Fresh water resources and water supply - unit 3

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Fresh Water resources

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Global Overview

 _{While 67% of Earth’s surface is covered by}

water, only less than 2.7% of global water is freshwater. Most of the freshwater

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Over two thirds of the earth's surface is covered with water, 97.2% of which is contained in the five

oceans. The Antarctic ice sheet, containing 90% of all fresh water on the planet, is visible at the bottom.

Atmospheric water vapour can be seen as clouds,

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Volume of water stored in

the water cycle's reservoirs

Reservoir Volume of water

(106 km³)

Percent of total

Ocean 1370 97.25

Ice caps & glaciers 29 2.05

Groundwater 9.5 0.68

Lakes 0.125 0.01

Soil Moisture 0.065 0.005

Atmosphere 0.013 0.001

Streams & rivers 0.0017 0.0001

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Scarcity of fresh water

 _{On a global basis, fresh water is a}

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Water consumption for food

production (I)

 _{Meat production use a lot of water when}

compared to growing food crops.

 _{A shift in food consumption pattern toward}

more meat consumption will cause a

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Water consumption for food

production (II)

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Competing water uses (I)

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Competing water uses (II)

 _{Industrialized / developed countries tend to}

use more water in their industrial production.

 _{Other countries tend to use more water for}

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Fresh Water supply

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Problems related to Water crisis

 Inadequate access to safe drinking water by

over 1.1 billion people

 Groundwater overdrafting leading to

diminished agricultural yields

 Overuse and pollution of water resources

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Threats to fresh water resources

 _{Climate change causes change in}

frequencies of droughts and floods.

 _{Depletion of aquifers caused by}

over-consumption as a result of population growth.

 _{Pollution and contamination by sewage,}

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Distribution of population and

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Desalination of sea water as

fresh water supply

 _{Desalination of sea water can be done either}

via distillation or membrane process.

 _{Both process requires large amount of}

energy and thus costly, which means

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Key Characteristics of Arctic

Freshwater

 _{Drastic cycles in lakes and rivers each year}

– _{Thick or solid ice in winter}__{high water flow in spring (can be}

destructive)

 _{In areas dominated by vegetation, freshwater carries high}

concentrations of dissolved organic carbon (DOC)

– _{E.g. humic and fulvic acids (colour the water)}

 _{Supports an array of flora and fauna in sediment and water column}

(bacteria, protists, algae, micro-invertebrates)

 _{Essential habitat for freshwater fish (few in Arctic), anadromous fish,}

waterfowl, mammals

 _{Part of the freshwater food web that recycles carbon, nitrogen,}

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Overview

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Concepts

Acid rain

 Rainfall with a pH of less than 7.0 (in practical

terms, <5.0).

 Rain + Sulphur Dioxide  _{Same as acid deposition}

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Concepts

Nutrients

 As a pollutant, any element or compound, such as

phosphorous or nitrogen, that fuels abnormally high organic growth in aquatic systems (i.e.

eutrophication).

 As a fertilizer, any element or compound, principally

P, N, K, S, that are limited in availability, hence influence plant growth (e.g. algae) in water

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Concepts

Effluents

 _{The sewage or industrial liquid waste that is}

released into natural water by sewage

treatment plants or structures to treat industrial water (including mine water)

Receiving waters

 _{A river, lake, ocean, etc., into which waste}

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Drinking Water in the North

Issues

 Wells for extracting ground water is not an

option

 Underground water lines in permafrost require

insulation; installation of such infrastructure is a challenge

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Sanitation of Water

Inadequate sanitation may lead to:

 Gastrointestinal illness  _{Hepatitis A}

 Bronchitis  Meningitis

 _{Other bacterial infection}  Skin and eye diseases

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Concepts

Drinking Water:

 _{Water intended for human consumption but}

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Best Practices

 _{Prevention of the contamination of water sources}

(lakes, rivers, streams, and groundwater sources)

 _{Treatment of water}

 _{Proper maintenance of water distribution systems}  _{Regular monitoring of drinking water}

 _{Public education and awareness (especially for “in}

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Water Supply

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Water Supply

Components

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Water Supply

Distribution System

 _{Primary Feeders}

– _{Large pipes 400mm (16”)}

– _{Brings large amounts of water to different}

points of a water system

 _{Secondary Feeders}

– _{Intermediate pipes 300mm (12”)}

– _{Pipes that form a grid between the primary}

pipes

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Water Supply

Distribution System

 _Distributors

– _{Grid of smaller mains 200mm (8”) supplying}

hydrants and blocks

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Water Supply

Hydrants

33

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Water Supply

Hydrant Colour Codes

 _{Class AA –}_{Light blue}

5,000 LPM (1,500 gpm) or greater

 _{Class A –}_Green_3,785

– 5675 LPM (1,000-1,499 gpm)

 _{Class B –}_Orange

1,900-3780 LPM (500-999 gpm)

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Water Supply

Hydrant Colour Codes

 _{Class C –}_Red _less

than 1,900 LPM (500 gpm)

 _{Dead End– Black}

Sttipe or Grey – not reliable

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Water Supply

Hydrants

Locations

 _{90m (300 ft) in high value areas}

Basic Rule:

 _{Near each street intersection}

Pre-Plan your areas

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Water Supply

Pressures



Static

– _{Water is not moving. It is the potential}

energy available to force water through a pipe.



Normal Operating Pressure

– _{The normal pressure found in a}

distribution system during a period of normal consumption

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Water Supply

Alternative Sources

 _{Yard Hydrants}  Hose Hydrants  _{Draft Sources}  _{Cisterns/Pools}

 _{Rivers/Lakes/Ponds}  _{Ditches/Creeks}

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Water Supply

Rural Water Supply

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Water Supply

Considerations

 _{Resistance or friction loss in municipal}

systems

 _Corrosion

 _{Chemicals in water}  _Sediment

 _{Pipe size and length}  _{Water hammer}

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Water Supply

Hydrants

41 •Open and Close Slowly

•Open or Close Fully

•Drain Completely

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Waste Water

Sewage

 _{Liquid waste from toilets, baths and showers,}

kitchens, that is disposed via sewers, trucking, or on site treatment systems

Industrial Waste Water

 _{Waste water from industries of mines. Generally}

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Treatment Stages

 Primary: Mechanical treatment to reduce

coarse solids, sand and dirt, oils and grease

Note: Ideal as pre-treatment or for treating “surface” water (e.g. street water)

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Treatment Stages

 _Secondary_{: Treatments designed to degrade}

biological content of sewage (e.g. human waste, food waste) through aerobic biological processes

Note: Require aeration for bacterial and protozoan activities to degrade organic compounds

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Treatment Stages

 Tertiary: Advanced stages of treatment to raise

the effluent quality to the standard required before it is discharged to the receiving environment

Potential steps: Filtration, polishing, ponding (lagoons, wetlands), nutrient removal,

disinfection.

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Common Options for Secondary

Sewage Treatment

Treatment Process

Description Key Features

Activated Sludge Process

(ASP)

Oxygen is mechanically supplied to bacteria which feed on organic material and provide treatment

Sophisticated process – many

mechanical & electrical parts, needs careful control of operator; provides high degree of treatment.

Aerated lagoons

Like lagoons but with mechanical aeration

Not very common; oxygen

requirement mostly from aeration and hence more complicated and higher operational and maintenance costs.

Land

Treatment

(soil –aquifer treatment – SAT)

Sewage is supplied in

controlled conditions to the soil

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