Water Treatment

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WATER TREATMENT by: Ma. Teresa P. Francisco DT Student

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Water treatment is the process of making water suitable or acceptable for an end-use.

It removes existing water contaminants and so reduces their concentration that the water becomes fit for its desired application.

Why Water Treatment? Natural waters are rarely of satisfactory

quality for human consumption or industrial use and nearly always needed to be treated.

INTRODUCTION

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In the United States and the United Kingdom, by far the most common sources of raw freshwater are rivers and lakes, though in recent decades, more sources of groundwater are being utilized.

Some groundwater sources are so pure that no treatment is necessary although when used for public supplies, local water authorities tend to apply a disinfection process, but this is primarily for disinfection purposes of the distribution network.

INTRODUCTION

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The objectives of water treatment are to produce:

Water that is safe for human consumption

Water that is appealing aesthetically to the consumer

Water at a reasonable cost

INTRODUCTION

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Advanced water treatment processes are often required by industry, e.g. the beverage or pharmaceutical industries. Such industries may have higher standards than those for potable supplies.

INTRODUCTION

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Public water supplies normally service the requirements of:

Domestic householdsFire fightingIndustrialCommercial

AMOUNT OF WATER REQUIRED

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Source: UN Development Program 2006

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Development of New Water Sources: Angat Dam - the only present source of

water supply for the MWSS service area serving a total of 13 million population out of the total service population of 15 million, or only 87% total service coverage.

Angat Dam provides a supply volume of 4,000 million liters per day (4,000 mld) out of the present demand of 4,395 mld, or a deficit of 395 mld.

By 2015, the projected demand is expected to reach 5,054 mld, thus requiring the development of supplementary sources of water to address the increasing demand.


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In discussing water quality, two sets of standards exist:

The quality of raw water The quality of the treated potable water

WATER QUALITY STANDARDS

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Organoleptic Parameters Physicochemical

Parameters Parameters Concerning

Substances Undesirable in Excessive Amounts

Parameters Concerning Toxic Substances

Microbiological Parameters

WATER QUALITY PARAMETERS

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Organoleptic parameters■ Turbidity ■ Colour ■ Odour ■ Taste


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TurbidityTurbidity refers to how

clear the water isThe greater the amount of

total suspended solids in the water, the murkier it appears and the higher the measured turbidity


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Materials that cause water to be turbid include

ClaySiltPlanktonMicroscopic organismsSoluble colored organic

compound


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COLOUR Colour is an optical parameter consisting in absorbing of a part of spectrum of visible radiation by substances dissolved in water, and suspension particles present in water or sewage.


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Colour in water may appear as the result of different sources activity:type of vegetationdecay of plant matteralgae growthplanktonminerals (iron, manganese and copper)


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TASTE AND ODOURare usually inter-related. Compounds in water that are perceived as giving it a taste are generally inorganic substances present in concentrations such higher than those of organic pollutants


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TASTE AND ODOURInorganic chemicals that can affect taste but not cause any odour are salt, minerals, metals.

A few inorganic chemicals can cause both taste and odour problems. These are ammonia, chlorine, hydrogen sulphide.


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TASTE AND ODOUROrganic chemicals usually affect both taste and odour: the compounds concerned include hydrophilic acids, carboxylic acids, amino acids, carbohydrates, hydrocarbons, biological decay products, petroleum products and pesticides.


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Physico-chemical parameters

Temperature and pH Conductivity (salinity)ChloridesSulphatesSilicaCalcium


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Physico-chemical parameters

MagnesiumSodiumPotassiumAluminumTotal hardnessDry residuesCO2


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Parameters Concerning Substances Undesirable in Excessive Amount

Inorganic Compounds: nitrates, nitrites, ammonium, phosphorus, fluoride, metals (Iron, Manganese, Copper)

Organic conontaminants: THM’s, phenols, surfactants


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Parameters Concerning Toxic Substances

ArsenicCadmiumCyanideChromium LeadMercuryNickel Etc


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Microbiological ParametersBacteria Viruses


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Water for treatment and subsequent public consumption is normally sourced from:

Rivers: upland and lowlandLakes and reservoirsGroundwater aquifers

The selection of the source is governed by many factors, including proximity to the consumers, economics, long-term adequacy of supply and raw water quality.

