Water Quality, pollution and treatment units.ppt

8/10/2019 Water Quality, pollution and treatment units.ppt

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Water Quality, Pollution,

and Treatment Plants


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Objectives

Introduce water quality standards

Introduce typical treatment processes and

design flow rates

Present examples of flow sheet diagrams


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Water Usage

Domestic

Industrial

Agriculture

Fish farming

Recreational


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Pathogens

Pollution

Physical

Chemical

Biological

RadiologicalThermal

Solids

Oxygen demanding waste

Nutrients

Heavy metals

Pesticides

Volatile organic compounds

Hardness

Radio-isotopes


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Storm water pollution

Scale formation due to

water hardness

Red tide due to algae contamination


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Stream

Sea

Harbor Lake

Water Quality

Standards

A.

Standards forwater usage

B.

Discharge or

effluentstandard

C.

Water qualityobjective limit

Drinking

Irrigation

Recreational

Industrial

Stream

Sea

Harbor Lake


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A. Drinking Water Standard

Inorganic ChemicalsArsenic 0.05 Mercury 0.002

Barium 2 Nickel 0.1

Cadmium 0.005 Nitrate (as N) 10

Chromium (total) 0.1 Nitrite (as N) 1

Copper TT Nitrate + nitrite 10

Fluoride 4 Selenium 0.05

Lead TT Thallium 0.002

Asbestos 7106fiber /L

VOCs

Benzene 0.005 Ethylbenzene 0.7

Carbon tetrachloride 0.005 Vinyl chloride 0.002

A1. US Primary Drinking WaterMCL in mg/L (partial list)


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Concentration, mg/L

Guideline U.S. standards

Constituent WHOb Canadac MCLG MCL

Antimony 0.005 0.006 0.006Arsenic 0.01 0.025d 0 0.05Asbestos 7 X 106e 7 X 106eBarium 0.7 1.0 2 2Beryllium 0.004 0.004

Boron 0.3 5 d

Cadmium 0.003 0.005 0.005 0.005

Chromium 0.05 0.05 0.1 0.1

Cyanide (as CN) 0.07 0.02 0.2' 0.2'Fluoride 1.5 1.5 4

0

4TTgLead 0.01 0.01

Mercury, total 0.001 0.001 0.002 0.002

Molybdenum 0.07

Nickel 0.02 0.1 0.1

Nitrate (as N) 11.3 10 10 10Nitrite (as N) 0.91 1 1

Selenium 0.01 0.01 0.0 0.05Thallium 0.0005 0.002

'See notes at beginning of Section 8.6.

'Reproduced by permission from WHO (1993), Guidelinesfor Drinking Water Quality, vol. 1- Recommenda-

tions, 2nd ed., World Health Organization, Geneva.

'MAC.d Interim value (IMAC).

'Based on fibers >10 Am.

'Proposed.

gTreatment technology specified.

Different countries may have different drinking water standards


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A2. Bacteriological limits for drinking water

US EPA states that bacterial quality criteria for

drinking water from public supplies require not morethan 1 total-coliform/100 ml as the arithmetic meanof all

water samples examined per month, with no more than 4

coliforms/100 mlin any sample if the number of samples

is 20/month, or no more than 4 per 100 ml in 5% of thesamplesif the number of samples exceeds 20per month.

Bouwer, Groundwater Hydrology, McGraw-Hill, 1978.


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Minimum no. of Minimum no. of

routine samples routine samplesPopulation served per month Population served per month

25-1000 1

2

3

4

5

67

8

9

59 001-70 000 701001-2500 70 001-83 000 802501-3300 83 001-96 000 903301-4100 96 001-130 000 1004101-4900 130 001-220 000 120

4901-5800 220 001-320 000 1505801-6700 320 001-450 000 1806701-7700 450 001-600 000 2107701-8500 600 001-780 000 240

8501-12900 10 780 001-970 000 27012 901-17 200 15 970 001-1 230 000 300

17 201-21 500 20 1 230 001-1 520 000 330

21 501-25 000 25 1 520 001-1 850 000 36025 001-33 000 30 1 850 001-2 270 000 390

33 001-41 000 40 2 270 001-3 020 000 420

41 001-50 000 50 3 020 001-3 960 000 450

50 001-59 000 60 3 960 001 or more 480

Number of samples taken for coliform testing depends on the

population served by the treatment facility


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Example

Water samples from the effluent of a water treatment plant of a town

(39,000 people) were analyzed at regular intervals over a month period.

The numbers of coliform/100 ml sample were as shown below:

CountNo.CountNo.CountNo.CountNo.

03102111101

03202201202

23322321313

03442451404

03562521515

03612611626

03702711707

53802801808

03902901919

140030020010

According to EPA

regulations, are the

number of samples

and effluent bacterial

quality acceptable?Explain.


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Solution

No more than 5% of the samples should have more than 4 coliform/100ml.

Since the number of samples is 40 then no more than 2 samples (5%)

should have more than 4 coliform/100ml. However, there are three

samples (sample # 14, 25, and 38) that have more than 4 coliform/100ml.

So this is a violation of the regulations.

