a high affinity for sulfur compounds.


• Bog Iron: Bog iron is a type of iron ore that is formed in bogs or swamps. It has been found to be effective in adsorbing H₂S due to its high iron content.


• Advantages of Bog Iron: Bog iron is a natural material, environmentally friendly, and cost-effective for H₂S removal compared to other methods.


• Process: The gaseous stream containing H₂S is passed through a bed of bog iron where the sulfur compounds are adsorbed onto the surface of the material.


• Regeneration: Once the bog iron is saturated with H₂S, it can be regenerated by heating or other methods to release the sulfur compounds for disposal or further use.

• Idle running: When the car is idling, the engine is running at a low speed and the combustion process is not as efficient. This leads to a build-up of unburned fuel, resulting in a higher carbon monoxide content in the exhaust gas.


• Acceleration: During acceleration, the engine is working harder to increase speed, leading to a more complete combustion of fuel and a lower carbon monoxide content in the exhaust gas.


• Cruising: When the car is cruising at a constant speed, the engine is operating at a steady state which allows for a more efficient combustion process. This results in a lower carbon monoxide content in the exhaust gas compared to idle running.


• Deacceleration: During deceleration, the engine is not actively burning fuel, which can lead to a decrease in carbon monoxide emissions in the exhaust gas.

Therefore, during idle running, the carbon monoxide content in the exhaust gas is maximum due to the inefficient combustion process at low engine speeds.

• When water flows over rocks and waterfalls, it comes into contact with the air, allowing for oxygen to be naturally dissolved into the water.


• This process helps to replenish the oxygen levels in the water stream, especially in areas where there is little to no pollution.

• Algae are photosynthetic organisms that use sunlight to produce oxygen through the process of photosynthesis.


• When algae are present in a water stream, they can contribute to the replenishment of dissolved oxygen through their photosynthetic action.

• Combining the natural aeration of the water stream with the photosynthetic action of algae can greatly help in replenishing dissolved oxygen levels in a polluted water stream.


• These processes work together to improve the overall water quality and support aquatic life in the ecosystem.

Effects of Inhalation of Lead Compounds from Automobile Exhaust:

• Blood Poisoning: Lead compounds can lead to blood poisoning when inhaled, as they can interfere with the production of red blood cells.



• Anaemia: Chronic exposure to lead compounds can cause anaemia by inhibiting the body's ability to produce hemoglobin.



• Nervous System Disorder: Lead poisoning can also affect the nervous system, leading to symptoms such as headaches, memory loss, and confusion.



• Overall Impact: When combined, the effects of blood poisoning, anaemia, and nervous system disorders can have severe consequences on an individual's health and well-being.

Therefore, the inhalation of lead compounds present in automobile exhaust, particularly from leaded petrol, can have detrimental effects on the body, impacting various systems and functions.

• Reynold Stresses: Aerodynamic noise in valves is primarily caused by Reynold stresses, which are fluctuations in velocity and pressure in the gas flow that create turbulent eddies.


• Shear Forces: Shear forces in the gas flow also contribute to aerodynamic noise, as they cause friction and turbulence in the flow, leading to noise generation.

• Reynold stresses and Shear Forces: The combined effect of Reynold stresses and shear forces results in turbulent gas flow, which is the main source of aerodynamic noise in fluid flow control valves.

• Minimizing Turbulence: To reduce aerodynamic noise in valves, measures can be taken to minimize turbulence in the gas flow, such as using smoother surfaces and streamlined designs.


• Proper Valve Sizing: Ensuring proper valve sizing and selection can also help in reducing aerodynamic noise by optimizing the flow characteristics.


• Regular Maintenance: Regular maintenance of valves is essential to prevent any build-up or obstructions that can lead to increased turbulence and noise.

• Insufficient supply of combustion air and insufficient time for combustion: When there is not enough air for the fuel to burn completely, smoke is produced as a byproduct of incomplete combustion.


• Poor quality of fuel and improper mixing of fuel & combustion air: Low-quality fuel or improper mixing of fuel and air can lead to inefficient combustion, resulting in the generation of smoke.


• Poor design & overloading of furnace: If the furnace is not designed properly or if it is overloaded, it can lead to incomplete combustion and the production of smoke.

• Ensure an adequate supply of combustion air to facilitate complete combustion.


• Use high-quality fuel and ensure proper mixing with combustion air.


• Regular maintenance of the furnace to prevent overloading and ensure efficient operation.

• Fluorosis: Fluorosis is a bone disease caused by the excessive accumulation of fluoride in the body.

• Hydrogen Fluoride: High concentrations of hydrogen fluoride in the atmospheric air are the main cause of fluorosis.

• When individuals are exposed to high levels of hydrogen fluoride through inhalation or ingestion, it can lead to the development of fluorosis.


• Excessive intake of fluoride can interfere with the normal development and maintenance of bones, leading to skeletal fluorosis.


• Fluoride can accumulate in bones over time, causing them to become weak, brittle, and prone to fractures.


• Long-term exposure to high levels of fluoride can also affect teeth, leading to dental fluorosis.

• Preventing fluorosis involves reducing exposure to sources of fluoride, such as avoiding drinking water with high fluoride levels and using fluoride-free dental products.


• Regulating industrial emissions and ensuring proper disposal of fluoride-containing waste can also help prevent environmental contamination with fluoride.

• Definition: Threshold Limit Value (TLV) is the maximum allowable concentration of a pollutant in air.


