water contaminants and their health impacts

8/10/2019 Water Contaminants and Their Health Impacts

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Water Contaminants &

Their Health Impacts

ByMuhammad Saqib NawazPhD Scholar IESEResearch Associate IESETVF NICE


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Why contaminants dissolved inwater?The hydrogen bonding in water is responsible for its

universal solvent character.The inorganic are dissolved due to neutralization ofions and organics due to bonding with polar oxygenand hydrogen of water.100% pure water is not found in nature, even watervapors condensing in air contains solids, dissolvedsalts and gases.

Even when the condensed water (rain water) falls itsweeps many materials from air, and becomes morecontaminated on reaching ground, running onsurface and percolating through soil.

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The materials found in water may be divided intoliving organisms and solids.Remember all of them are not harmful and someare desirable for health like minerals.

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Inorganic ContaminantsInorganic contaminants include both suspendedand dissolved materials.Suspended material is undesirable due to tworeasons, one is aesthetic and other is its shielding

effect for microorganisms against disinfection.Dissolved inorganics having health impactsincludes aluminium, arsenic, barium, cadmium leadetc.

Pak EPA has established a maximum contaminantlevel (MCL) for all those metals.

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Arsenic issue, Lahore and Multan in Pakistan withhighest As concentration, Skin diseases and fatal

in high doses.Ba, Cd, Cr are acute toxic , Cr issue from Qasur tannery wastewater.

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Pak EPA Standards

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Organic ContaminantsBoth naturally occurring and artificial organics arefound in water.The natural organics produce color, taste and odor.Man made organics are carcinogenic. Sometimesby chemical treatment the organic materialchanges its form from one to other, which is moretoxic.

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Watershed & ReservoirprotectionTo ensure the uncontaminated water supply thewatershed area must be protected.If the reservoir is intended to do only disinfection thenthat reservoir must be prohibited from anyrecreational use or any other purpose.

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Swimming (contaminating ) and water sportsrestricted to the distance of 2km at least from water

intake.Non contact (non contaminating) recreation such asfishing, boating restricted to 200 m from intake.Ground water and well protection:

These supplies and wells can get contaminated withsurface water during floods and by percolation ofwaste material from soil.Wells protected by careful construction techniques

which require casing be grouted down to the firstimpermeable stratum.Casing extend above surface of ground and concreteapron protect the area surrounding the casing.

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Protection within treatment anddistribution systemCareful design of treatment system.

Avoid common wall constructionbetween treated and untreated waterbasins.

An emergency power and chemicalsupply.

Avoid sewer and water lines in closeproximity.

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Diseases Types:

1. Water borne diseases2. Water washed diseases

3. Water based diseases4. Insect Vector diseases

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Water Borne Diseases

These diseases occur due to thedrinking of the contaminated water.

For Example:Cholera

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Water Washed Diseases

These are caused by washing the body withcontaminated water .

For Example

Scabies

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Water Based Diseases

Diseases caused by parasites found in

intermediate organisms living in

contaminated water.

For Example

Guinea worm disease

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Insect Vector Diseases

These diseases are transmitted through

insects which grow in presence of water.

Malaria vector -borne disease, responsible for

more cases of morbidity and mortality than any

other tropical disease

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Water Treatment

ByMuhammad Saqib NawazPhD Scholar IESEResearch Associate IESETVF NICE


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Water Treatment

Water treatment transforms raw surface andgroundwater into safe drinking water.

Water treatment involves two major processes:

physical removal of solids and chemicaldisinfection.


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Unit Operations/ProcessesDesigned to Remove Solids

ScreeningSedimentationCoagulation/flocculationFiltration slow sand filters rapid sand filters diatomaceous earth filters membrane filters

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Conventional Surface WaterTreatment

Screening

Coagulation

Flocculation

Sedimentation

Filtration

Disinfection

Storage

Distribution

Raw water

AlumPolymers Cl2

sludge

sludge

sludge

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Screening

Removes large solids branches rags fishSimple process may incorporate a mechanized trash

removal system

Protects pumps and pipes in WTP

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Sedimentationthe oldest form of water treatmentuses gravity to separate particles fromwater often follows coagulation and flocculation.

Because of the high volumetric flow ratesassociated with water treatment systems,gravity sedimentation is the only practical,economical method to remove these solids.

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Gravity separation can obviously be applied

only to those particles which have densitygreater than water. But this density must besignificantly greater than that of water due toparticle surface effects and turbulence in thesedimentation tanks.


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Sedimentation: Effect of thesolution concentration

Dilute suspensions Particles act independently

Concentrated suspensions Particle-particle interactions are

significant Particles may collide and stick

together (form flocs) Particle flocs may settle more quickly Particle-particle forces may prevent

further consolidation

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Sedimentation in dilutesuspensions?What are the importantparameters? Initial conditions (size,

shape) After falling for some time

(hindrance)...

What are the importantforces? Gravity Drag Force

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1. Discrete Sedimentation

Occurs in dilute suspensions, particleswhich have very little interaction with eachother as they settle.

Particles settle according to Stokes law

Design parameter is surface overflow rate

(Q/A s)

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2. Flocculent Sedimentation

Particles flocculate as they settle Floc particle velocity increase with time Design parameters:

1. Surface overflow rate2. Depth of tank

or,3. Hydraulic retention time

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Comparison of Type I and IIsedimentation


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3. Zone or Hindered Settling

In more concentrated suspensions like mixedliquor, a matrix of interlinked particles is formed, allsettling with the same rate: the zone settlingvelocity. This type of settling is not dictated by theforces acting on each particle alone, but rather bythe forces acting on the whole interlinked sludgemass.For zone settling to apply, the minimum sludgeconcentration is in the range of 0.5 to 1.0 g/l.

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4. Compressional Settling

Sedimentation of suspension with solidsconcentration so high that the particles arein contact with one another and furthersedimentation can occur only bycompression of the mass. The lower portionof a sludge thickener is an example ofcompression settling.

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There is hope if people willbegin to awaken that spiritualpart of themselves, that we arecaretakers of this planet.

Thanks...

water contaminants and their health impacts

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