Water Quality and Pollution Quiz

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Questions and Answers

What is the biochemical oxygen demand (BOD) primarily associated with?

The demand placed on dissolved oxygen by pollutants in wastewater (correct)

The total oxygen produced by aquatic plants during photosynthesis

The oxygen consumption of aquatic life in natural habitats

The amount of dissolved oxygen in atmospheric air

Which of the following is NOT classified as an oxygen-demanding substance?

Tannins from tea leaves (correct)

Ammonia

Organic matter

Animal waste from food processing

What happens when dissolved oxygen levels in water drop below 5.0 mg/l?

Aquatic life experiences stress (correct)

Water becomes more polluted

Fish feed more actively

Aquatic plants proliferate rapidly

How does dissolved oxygen typically enter water bodies?

By diffusion from the surrounding air and through aeration Signup and view all the answers

Why is a high level of dissolved oxygen beneficial for community water supply?

It improves the taste of drinking water Signup and view all the answers

What is a potential health risk associated with high levels of Na in irrigation water?

Kidney disorders Signup and view all the answers

Which substance is primarily responsible for methemoglobinemia in infants?

NO3- Signup and view all the answers

What adverse effect can high Biological Oxygen Demand (BOD) levels have on aquatic environments?

Algal blooms Signup and view all the answers

Which of the following is NOT a potential impact of heavy metals on the environment?

Increased soil microbial activity Signup and view all the answers

What condition is primarily caused by the presence of protozoa such as Entamoeba histolytica?

Dysentery Signup and view all the answers

What is the purpose of preliminary treatment in wastewater management?

To remove large contaminants physically Signup and view all the answers

Which parameter is NOT tested when calculating the water quality index (WQI)?

BOD5 Signup and view all the answers

Which treatment stage directly reduces the organic load in wastewater?

Secondary treatment Signup and view all the answers

What is the tolerance limit for the biological oxygen demand (BOD5) in mg/L for sewage discharge in water systems?

30 mg/L Signup and view all the answers

How is total dissolved solids (TDS) measured in wastewater treatment?

In milligrams per liter (mg/L) Signup and view all the answers

Which of the following is a characteristic of tertiary or advanced treatment?

Removes dissolved and suspended materials Signup and view all the answers

What does the abbreviation 'COD' stand for in the context of wastewater quality?

Chemical Oxygen Demand Signup and view all the answers

During which stage of treatment is sludge generated?

Primary treatment Signup and view all the answers

What is the main purpose of filtration in a conventional water treatment system?

To remove particulate matter from water Signup and view all the answers

What is the diameter of a grain of fine sand used in filtration?

0.1 millimeter Signup and view all the answers

Which of the following contaminants can pose a challenge to filtration due to their size?

Viruses Signup and view all the answers

What is the primary function of the schumtzdecke in slow sand filtration?

To provide a habitat for bacteria Signup and view all the answers

What is the flow rate range of water in slow sand filtration?

0.1 to 0.3 cubic meters per hour Signup and view all the answers

Why are rapid sand filters more prevalent today compared to slow sand filters?

Their flow rates are higher and they require less space. Signup and view all the answers

How often are rapid sand filters typically cleaned?

Twice per day Signup and view all the answers

Study Notes

Module 3: Water Pollution

Water is essential for all living things
It comprises the majority of organisms' bodies
It's a habitat for numerous organisms
It helps regulate climate
It shapes the Earth's surface
It dilutes and degrades wastes

Water on Earth

About 97% of Earth's water is saltwater
Less than 1% of the planet's water is fresh water
Fresh water is unevenly distributed
In 2025, one-third of the human population will live in areas lacking fresh water

Types of Water Resources

Marine water (saltwater)
Surface water
Groundwater (freshwater)

Agricultural Use of Water

Agriculture accounts for 69% of global water consumption
Globally, agricultural demand will increase by an additional 19% by 2050
Water for irrigation is putting immense pressure on water storage.
Further expansion of irrigation and additional water withdrawal from rivers and groundwater is uncertain

Industrial Use of Water

Water is critical to many industrial processes
Manufacturing industries consume a significant portion of global industrial water consumption
Worldwide, industries use approximately 19% of total water consumption.
In industrialized countries, industries use more than half of the available water for human use

Domestic Use of Water

Domestic uses include drinking, cleaning, personal hygiene, gardening, cooking, and washing.
Domestic water use accounts for approximately 12% of total global water consumption
The increasing migration to urban areas puts a greater strain on water resources.

