Environmental Engineering MCQ Quiz - Objective Question with Answer for Environmental Engineering - Download Free PDF

Explanation:

Sludge Volume Index 

• Sludge Volume Index (SVI) is the volume occupied by 1 gram of suspended solids after 30 minutes of settling.

• It is an important parameter in the activated sludge process to assess the settling characteristics and health of the biological sludge.

 Thickening of Sludge

• Thickening involves increasing the solids concentration of sludge by allowing it to settle and compact, commonly performed in secondary clarifiers where biological solids settle.

 Additional Information Scum Removal

• Scum consists of floating materials such as oils and grease that rise to the surface in primary sedimentation tanks and must be removed by mechanical or manual skimming.

Recycling of Effluent

• In trickling filters, part of the effluent is often recycled to maintain hydraulic loading, improve contact time, and stabilize the biological film.

• This enhances treatment efficiency, especially under varying load conditions.

Explanation:

Salinity Reduction (Desalination)

• Salinity in water refers to the concentration of dissolved salts, primarily chlorides, sulfates, sodium, and other ions. Removing these requires advanced treatment processes capable of separating dissolved ions.

• Reverse Osmosis (RO) is a membrane-based process where water is forced under pressure through a semi-permeable membrane.

• It effectively removes dissolved salts, heavy metals, and other impurities.

• Widely used for desalination of seawater and brackish water.

• Electrodialysis uses ion-exchange membranes and electric potential to remove dissolved ions from water.

• Positively and negatively charged ions migrate through membranes to separate chambers, leaving behind desalinated water.

• Effective for saline groundwater and industrial wastewater.

 Additional InformationPrimary Treatment of Water

• Removal of Large and Settleable Solids
  Primary treatment involves physical processes like screening and sedimentation to remove floating debris, grit, and suspended solids. Large solids are first removed by bar screens, followed by grit chambers to eliminate heavier inorganic matter such as sand and gravel.

• Sedimentation for Suspended Solids
  In primary sedimentation tanks, water is held for several hours to allow heavier suspended particles to settle at the bottom as sludge, while lighter materials like oils and grease float to the surface for removal. This reduces the total suspended solids (TSS) load entering secondary treatment.

• Partial Reduction of Organic Load
  Though not designed to remove dissolved contaminants, primary treatment helps in reducing the organic load (BOD) by about 25–30%, making downstream biological processes more efficient. It also stabilizes the flow and composition of wastewater.

• Sludge and Scum Handling
  The settled sludge is collected and sent for further treatment like thickening or digestion. The floating scum, consisting of oils and grease, is skimmed off separately. Proper handling of these by-products is crucial to prevent blockages and maintain operational efficiency.

Explanation:

• Sullage refers to the wastewater that comes from kitchens, bathrooms, and wash basins.

• It generally contains soap, grease, detergents, and small food particles, but it does not contain human excreta.

• It is also called greywater — and is separate from the blackwater that comes from toilets.

Additional Information

• Garbage:
  Solid waste material — food scraps, paper, packaging — not liquid waste.

• Sewage:
  Combination of sullage + blackwater — it includes all domestic wastewater, including toilet waste (human excreta), kitchen, bath, and laundry waste.

• Discharge:
  General term for any outflow of water — could refer to treated effluent or natural water flow, not specific to household wastewater.

Explanation:

Montreal Protocol (1987)

• An international treaty to phase out substances that deplete the ozone layer.

• Focuses on controlling CFCs and other ozone-depleting substances.

Basel Convention (1989)

• Controls transboundary movement of hazardous wastes and their disposal.

• Prevents developed countries from dumping hazardous waste in developing countries.

Kyoto Protocol (1997, came into force in 2005)

• International agreement under the UNFCCC to reduce greenhouse gas emissions.

• First legally binding framework for global efforts to fight climate change.

Stockholm Convention (2001)

• Focuses on eliminating or reducing the release of persistent organic pollutants (POPs).

• POPs are chemicals that remain intact in the environment for long periods.

Additional Information

1. United Nations Framework Convention on Climate Change (UNFCCC) — 1992 (Rio Earth Summit)

• Established a global framework to combat climate change.

• Focuses on stabilizing greenhouse gas (GHG) concentrations to prevent dangerous human interference with the climate system.

• It is non-binding but sets the stage for legally binding agreements (like Kyoto Protocol and Paris Agreement).

• Recognizes the principle of Common but Differentiated Responsibilities — developed nations should take the lead in reducing emissions.

• Led to annual Conferences of the Parties (COP) — the primary international meeting on climate change.

2. Paris Agreement — 2015

• Successor to Kyoto Protocol under the UNFCCC framework.

• Aims to limit global warming to well below 2°C, preferably to 1.5°C, compared to pre-industrial levels.

• Unlike Kyoto, it involves both developed and developing countries — global participation.

• Countries submit Nationally Determined Contributions (NDCs) — voluntary targets to cut GHG emissions.

• Encourages adaptation, climate finance, technology transfer, and capacity building.

• Seen as a landmark global effort toward combating climate change.

Explanation:

• To ensure reliability, pipelines and pumping systems are designed for the greater of Peak Hourly Demand or Coincident Draft — so the system will not fail even under the highest expected load.

