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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