Building Services Topic: Water Treatment Presentation Created By: Padraig McMahon Student ID:...

Building Services

Topic: Water Treatment Presentation

Created By: Padraig McMahonStudent ID: 0236381

Water Treatment Mr McMahon

Mr. McMahonWater Treatment

Hydrological Cycle

Water Conists in three forms Solid, Liquid, and vapour Circulates through the biosphere

Step 1 (Evapouration)Water Leaves the earths surface and enters the atmosphereBy evaporation.(Transpiration of plants)

Step 2 (Condensation)Vapour forms clouds. As the air pressure & temp change, the

vapour condenses depositing moisture.


Hydrological Cycle


Hydrological Cycle

Step 3 (Precpipatation) Rainfall occurs when the droplets formed in condensation are large enough

Dew Point The temp at which air cannot hold all the

moisture in it and dew begins to form

Step 4 (Infiltration)Rainwater Flows through rivers/ streams back to seaSoaks into soil (groundwater) and eventually runs back to ocean


Hydrological Cycle


Hydrological Cycle

Process Provides Water that is constantly cycled & Recycled Cleaned and repurified Maintains good stream quality


Pure Water

Solids In Water Great ConcernProvides adsorption sites for

biological and chemical agents

Solids Consists of Inorganic, organic or

immisible liquids like oils,grease,etc..

Inorganic particles could be clay,silt,soil,etc..

Organic particles could be plant fibers, bacteria, etc..


Turbidity The passage of light through water, high turbidity can result from,

• Very small particulate Colloidal material e.g rocks, silt, etc..

Pure Water

Colour Pure Water has no colour, Foreign substances like Vegetation, minerals, wastes can often tint water. Waters colour can affect

• Marketability• Safety issues• Laundering• Food Processing• Papermaking, etc..


Temperature Temp of the water within

the treatment plant can affect the strength at which the chemicals work at.

Pure Water

Drinking Standards All these qualities are

needed to create safe drinkable water.

Regulations are needed and here is one chart of regulations from America


Surface Water

4,250 billion gallons of water per day falls on US mainland 66% returns to the atmosphere by evaporation.

Sources may include Rivers, streams Lakes Impoundments (man made dam) Springs Rain catchments Tundra ponds- or peat bogs


Surface Water

Surface Water Advantages: Easy to locate Not tainted with minerals (leached

out during contact with earths surf

Surface Water Disadvantages

Human interference (can affect run off rate as well)

Easily contaminated with micro organisms


Groundwater

Water that has fallen below the earths crust and not evaporated is known as ground water. It travels through the earths crust

reaches aquifers and passes on to what is known as a water table

• Aquifers are simply dissolved rocks that allow water to pass through them deep underground.


Groundwater

Advantages The water is not as easily contaminated. (Natural filtering process) Quality and quantity remains constant throughout the year Less affected by short-term droughts

Disadvantages Higher operational costs, (Groundwater has to be pumped) If contaminated very hard to disinfect Due to long contact with earth, minerals are present, Which leads to hardness in operational materials, e.g. pipes.


Water Treatment Process

Steps that water either Ground or Surfacewater passes through in order to be correctly treated


Water Intake Water has to be taken from source

to treatment Facility

Water Quality Best at surface Various Entry points Top Ports are only opened

Advantages Option of ports in seasonal change Control of quantity, quality of water


Water Intake

There are various method of water intake, submerged ports, shoreline structures, etc..