The population is 39,000, so the minimum number of samples should be

40. Since we have 40 samples then the number of samples taken is OK

The arithmetic average of coliform should not be more

than 1. Since the average number of coliform is 0.95

which is less than 1 then this condition is OK


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A3. Secondary Standard for Drinking Water

Contaminant Level Effects

Al 0.05-0.2 mg/L Water discoloration

Cl 250 mg/L Taste, pipe corrosion

Color 15 color units Aesthetic

Cu 1 mg/L Taste, porcelain staining

F 2 mg/L Dental fluorosis

Foaming agents 0.5 mg/L Aesthetic

Fe 0.3 mg/L Taste, laundry staining

pH 6.5-8.5 Corrosive

Sulfate 250 mg/L Taste, laxative effects


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B. Effluent Standards

30 consecutive

days

7 consecutive

days

30 mg/l45 mg/lBOD

30 mg/l45 mg/lSS

10 mg/l20 mg/lOil and grease

pH: 6-9

BOD and SS removal > 85%

B1. US National Pollutant Discharge Elimination System

(NPDES)


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B2. Discharge standard of wastewater into Jebel Ali Harbor

Maximum limitUnitParameter

50mg/lTotal Suspended solids

6-9-pH< 35oCTemperature

50mg/lBOD

>3mg/lDissolved Oxygen

40mg/lNitrate

0.05mg/lArsenic

0.05mg/lCadmium

0.5mg/lCopper

0.1mg/lLead

0.001mg/lMercury10mg/lOil & Grease

0.1mg/lPhenols

75mg/lTotal Organic Carbon

1000Cells/100mlTotal Coliform


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C. Water Quality Objective Limits

Standard (mg/l or as noted)Indicator

0.05Lead

1Oil and grease

0.2Aluminum

0.01Arsenic

0.003Cadmium

Not less than 5 mg/l or 90% saturationDissolved oxygen

0.001Mercury

10BOD5

0.5Nitrate-N

0.001Aromatic hydrocarbons

1 pH unit from background level or 6.5-8.5pH

10 (mean), 25 (maximum)Suspended solids

2oC from background levelTemperature

2% from background levelTotal dissolved solids

Jebel Ali Harbor water quality objective limits


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Parameter/Problem Treatment Process

Large debris (particles) Screens (Physical)Settlable solids Grit chamber (Physical)

Suspended solids Coagulation (Chemical)/flocculation

(Physical)/Sedimentation (Physical)

Filtration (Physical)BOD Biological reactors (Biological)

Heavy metals Depending on the metal: Sorption (Chemical),

ion exchange (Chemical), or precipitation

(Chemical)

Trace organic

contaminants

Activated carbon (Chemical) or air stripping

(Chemical) if chemicals are volatile in nature

Microorganisms Disinfection (mainly Chemical)

Typical Treatment of Contaminants


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Water Treatment Plant (WTP)

A WTP consists of processes to remove contaminants present in the water

such that produced water is suitable for drinking.

Raw water

influent

Produced water

Effluent

WTP

A flow sheet for the plant shows the sequence of the processes used:

The design of a WTP depends on (1) the quality of raw water, (2) the quality

of produced water and the (3) capacity of the plant.

The capacity of the plant depends on the design period (15-25 yrs), thepopulation served, and the per capita water consumption.


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Wastewater Treatment Plant (WWTP)

A WWTP consists of processes to remove contaminants present in the

wastewater such that produced water is suitable for discharge or reuse.

Wastewater

Or influent

Treated

wastewater or

EffluentWWTP

A flow sheet for the plant shows the sequence of the processes used:

The design of a WWTP depends on (1) the characteristics of wastewater, (2)

the desired characteristics of treated wastewater and the (3) capacity of the

plant.

The capacity of the plant depends on the design period (15-25 yrs), the

population served, and the per capita wastewater generation.


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Design flow rate =per capita water consumption*population at the end

of design period.

Note that the per capita water consumption increases about 10% of the

percentage increase in population.

The percent increase in population = (150000-100000)/100000= 50%

Per capita consumption at the end of design

period=500(100%+50%*10%)=525 L/d

Design flow rate = 150,000 * 525 L/d= 78750 m3/d

Example

A small town with a population of 100,000 and a per capita water

consumption of 500 L/d. A water treatment plant is to be built to serve this

town for the coming 10 yrs. Estimate the design flow rate assuming the

population after 10 yrs is 150,000.

Solution

Flow Rates: Water Treatment Plants


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Minimum flow rate:Important for design of pipes and channels that carry wastewater with

suspended solids. Minimum velocity to keep organic solids in suspension is 0.3

m/s and to keep silt and sand in suspension is about 0.6 m/s.

Maximum flow rate:This is the peak hourly flow. Such flow is used to determine the hydrauliccapacity of the treatment plant and collection system.

Design flow rate:Average daily flow at the end of the design period. Usually the average daily

flow is taken as the average over a continuous of 12 months period.

This design flow rate is used to determine organic loading and for sizing all

treatment units.

Flow Rates: Wastewater Treatment Plants


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Flow Sheet DiagramRiver Water Treatment Plant

Raw

waterEffluent

Chlorine

solution

FiltrationSettlingFlocculationMixingTraveling

Screen

Bar

Screen

Coagulant

GroundWater

Well

Aeration

Filters

Reverses Osmosis

Brine

Carbon bed

Ozonation

G.L

W.T

Filter

Add Mg

+

Add F

Filter

Bottled

Water

Bottle water Plant


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Example Industrial Wastewater Treatment Plant

Equalization TankInfluent

Aeration TankSettlingTank

Effluent

Air

Return sludge

Dispersed plug-flow activated sludge plant for an industrial wastewater

Chlorination


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Removal Efficiency

Treatment

Unit

Q,

Co

Q,

C

Removal efficiency = (Co-C)*100/Co

For example if Cois 100 mg/l and C is 10 mg/l then the

removal efficiency of the treatment unit is 90%.

Q= flow rate

Co= influent concentration

C = effluent concentration

Water Quality, pollution and treatment units.ppt

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