• The distribution system of water supply is the network of pipelines that delivers water to consumers.

• It must be designed to handle fluctuating water demands — during different times of day, seasons, or emergencies.

 Additional Information

Peak Hourly Demand (A):

• The maximum water demand occurring during the most critical hour of the day.

• This often happens during mornings or evenings when residential and commercial use is at its highest.

• The system must handle this peak to avoid pressure drops or shortages.

Coincident Draft (B):

• It represents the simultaneous maximum water demands of various parts of the system (or zones).

• Different areas may have peak demands at the same time — the system must also handle this scenario.

Average Daily Demand:

• The average amount of water used per day.

• Used for estimating overall supply but not sufficient for designing pipelines and pumps, which must handle peaks.

The correct answer is Filtration.

Key Points

Filtration

• Filtration is a process used to separate solids from liquids or gases by using a filter medium that allows fluid to pass through but not solid. 
• Filtration can be mechanical-biological or physical. 
• It does not help in disinfecting water. 
• If you want to disinfect the water you can boil it or you can use alum for chlorine tablets. 

Boiling

• Boiling is used to kill pathogenic bacteria, viruses, and protozoa. 

Chlorination

• Chlorine kills a large variety of microbial waterborne pathogens.
• Chlorination is the process of adding chlorine to the water to disinfect it and kill pathogens. 
• Amount of chlorine required for water disinfection around 1-16 milligrams per litre of water.

Coagulation

• Alum acts as an electrolyte that helps in settling the suspended matter in water.
• The process of adding alum to disinfect water is called coagulation. 

Concept:

• Water softening: It is the process of hardness removal from the water. It is caused by multivalent cation and affects water quality.
   
• Lime soda method: It is a water softening method in which lime and soda ash are added to the water, which causes the precipitation of multivalent cation as CaCO3.
• Precipitation of CaCO3 occurs only when the pH of water is greater than 9, so in case of less pH alkalinity is added to the water. In this process small amount of Ca2+ and Mg2+ precipitates very late, which will create incrustation in the pipe, so to avoid this recarbonation is done to dissolve back this small amount of cation.
• Due to this, the method does not give zero hardness.
   
• Ion Exchange Process: Ion-exchange resin, (zeolite) exchanges one ion from the water being treated for another ion that is in the resin (sodium is one component of softening salt, with chlorine being the other). Zeolite resin exchanges sodium for calcium and magnesium. It can produce water with zero hardness.

Explanation:

The odour characteristic is used for classifying odour of a given water sample as per IS 3025 (part-5) 1983 as follows:

1. Degrees of sweetness

2. Degrees of pungency

3. Degrees of smokiness

4. Degrees of Rottenness

Concept:

Odour and taste are expressed by threshold odour number (T.O.N.) as it represents the dilution ratio at which odour can not be detected.

where A = Volume of water sample undiluted 

B = volume of distilled water required to be added to remove the odour.

Calculation:

Given,

A + B = 250 ml

A = 25 ml

T.O.N. = 10

Mistake Points

• Generally in these question volume of water to be added (B), is given.
• But In the question, it is given " sample was diluted to ", which means that the final volume of the sample after dilution(A+B) is given 

Concept:

The peak flow can be considered as 1.5 times the annual average daily flow.

For a design of the treatment facility, the peak factor is considered as 1.5 times the annual average daily flow.

The minimum flow passing through sewers is also important to develop self-cleansing velocity to avoid silting in sewers. This flow will generate in the sewers during late night hours. The effect of this flow is more pronounced on lateral sewers than the main sewers.

Sewers must be checked for minimum velocity as follows:

Minimum daily flow = 2/3 Annual average daily flow

Minimum hourly flow = 1/2 Minimum daily flow

Minimum hourly flow = 1/3 Annual average daily flow

Followings are the classification of secondary treatment units:

Explanation:

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

Followings are the classification of secondary treatment units:

As per IS 10500: 2012, the following are the various permissible limits for different parameters:

Fluoride or fluorine deficiency is a disorder that may cause increased dental caries (or tooth decay) is the breakdown of dental tissues by the acidic products released by the bacterial fermentation of dietary carbohydrates.

Excess of nitrates is harmful to infants and causes Methemoglobinemia or Blue baby disease.

is toxic to many organs and tissues including heart, kidney, bones, intestines, reproductive system and nervous system. Excess lead causes anemia.

Concept:

The population after n^th decade by using Arithmetic mean Method is given as:

Where

P is the Present Population

N is no of decades of which population is to be calculated

X̅ is the average increase in population.

Calculation

The population at end of 2011 i.e. after 3 decodes from 1981.

Explanation:

Noise pollution

• It is a major issue in today’s urban areas. From factories to vehicles, from machinery to daily equipment, everything produces a noise that is having a significant impact on the ambient environment as well as the health and well-being of humans.
• Recognizing the harmful effects of noise, the Indian government included measures to abate noise pollution under the Environment Protection Act, 1986. Noise pollution was one of the categories being addressed under this Act. However, in the late 1990s, the government decided to come out with separate legislation solely focusing on noise pollution. Thus was born, Noise Pollution (Regulation and Control) Rules, 2000.