Water Intake

Screening

Ports


Screening The removal of debris (most important for surface water)

Various types

Trash screens or rakes Travelling screens Drum screens Bar screens Etc…


Screening

Step 1Largest Debris is taken by trash screens or rakes they are made from steel

High Density Polymers are becoming used more often

Spacings of 1.5inches to 4inches (37mm-100mm)

Mountained on a fixed structure


Screening Traveling Water Screens

Series of wire mesh panels,Bolted to frames and attached to aligned roller chains

Placed in Channel of flowing Water Removes floating debris High Pressure sprays remove

debris at top of screens


Very few moving parts Simplicity of design &

construction means low Instillation Costs Operational costs Maintenance Costs

Screening

Drum Screens

Screen is mountained on a horizontal axis, it turns slowly picking up debris flowing through it


More Common at wastewater facilities

Handles large debris Debris is removed by

wiper mechanism

Screening

Bar Screens


Coagulation Process PurposeScreened water is pumped into tanks and allowed settle.Gravity and sedimentation allows particles that are denser than

water sink.

Not all particles are removed, colloids, bacteria, turbidity, etc.. remains

Cogulation process provides help. Rapidly mixing chemicals Slowly stirring mixture Finally sedimentaion removes the particles


Cogulation Rapidly mixes certain chemicals into the water to allow particles to clump togeather easlier

Coagulation

Types of chemicals mixed are dependent on individual plant or process schemes.

The most common

added is Aluminium

Fact “Colloidal particales must be coagulated to be removed”!!


The clumping of particles as a result of cogulation, It is the most critical factor that affects particle removal.

Flocculation

Slow mixing process (designed to bring particles into contact)

Collide, stick, agglomerate (grow), & settles

Warnings Too much mixing (breaks floc down into smaller units Speed of mixing water (strictly controlled Gentle agitation for about 30mins using redwood paddles

is standard


Flocculation Warnings

Too much mixing (breaks floc down into smaller units

Speed of mixing water (stricly controlled

Gentle agitaion for about 30mins using redwood paddles is standard

Big Red-Wood Panels

Coagulation TankFlocculation Tank


Summary

Coagulation and Flocculation work together to remove much of the hidden debris within the water

The smaller impurities that remain uses more complex processes to ratify the water

Flocculation


Sedimentation Sedimentation (or Clarification) is a

physical process that seperates solids from influent water by gravitional action

Process Water flows horizontally

through sedimentation basins. Detention time 1-10hrs

(typically) Water rises floc settles, to

bottom Expelled mechanically by

sludge removal machinery


Floc Particals still remain, Lighter Particles flow out Sludge disposed of in

lagoon.

Sedimentation

Sedimentation balances time efficiency against removal rate efficiency

Physical laws of gravity are evident for the removal of particales too small for intial screening to halt


Filtration Filtration is also a physical process. Last physical step in process

Generally 5% of suspended impurities remain after sedimentation Filtration is a polishing process, and it involves passing

water through a porous granular material

Various Types Rapid sand, slow sand, diatomaceous earth, package systems


Slow Sand Filters Bacteriological action

Filtration

Sand develops a film of fine particales.

Gradual loss of flow

Fine pore spaces clog easily Maual scraping of top 20mm’s of

sand is required every fortnight


Anthracite Coal Filters Consists of coal and fine sand Coal traps large floc Fine sand traps smaller

impurities

Filtration

The Process is called in-depth filtration, as the impurities are not simply screened our or removed at the surface of the filter bed, as the case inslow sand filters


Chlorination

In USA the disinfectant choice has been chlorine Effective, Relatively inexpensive, Meets Regulation Standards

In USA the disinfectant choice has been chlorine Effective, Relatively inexpensive, Meets Regulation Standards


All Vacuum Chlorinator

Chlorination

Vacuum Formed by water flowing through ejector unit at high velocity

Chlorine is sucked out along with the water

“Venturi” Tightning of a tube to create higher pressure & velocity at the point e.g carburettor


Other Modern methods include: Uv radiation Ozonation Electrodialsis Reverse Osmosis

Chlorination

This ultraviolet (UV) radiation and oxidation technology uses UV radiation, ozone, and hydrogen peroxide to destroy toxic organic compounds

Building Services Topic: Water Treatment Presentation Created By: Padraig McMahon Student ID:...

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