Water pollution 4.4

What is pollution

The addition of substance or agent to the environment by human activity at a greater rate than can be rendered harmless by the environment and has appreciable effect on organisms

Types of pollution

• Matter

• Energy

• Living organisms

What is water pollution

occurs when harmful substances contaminate water bodies, degrading their quality and harming organisms

How many people does water pollution kill per day

14 000

How many people don’t have access to clean drinking water?

½ billion

Types of water pollution

• Anthropogenic/natural

• direct/indirect

• organic/inorganic

• point source/ non point source

Point source pollution example and advantage

• Factory discharges

• Easier to maintain

Non-point source pollution example and disadvantage

• Agricultural runoff

• Diffuse - hard to control

• Responsibility is shared - greater effort to enforce change

Sources of water pollution

• Agricultural runoff

• Sewage

• Industrial and domestic discharges

How does agricultural runoff cause water pollution

• runoff carries fertilisers, pesticides, sediment

• fertilisers - rich in nitrates and phosphates - algae bloom - eutrophication

• Pesticides accumulate in tissues of non targeted species and increase concentration up the food chain (biomagnification)

• Sediments increase turbidity - less light

How does sewage contribute to water pollution

• Enters rivers

• bacteria decompose organic matter = oxygen depletion

• pathogens in sewage = cholera

Examples of Industrial discharges and their effects

• toxic chemicals

• oil spills

• heavy metals - mercury

• disrupts aquatic life

What is plastic

• synthetic polymer made from petrolium

• useful properties = widely used

• non biodegradable

Microplastic

diameter less than 5mm

Nano plastic

diameter less than 1 micrometers

How many tonnes of plastic enter ocean annually

14 million tones

What are gyres and how are they formed

• large circular systems that collect floating material into garbage patches

• formed by ocean currents

How plastic turns into microplastic?

• Plastic pollution starts on land

• carried by rivers and wind to the oceans

• waves and UV break down

Impacts of plastic pollution

• larger pieces entangle animals

• Ingestion of microplastic - consumed by plankton = bioaccumulation and biomagnification, pass chemicals up the food chains = disrupts hormonal balance

• Beach pollution - less money

Great Pacific Garbage Patch

15 million km2, North Pacific Gyre

3 types of management strategies

• Altering human activity

• Reduce release of pollution

• Restoring ecosystems and removing pollutants

Example of plastic pollution managment strategies

• Education

• Social media

• Promoting circular economy

• Ban of single use plastics

• Non-plastic alternatives

• Barriers

• Beach clean up

• Bioremediation - bacteria/fungi to degrade plastics - under research

• Improving recycling infrastructure

What is water quality

Measure of chemical, biological and physical characteristics of water, determining its sustainability for supporting life and human use

What is water quality INDEX

• combines water quality parameters into a single value

• scaled from 1 to 100

• used to communicate results easy

Methods of assessing water quality

• Direct - measures the abiotic factors

• indirect - measures indicator species or biochemical oxygen demand

Examples of direct measures

• Disolved oxygen - probes

• pH - probes

• Temperature (affects OD, metabolic rates, species distribution) - probes

• Turbidity - turbidity meter/secchi disk (depth visibility test

• Nutrient concentration - calorimetric test kits (high conc = sewage discharge/agricultural runoff)

• Metal concentration - magnetic resonance analyser

Indicator species

• living organisms whose presence/absence gives information about an ecosystem

• Creates biotic index used to see the effect of pollutant on the community

Indicator species - method

• biotic index/indicator species

• sample macroinvertebrates in the stream

• identify the species present and what they indicate

Advantages of direct methods

• more accurate measure

• quick, cheap

• Probes reduce risk of direct contact with pollutant

• gives quantitative measurements

• allows to identify the actual pollutant

Advantages of indirect methods

• you can see impact on biodiversity

• shows impact of multiple pollutants on habitat

• no expensive equipment needed

Disadvantages of indirect methods

• cannot identify the actual pollutant

• cannot identify the source of pollution

• subjective

What is Biochemical Oxygen Demand

• measures the amount of oxygen required by aerobic microorganisms to decompose organic matter in water

What does high BOD indicate

• high organic pollution

• Low dissolved oxygen

• Hypoxic conditions - sensitive species dies and tolerant species survive

• poor water quality

What doe low BOD indicate

• clean water with little organic matter

Method of BOD sampling

• Measure initial dissolved oxygen

• Keep sample in the dark for 5 days at constant temp 20

• measure DO again

• take the difference of 2 measures

Factors affecting BOD

• Temperature - high temp - more microbial activity - high oxygen use

• Organic matter - more waste means more food for microbes = higher microbial population - higher oxygen demand

• Flow rate - high BOD in stagnant water due to reduced aeration

Eutrophication is

• The addition of nutrients , particularly nitrates and phosphates to a body of water, leading to excessive growth of algae and aquatic plants

Process of eutrophication

1. Nutrient enrichment

2. algae bloom

3. light limitation

4. plant death

5. plants decompose, consuming dissolved oxygen

6. oxygen depletion - hypoxia/anoxia

7. biodiversity loss - anaerobic bacteria dominate

8. toxic gas production

Causes of eutrophication

• detergents

• fertilisers

• sewage discharges

• topsoil erosion

Impacts of eutrophication

1. Fisheries decline - hypoxia kills fish or causes migration

2. Looks unpleasant - reduces recreational activities

3. cyanobacteria - releases toxins that contaminate water, health impacts

4. loss of biodiversity

Managing eutrophication - ALTERING HUMAN ACTIVITY

• Use alternatives to fertilisers and detergents that don’t cause eutrophication

• Use organic fertilisers that release nutrients slowly

Managing eutrophication - REDUCING RELEASE OF POLLUTANTS

• wastewater treatment to remove nitrates and phosphates

• regulations - environmental law

• wetlands restoration to absorb excess nutrients

Managing eutrophication - REMOVING POLLUTANTS

• dredging

• aeration

• chemical treatment

• restock flora and fauna

How can we use invertebrates to identify pollution in freshwater rivers

• different species - varying tolerance to pollutants

• presence/absence of specific group indicated overall health of an ecosystem

Why buffer zones important in eutrophication reduction?

They intercept agricultural runoff before it reaches water bodies, reducing nutrient input

How does pumping air help restore eutrophicated water bodies

increases oxygen levels, helping aquatic organisms survive and decompose organic matter