Hydropower

Electricity generated from water is called hydropower
It's one of the major renewable sources of electricity globally
Hydropower accounts for approximately 16% of the total global electricity generation
The leading hydropower generating countries are China, the US, Brazil, Canada, India, and Russia

Navigable waterways are used largely for transportation
Also for various recreational purposes, like boating, swimming, etc
These activities can affect water quality negatively and cause pollution

Water Resource Problems

Too much water (flooding)
Too little water (shortage)
Poor-quality water (contaminated water)

Pollution and Water Protection

Water pollution is a major concern globally
Governments are working to address this issue.
One of the greatest concerns is the discharge of untreated sewage into natural water sources
Sewage, sludge, garbage, and toxic pollutants are often dumped into water supplies (in many developing countries).
Non-point source pollution is a major contributor to this, including agricultural runoff and urban stormwater runoff

Sources of Water Pollution

Domestic wastes
Industrial wastes
Agricultural wastes, including pesticides and insecticides
Radioactive wastes

Domestic Water Sources

Domestic wastewater contains various pollutants, such as nutrients, oils, grease, detergents, biowastes, household chemicals, heavy metals, bathing and kitchen waste, salts, pathogens, and organic matter.

Causes of Water Pollution

Growing population increasing demand for water
Industrialization brings rapid development, but with environmental pollution concerns
Urbanization leads to the growth of population and industries near water sources—which deteriorates water quality

Nature of Modern Technology

Industries responsible for generating synthetic and non-biodegradable materials (plastics, chemicals, nitrogen fertilizers, detergents, synthetic fibers, petrochemicals, and environmentally harmful industries).
Increased production and disposability culture are major contributors to the issue of water pollution

Modern Agricultural Practices

Fertilizers (phosphates and nitrates) used in agriculture when applied carelessly can cause widespread damage to crops
The fertilizers may be carried into groundwater or surface water, due to leaching and storm runoff

Radioactive Wastes

Natural and manmade sources (atomic explosions, nuclear fallout).

Point Source and Non-Point Source Pollution

Point source pollution comes from a specific location (e.g., industrial discharge pipe).
Non-point source pollution comes from various diffuse sources (e.g., agricultural runoff, urban stormwater).

Changes in Surface Runoff

Before 1970, approximately 10% of stormwater became runoff
Currently, approximately 55% of stormwater is runoff
This is primarily attributed to increased development (75% or more of permeable soil area are now not permeable).

Stormwater Runoff

The greatest contributor to non-point source pollution, containing nutrients, metals, suspended solids, pesticides, hydrocarbons, and microorganisms, all contaminating the water bodies.

Types of Water Pollution

Surface water contamination (pollution from oceans, lakes, and rivers, often from land sources carrying pollutants).
Marine pollution (pollution involving various chemicals and waste from land sources).
Groundwater contamination (contaminants from landfills and septic systems making water unsafe for human use).
Thermal pollution (sudden increase/decrease in water temperature from human activities affecting local ecosystems.)

Major Types of Water Pollutants

Suspended solids
Biodegradable organics
Pathogens
Nutrients
Priority pollutants
Refractory organics
Heavy metals
Dissolved inorganics

Classification of Water Pollutants

Occurrence: Temperature, turbidity, color, suspended matter/floating matter
Nature: Inorganic, chemical, organic, biological, nuisance, and organisms.
Examples: Waste from industries, dyes and pigments, silt, sand, metals, and nitrites or phosphates

Concept of Water Quality

Water quality is determined by its suitability for various uses.
This includes drinking, hygiene, fisheries, irrigation, agriculture, industrial applications (cooling for power plants, etc.)

Water Quality Parameters

Many parameters affect water quality for various uses
Impacts on Industrial Water Use

Type of Pollutants: Oxygen-Demanding Substances

Dissolved oxygen is a crucial element needed to support aquatic life
Numerous pollutants present in wastewater create high demand for oxygen to break down organic matter

Dissolved Oxygen

Dissolved oxygen levels vary based on temperature
Lower dissolved oxygen levels negatively affect aquatic life.
High dissolved oxygen can also be a problem for businesses in some cases.

Biochemical Oxygen Demand (BOD)

The amount of oxygen required by aerobic organisms to break down organic material in water
Measured over specific periods
Indicative of the level of organic pollutants in water

Chemical Oxygen Demand (COD)

A measure of organic matter susceptible to oxidation by a strong chemical oxidant
Used to determine the level of organic pollutants in water

Oxygen Sag Curve

Shows the decrease in dissolved oxygen levels in water due to pollution

Pathogens

Infectious microorganisms are harmful to humans, carried in surface or groundwater.
Sewage carries various pathogens.
Human contact with contaminated water sources is a major route of infection

Nutrients

Nitrogen, carbon, and phosphorus are essential for living organisms
Excessive amounts can lead to algal blooms.
This disrupts photosynthesis in water, reducing oxygen levels.

Eutrophication

Excess nutrients encourage rapid algae growth
This depletes oxygen, harming aquatic life and causing odor problems.