WATER SOURCES AND THEIR QUALITY

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Each source presents its own problems Surface water has elevated levels of soil

particles and algae, making the water turbid may contain pathogens

Groundwater has higher levels of dissolved organic matter (yellow color) and minerals such as iron

Both sources may have high levels of calcium and magnesium (hardness)

both can be contaminated by toxic chemicals

WATER SOURCES AND THEIR QUALITY

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Four classes of water treatment:

WATER TREATMENT PROCESSES

Class Description Source

A No treatment Some borehole water

B Disinfection only Occasional upland water, some borehole water

C Standard water treatment Lowland rivers and reservoirs

D Special Water Treatment Some rural supplies (Fe and Mn)Color removalIndustrial waterAlgae removalOrganics removal

CONVENTIONAL WATER TREATMENT

Screening

Coagulation

Flocculation

Sedimentation

Filtration

Disinfection

Storage

Distribution

Raw water

AlumPolymers Cl2

sludge

sludge

sludge

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SCREENING

Removes large solidslogsbranchesragsfish

Simple processmay incorporate a mechanized trash removal system

Protects pumps and pipes in Water Treatment Plants

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COAGULATION Small particles are

not removed efficiently because they settle too slowly

they may also pass through filters

easier to remove if they are clumped together

Coagulated to form larger particles, but they don't because they have a negative charge

repel each other (like two north poles of a magnet)

In coagulation we add a chemical

such as alum which produces positive charges to neutralize the negative charges on the particles

particles can stick together

forming larger particles

more easily removed process involves

addition of chemical (e.g. alum)

rapid mixing to dissolve the chemical

distribute it evenly throughout water

Coagulants

Aluminum Sulfate Al2(SO4)3

Ferrous Sulfate FeSO4 Ferric Sulfate

Fe2(SO4)3 Ferric Chloride FeCl3 Lime Ca(OH)2

Aluminum salts are cheaper but iron salts are more effective over wider pH range

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FLOCCULATION Now the particles have

a neutral charge They can an stick

together The water flows into a

tank with paddles that provide slow mixing

bring the small particles together to form larger particles called flocs

Mixing is done quite slowly and gently in the flocculation step

If the mixing is too fast, the flocs will break apart into small particles that are difficult to remove by sedimentation or filtration.

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SEDIMENTATION

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Water flows to a tank called a sedimentation basin

Gravity causes the flocs to settle to the bottom

Large particles settle more rapidly than small particles

It would take a very long time for all particles to settle out and that would mean we would need a very large sedimentation basin.

So the clarified water, with most of the particles removed, moves on to the filtration step where the finer particles are removed

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FILTRATION The filtration apparatus is a concrete box

which contains sand (which does the filtering), gravel (which keeps the sand from getting out) and underdrain (where the filtered water exits)

After the filter is operated for a while, the sand becomes clogged with particles and must be backwashed

Flow through the filter is reversed and the sand and particles are suspended

The particles are lighter than the sand, so they rise up and are flushed from the system. When backwashing is complete, the sand settles down onto the gravel, flow is reversed and the process begins again

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DISINFECTION With particles removed, it only remains to provide disinfection, so that no pathogens remain in the water

Protozoan pathogens are large in size and have been removed with other particles

Bacteria and viruses are now destroyed by addition of a disinfectant

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DISINFECTION

ChlorinationEnough chlorine is added so that some remains to go out in the water distribution system, protecting the public once the water leaves the plant

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Pumping of the clean water produced at the treatment plant to the community is called distribution

This can be done directly or by first pumping the water to reservoirs or water storage tanks

DISTRIBUTION

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Water fluoridation is the controlled addition of fluoride to a public water supply to reduce tooth decay. Fluoridated water has fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride.

FLOURIDATION

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Ground waters are more likely to have a higher fluoride content.

Most surface water have negligible amount.

FLOURIDATION

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FLOURIDATION

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Purposes:To take a water treated by standard processes and to improve it to exceptionally high quality as often required by particular industries.

To treat a water containing specific chemical or microbiological contaminants to an acceptable standard, i.e removal of iron and manganese, the removal of blue-green algae, the removal of specific organics

ADVANCED WATER TREATMENT PROCESSES

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ADVANCED WATER TREATMENT FACILITIES

Silicon ValleyAdvance Water Purification Center

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ADVANCED WATER TREATMENT FACILITIES

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Techniques Used:Iron and manganese removal - iron is removed by pressure filters while manganese is removed by gravity sand filters

Ion Exchange and inorganic absorption - water softening by exchanging undesirable calcium and magnesium cations with sodium. Also used to remove undesirable cations including barium, strontium and radium and undesirable anions including fluoride, nitrates, silicates and chromates

ADVANCED WATER TREATMENT

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Techniques Used:Adsorption of organics – undesirable contaminants are adsorbed on to solid adsorbents.

Membrane processes – uses microfiltration, ultrafiltration, reverse osmosis, electrodialysis

Oxidation including chemical oxidation – two or more chemical species are added with the purpose of increasing the oxidation state of one.

ADVANCED WATER TREATMENT

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Manila Water Lakbayan Water Trail

The Angat River is the largest and most important source of water for our region.

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Metro Manila Water Supply System

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Thank you!!

Water Treatment

Environment

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