WATER TREATMENT METHODSWATER TREATMENT METHODS

1 G l1. General- Contaminants in water and wastewater removed

by meansby , , means- Specific removal methods classified as:

i) unit operationsi) unit operationsii) unit operationsiii) unit operationsiii) unit operations

- Processes occur in variety of combinations, depend on specific needs

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p p

WATER TREATMENT METHODSWATER TREATMENT METHODS

1 1 Ph i l U it O ti ( )1.1 Physical Unit Operations (processes)

- Application of physical force- Typical processes include:

i) screeningii)

iii)iii)

iv)

v)

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v)

WATER TREATMENT METHODSWATER TREATMENT METHODS

1 2 Chemical Unit Operations1.2 Chemical Unit Operations- Treatment brought about by chemical addition or

chemical reaction- Typical processes include:

i) chemical precipitationii) adsorptioniii)

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WATER TREATMENT METHODSWATER TREATMENT METHODS

1 3 Biological Unit Operations1.3 Biological Unit Operations- Removal of contaminants by biological means

Primarily removal of biodegradable substances- Primarily removal of biodegradable substances- converted into , .

- Typical processes include:Typical processes include:i) biological filtrationii) treatmentiii) anaerobic digestion

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WATER TREATMENT METHODSWATER TREATMENT METHODS

P f W t T t tDrinking

Purpose of Water Treatment

“Provide potable water that is chemically and i bi l i ll f f h ti ”microbiologically safe for human consumption”

2.1 Pretreatmenti) Screening (surface waters)ii) Pre-sedimentation (lake waters)

t d d lid- to remove suspended solids- may require chemical addition to assist

(polyelectrolytes alum)

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(polyelectrolytes, alum)

WATER TREATMENT METHODSWATER TREATMENT METHODS

iii) Chemical treatmentiii) Chemical treatmente.g. chlorine- potassium permanganate- chlorine dioxide- ozone

iv) Aeration- oxidizes ferrous and manganous ions to

insoluble species- removes gases such as

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WATER TREATMENT METHODSWATER TREATMENT METHODS

2 2 Coagulation/Flocculation/Sedimentation2.2 Coagulation/Flocculation/Sedimentation- Used for removal of turbidity and pathogenic

organisms

- Chemical coagulation and flocculation producesChemical coagulation and flocculation produces “flocculant” precipitate that makes particles come together and settle more readilyPrecipitate removed by sedimentation- Precipitate removed by sedimentation

- Typical chemical coagulants include- aluminum sulfate

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- ferric chloride- lime

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WATER TREATMENT METHODSWATER TREATMENT METHODS

2 3 Filtration2.3 Filtration- Used to remove any remaining solids following

sedimentation- Often use sand or mixed media filters- Activated carbon placed on top of filter beds

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SingleMedia

DualM diMedia Media

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WATER TREATMENT METHODSWATER TREATMENT METHODS

2 4 Di i f ti2.4 Disinfection- Add disinfectant prior to distribution system

Ensure control of pathogenic organisms- Ensure control of pathogenic organisms

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12

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WATER TREATMENT METHODSWATER TREATMENT METHODS

2 5 Sludge Processing2.5 Sludge Processing- Sludge composed of chemical residues

Hi t i ll di h d ith t i- Historically discharged without processing

- Now, sludge handling required

P i f l d- Primary sources of sludge

i) Chemical coagulation, precipitation, softening –d i di t ti t kremoved in sedimentation tanks

ii) Filter backwash

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WATER TREATMENT METHODSWATER TREATMENT METHODS

Disposal via:- Disposal via:i) Discharge to municipal sewerii) Drying lagoonsii) Drying lagoonsiii) Drying bedsiv) Centrifugationiv) Centrifugationv) Pressure filtrationvi) Chemical recoveryvi) Chemical recovery

- Ultimately to landfill

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Ultimately to landfill

WATER TREATMENT METHODSWATER TREATMENT METHODSWater Source Considerations

Sources - groundwater- river water- lake water or impounding reservoirs

- Water quality in rivers dependent upon input to watershede g municipalitiese.g. - municipalities

- industries- agricultural processes

- Important to practice watershed management- limit access

limit discharges

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- limit discharges- pretreat water in some cases (algae blooms)

WATER TREATMENT METHODSWATER TREATMENT METHODS

- Water quality in rivers and lakes influenced by:- Climatic conditionsSeasonal changes- Seasonal changes

Examples - “ ”p- caused by change in temperature- characterized by high flows, high turbidity, taste and odour problemstaste and odour problems

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WASTEWATER TREATMENT OVERVIEW

1 Wastewater Types:1. Wastewater Types:

i) sanitary ii) i d t i lii) industrialiii) stormwateriv) infiltration/inflowiv) infiltration/inflow

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WASTEWATER TREATMENT OVERVIEW

2 P f W t t T t t2. Purpose of Wastewater Treatment

- Primary concern (municipal wastewater)- reduction of concentration and

- Industrial wastewater h t i ti i d t t t i d t- characteristics, required treatment - industry

specific

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WASTEWATER TREATMENT OVERVIEW

3 T t t M th d3. Treatment Methods

4 main stages - Pretreatment- Primary - Secondary

Tertiary- Tertiary

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WASTEWATER TREATMENT OVERVIEW3. Treatment Methods

3.1 Pretreatment3.1 Pretreatment- defined as "removal of w.w. constituents that may

cause maintenance or operational problems" (M&E)

i) Screening (bar screens) ii) Comminution

iii) Grit Removal

iv) Flow Measurement

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v) Pumping

WASTEWATER TREATMENT OVERVIEW3. Treatment Methods

3 2 P i T t t (S di t ti )3.2 Primary Treatment (Sedimentation)

- Removes suspended matter by reducing watervelocityvelocity

- Removes 30-50% of suspended solids- Removes a portion of organic matterRemoves a portion of organic matter

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WASTEWATER TREATMENT OVERVIEW3. Treatment Methods

3 3 S d T t t (Bi l i l St bili ti )3.3 Secondary Treatment (Biological Stabilization)

- Removes biodegradable organics and suspendedmatter not removed by 1º treatmentmatter not removed by 1º treatment

- Conventional 2º treatment processes include:- activated sludge- fixed film reactors (RBCs)

lagoons- lagoons

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WASTEWATER TREATMENT OVERVIEW3. Treatment Methods

3 4 T ti T t t3.4 Tertiary Treatment

- Typically used for nutrient (P, N) removal to reduceeutrophication in receiving waters

- Typical 3º treatment processes include:yp p- chemical addition (alum)- special biological processes- disinfection

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WASTEWATER TREATMENT OVERVIEW3. Treatment Methods

3 5 Sludge Processing3.5 Sludge Processing

- 1º and 2º processes concentrate waste organics intosmall volumes a o u e

- Construction of sludge processing facilities approx.1/3 of treatment plant cost

- Common methods for raw sludge ‘disposal’ include:- anaerobic digestion

h i l d t i- mechanical dewatering- centrifugation- landfill l d li ti

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landfill- incineration

- land application

WASTEWATER TREATMENT OVERVIEW3. Treatment Methods

“Water Supply and Pollution Control” 6th Edition 1998 Viessman & Hammer pp 334

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Water Supply and Pollution Control 6th Edition, 1998, Viessman & Hammer , pp 334

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