Causes of Eutrophication

Fertilizers, untreated sewage, detergents, and industrial wastes contribute significantly to phosphorus and nitrogen levels in water bodies

Effects of Eutrophication

Significant biodiversity loss
Increased water toxicity
Depletion of aquatic life
Reduced water quality

Invasion of New Species

Eutrophication can alter the balance of an aquatic ecosystem
The balance shifts towards more adaptable species potentially outcompeting the previous inhabitants

Inorganic and Synthetic Organic Chemicals

Includes a vast range of harmful chemicals
Many are toxic to fish and aquatic life, and to humans

Thermal Pollution

A change in water temperature due to industrial activities or other human inputs affects water quality.
This affects oxygen levels and consequently the aquatic ecosystem

Drinking Water Standards

IS 10500: 2012: drinking water standards in India
Includes organoleptic and physical parameters (color, odour, pH, turbidity.)
Includes general parameters concerning substances undesirable in excessive amounts
Includes parameters concerning toxic substances
Includes radioactive substances

Calculation of Water Quality Index (WQI)

Uses selected water quality parameters
Weights assigned based on standards
Quality index calculated for each parameter
WQI values categorized for assessing water quality according to an index

Water Treatment

Processes for improving water quality for different uses

Indian Standards for Discharge of Sewage in Surface Waters

Provides permissible limits for various characteristics of the effluent (BOD5, COD, and TSS)

Water Treatment Plant-Surface Water Supply Diagram

Diagram showing the steps from preliminary treatment to distribution

Wastewater Treatment Scheme

Diagram indicating stages of wastewater treatment (Preliminary, Primary, Secondary, and Tertiary treatment)

Wastewater Treatment Processes

Preliminary treatment (physical process to remove large wastes).
Primary treatment (involves physical sedimentation).
Secondary treatment (physical and biological treatment to reduce organic pollutants).
Tertiary/Advanced Treatments

Preliminary Treatment

Process to remove large suspended solids

Grit Removal

Wastewater solids are also separated
Grit Removal process to remove large solids.

Primary Treatment

Removal of coarse solids in wastewater

Primary Sedimentation

Process in wastewater treatment plants
Removal of suspended solids by settling them in the tanks

Removal of Oil and Grease

Processes used to remove oil and grease from wastewater
Skimming, gravity separation and chemical addition

Coagulation and Flocculation

Methods used to remove suspended solids

Commonly Used Coagulants and Flocculants

Types of chemicals used in water treatment

Clarification

Removing suspended solids from treated water

Filtration

Removing suspended particles from water using filters

Slow Sand Filtration

Biological process using bacteria to remove pollutants

Rapid Sand Filtration

Filtration process using various sized filters

Equalization

Wastewater flows homogenized in tanks

Secondary Treatment

Reduction of organic matter (usually by biological methods)

Wastewater Treatment Plant Microorganisms

Microorganisms play critical roles in wastewater treatment

F/M Ratio

Food-to-Microorganism Ratio in wastewater treatment systems

Types of Secondary Treatment

Attached growth processes, suspended growth processes

A Trickling Filter

A bed of media to remove pollutants

Biotowers

Use of plastic media in towers to remove pollutants

Rotating Biological Contactor (RBC)

Use of rotating discs to remove pollutants

Suspended Growth Process

Microorganisms suspended in the wastewater to remove pollutants

Activated Sludge Treatment

A treatment process that includes aeration tanks and settling basins

Activated Sludge Process (ASP)

Wastewater treatment process using microorganisms in aeration tanks

Upflow Anaerobic Sludge Blanket Reactor (UASB)

Wastewater treatment process using microbial aggregates

Oxidation Ditch

Extended aeration suspended growth process

Lagoons

Treatment of wastewater using a shallow pond

Sequencing Batch Reactor (SBR)

Wastewater treatment cycle that involves filling, aeration, settling, decanting, and idling

The Use or Disposal of Wastewater Residuals and Biosolids

Processes for disposing of wastewater solids

Prior to Utilization or Disposal

Biological treatment techniques

Incineration

Burning of dried solids to reduce organic residuals

Biosolids and its Uses

Uses of biosolids as fertilizer and soil improvements, especially for lawn care, turf, and citrus groves.

Disinfection

Chemical and other methods to kill microorganisms in water

Chlorine

Widely used disinfectant for wastewater. Discussion of free vs. combined chlorine.

Chlorine Demand

Amount of chlorine needed in water treatment

Breakpoint Chlorination

Curve showing how chlorine dosage relates to chlorine demand in water bodies

Disadvantages of Chlorination

Byproducts of chlorine disinfection may negatively affect water and aquatic life

Ozone

Another method for disinfection

Ultraviolet Radiation

Treatment for water disinfection using UV radiation

Advanced Treatment/Tertiary Treatment

Various methods for advanced wastewater treatment and water purification

Membrane Filtration

Importance and different membrane processes

Classification of Membranes

Different types of membranes by pore size (Microfiltration, Ultrafiltration, Nanofiltration, Reverse Osmosis)

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Description

Test your knowledge on the biochemical oxygen demand (BOD) and its effects on water quality. This quiz covers essential concepts related to dissolved oxygen levels, irrigation water health risks, and wastewater management practices. Challenge yourself and learn more about the impact of pollution on aquatic environments.