• Safe Limit for SO₂: The safe limit for SO₂ in air is 5 parts per million (ppm).


• Explanation: This means that the concentration of SO₂ in the air should not exceed 5 ppm to ensure safety for human health and the environment.


• Importance: Adhering to TLVs helps in preventing health issues and environmental damage caused by exposure to harmful pollutants like SO₂.


• Monitoring: Regular monitoring of air quality is essential to ensure that pollutant levels, including SO₂, remain within safe limits.

• Definition: Carcinogens are substances that can cause cancer in living tissues.


• Mechanism: Carcinogens can damage the DNA in cells, leading to uncontrolled cell growth and tumor formation.


• Types of carcinogens: Carcinogens can be found in various sources such as tobacco smoke, UV radiation, certain chemicals, and pollutants.


• Effects: Exposure to carcinogens can increase the risk of developing various types of cancer, including lung, skin, bladder, and liver cancer.


• Prevention: It is important to minimize exposure to known carcinogens by following safety guidelines, wearing protective equipment, and avoiding smoking and excessive sun exposure.

Therefore, exposure to chemicals having carcinogenic properties can lead to the development of cancer in individuals.

• CO: Carbon monoxide is a toxic gas produced during the combustion of carbon-based fuels.


• CO₂: Carbon dioxide is a greenhouse gas that contributes to global warming and climate change.


• SO₂: Sulfur dioxide is a harmful gas produced when sulfur-containing fuels are burned, leading to acid rain and respiratory issues.

Explanation:

• The iron and steel industry is a major source of air pollution, releasing significant amounts of CO, CO₂, and SO_{2> into the atmosphere.}


• These pollutants can have serious environmental and health impacts, affecting air quality and contributing to climate change.


• Efforts are being made to reduce emissions from this industry through the use of cleaner technologies and better pollution control measures.

Control of Scale Formation in Boiler

• Preheating of Feed Water: Preheating the feed water helps in reducing the chances of scale formation as it increases the solubility of minerals in water and prevents their precipitation.


• Reduction in Hardness, Silica & Alumina in Feed Water: Hardness, silica, and alumina are major contributors to scale formation. By reducing the levels of these impurities in the feed water, the formation of scale can be controlled.


• Keeping the pH Value of Feed Water Just Below 7: Maintaining a slightly acidic pH level in the feed water helps in preventing the precipitation of minerals and reduces the formation of scale.


• Eliminating H₂S in Feed Water: Hydrogen sulfide can react with minerals in water to form scale. Eliminating H₂S from feed water can help in controlling scale formation.

By following these measures, the scale formation in the boiler can be effectively controlled, leading to improved efficiency and longer lifespan of the boiler.

• Jet engine with afterburner: Jet engines with afterburners produce extremely high levels of noise due to the added fuel injection and combustion in the afterburner section.


• Distance of about 100 metres: At a distance of 100 meters, the noise level is still significantly high due to the powerful nature of the jet engine with afterburner.


• Noise level: The noise level heard at a distance of about 100 meters from a jet engine with afterburner is approximately 170 decibels.


• Decibel scale: Decibels are a logarithmic unit used to measure sound intensity. An increase of 10 decibels represents a 10-fold increase in sound intensity.


• Comparative noise levels: To put this into perspective, normal conversation is around 60 decibels, a rock concert is around 120 decibels, and a jet engine without afterburner is around 140 decibels.

• Definition: TLV stands for Threshold Limit Value, which is the maximum concentration of a substance that a person can be exposed to without adverse effects.



• TLV of Mercury in Potable Water: The TLV of mercury in potable (drinking) water is about 0.001 ppm.



• Options:
  
  
  
  • A: 0.001
  
  
  • B: 0.1
  
  
  • C: 1
  
  
  • D: 5
  
  
  
  



• The correct answer is A: 0.001 ppm.

• High Efficiency: Activated carbon adsorption is a highly effective method for removing organic contaminants present in low concentrations, such as less than 200 mg/litre. It has a high adsorption capacity and can effectively remove a wide range of organic pollutants.


• Chemical Structure: Activated carbon has a porous structure that provides a large surface area for adsorption. This allows the carbon to trap organic molecules and remove them from the water.


• Adsorption Process: In the adsorption process, organic contaminants in the water are attracted to the activated carbon surface and adhere to it. This effectively removes the contaminants from the water, leaving it clean and safe for consumption.


• Regeneration: Activated carbon can be regenerated by heating it to high temperatures, which removes the adsorbed contaminants. This makes it a cost-effective and sustainable method for water treatment.


• Cost-Effective: While activated carbon adsorption may require initial investment in equipment and maintenance, it is a cost-effective method for removing organic contaminants in low concentrations over the long term.

• Definition: Photochemical smog is a secondary air pollutant formed when sunlight reacts with primary pollutants like nitrogen oxides and volatile organic compounds in the atmosphere.


• Formation: Nitrogen dioxide and volatile organic compounds from vehicle emissions and industrial processes undergo chemical reactions in the presence of sunlight to form ground-level ozone and other harmful pollutants.


• Effects: Photochemical smog can lead to respiratory issues, eye irritation, and damage to plants and ecosystems. It also contributes to the formation of acid rain and poses a risk to human health.


• Control Measures: To reduce photochemical smog, measures like controlling emissions from vehicles and industries, promoting the use of cleaner fuels, and implementing stricter air quality regulations can be implemented.