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September 6, 2016 Arun Kumar ([email protected])
1
(August 31st/Sep 2nd/Sep 5th, 2016)
by Dr. Arun Kumar ([email protected])
Lecture 7: DO Sag Curve-
Additional/Water Treatment Plants
Objective: To apply DO sag curve information for regulation purposes; learn water treatment plant schematic
1.Effect of pollution on DO sag curve
September 6, 2016 2
Example 1: Multiple drains entering into river AA
September 6, 2016 3
0
1
2
3
4
5
6
7
0246810121416182022
DO
(m
g/L
)
Upsteam distance from Okhla Barrage (km)
Simulated
Observed
September 6, 2016 4
0
10
20
30
40
50
60
0246810121416182022
BO
D (m
g/L
)
Upsteam distance from Okhla Barrage (km)
Simulated
Observed
Question
• Which region is not safe for aquatic species (required DO=4mg/L)?
• Should we do something in river? Or in drain?
• Which parameter to vary and how?
• How to calculate % treatment required in drain?
• What information are required?
September 6, 2016 5
2.Change in Nitrogen form in a polluted river under aerobic conditions
September 6, 2016 6
Fate of N-based compounds in river water
• The figure indicates the trend of inter-conversion
of different forms of N.
• With time, one can find different forms of N
present in water (ex: ammonia-N; nitrite-N).
• The form of nitrogen detected in water can
indirectly tell about time elapsed since
introduction of N-based pollution in river.
• One of the indicators of human fecal pollution
September 6, 2016 7
Modification steps
• Its better to control pollution in drain instead of
doing in river itself.
• Polluter can reduce BOD or COD upto desired
level so that drain water when mixed with river
water do not exceed the required receiving
body standard for DO and BOD.
September 6, 2016 8
Treatment method
• For treatment, the polluter has to decide about
type of treatment required (chemical or
biological or a combination of these two
methods)
• For oxygen demanding wastes (high BOD/COD
value), generally biological method (such as
aerobic process; anaerobic process) is preferred
over chemical methods (such as oxidation).
September 6, 2016 9
Treatment method
• For oxygen demanding wastes (low to medium
BOD/COD value), first chemical method is used
to make waste biodegradable and then
biological method is used.
• The first step of using chemical method can
improve BOD/COD value of oxygen demanding
waste and can help in subsequent biological
process.
September 6, 2016 10
Use of information on CPCB
website• Water quality information for different
water sources
• Water quality criteria
September 6, 2016 11
Water Information on CPCB Website
September 6, 2016 12
See BOD and Total coliform trends
September 6, 2016 13
Water Quality Standard on CPCB
Website
September 6, 2016 14
September 6, 2016 Arun Kumar ([email protected])
15
(August 31st, 2016)
by Dr. Arun Kumar ([email protected])
Lecture 8: Water Treatment Plants
Objective: To understand water treatment unit processes and their usage
Step 1. List water quality characteristics which need to be removed
• Parameters:
– Ions (arsenate; chromate ions;nitrate)
– Organic compounds (pesticides, etc.)
– Pathogens (viruses, if we have human fecal pollution)
– Solids (depends if there is a fracturing in subsurface)
– Gases(methane, etc.)
September 6, 2016 16
Step 2. Identify unit(s) which can remove at least one type of contamination
• Ions (removal by: adsorption; coagulation-
flocculation; chemical precipitation; bio-adsorption;
membrane process)
• Organic compounds (degradation/removal by:
oxidation; adsorption; biodegradation; reduction-
oxidation; irradiation; membrane process)
September 6, 2016 17
Step 2 contd.
• Pathogens (killed by : adsorption; coagulation-
flocculation; chemical precipitation; disinfection;
boiling; irradiation; membrane process)
September 6, 2016 18
Step 2 contd.
• Solids (removal by : settling; filtration; membrane
process)
• Gases (removal by) : aeration; adsorption;
solubilization)
September 6, 2016 19
Example 1: Groundwater �Drinking water
September 6, 2016 20
September 6, 2016 21
Answer: Treatment schematic (GW� Potable
drinking water)
• Raw Ground water � aeration chamber �
Softening unit � Filtration with chlorination
�Disinfection � Storage
• See sequence of units used
• Chemical is required to be added
• Water is treated
• Chemical sludge is produced
September 6, 2016 22
Units used for (GW� Potable drinking water)
• Aeration chamber (to remove gases; using air)
• Softening unit (to remove cations; using softener and/or cation exchangers)
September 6, 2016 23
Treatment schematic (GW� Potable drinking
water)
• Filtration with chlorination (to remove solids; to kill microbial growth on filter unit surface)
• Disinfection (to kill microorganisms before water is supplied for public consumption)
• Storage
September 6, 2016 24
Question 1: Yamuna River Water �Drinking water
• Think for 5 minutes for two steps.
• Step 1: water quality characteristics determination
• Step 2: selection of units, their order
September 6, 2016 25
Answer: Yamuna River Water �Drinking water
September 6, 2016 26
schematic contd.
September 6, 2016 27
Treatment schematic (SW� Potable drinking
water)
• Sequence of unit processes: pre-sedimentation
�mixing, flocculation,
settling�filtration�adsorption �disinfection
• Function of unit processes: solids removal �
removal of ions, and solids using chemical
addition�removal of smaller particles �removal of
organic compounds and ions�oxidation of oxygen-
demanding wastes and chemical killing of
pathogens in water
September 6, 2016 28
(SW� Potable drinking water) contd..
• Chlorine is added in sedimentation and filtration
tank to avoid microbial growth
• Chorine is used as a oxidizing agent and
disinfection solution also.
September 6, 2016 29
variations
• River water
• Rw+domestic wastewater
• Industrial wastewater
• Domestic ww+industrial ww
• RW+DW+industrial wastewater
September 6, 2016 30
Treatment schematic (Industrial water� Potable
drinking water)
• Industrial water: example: chromium ions;
suspended solids; high COD; color
• Sequence of unit processes:
– Option 1: pre-sedimentation �mixing, coagulation-
flocculation, settling�adsorption (for removing chromium
ions)�advanced oxidation method (for removing organic
compounds)
– Option 2: pre-sedimentation �mixing, coagulation-
flocculation, settling�adsorption (for removing chromium
ions as well as organic compounds)
September 6, 2016 31
Treatment schematic (Domestic wastewater
+Industrial water� Potable drinking water)
• Domestic wastewater+Industrial water: example: nutrients,
pathogens, BOD, chromium ions; suspended solids; high
COD; color
• Sequence of unit processes:
– Option 1: pre-sedimentation �mixing, coagulation-
flocculation, settling�ion exchange (for removing
ions)�adsorption (for removing chromium
ions)�advanced oxidation method (for removing organic
compounds)� disinfection
– Option 2: pre-sedimentation �mixing, coagulation-
flocculation, settling�adsorption (for removing chromium
ions, nutrients as well as organiccompounds)�disinfection
September 6, 2016 32
Treatment schematic (RW+Domestic wastewater
+Industrial water� Potable drinking water)
• RW+Domestic wastewater +Industrial water: example: nutrients,
pathogens, BOD, chromium ions; suspended solids; high COD;
color (reduced concentration due to dilution with river water)
• Sequence of unit processes:
– Option 1: pre-sedimentation �mixing, coagulation-flocculation,
settling�ion exchange (for removing ions)�adsorption (for
removing chromium ions)�advanced oxidation method (for
removing organic compounds)� disinfection
– Option 2: pre-sedimentation �mixing, coagulation-flocculation,
settling�adsorption (for removing chromium ions, nutrients as
well as organic compounds)�disinfection
September 6, 2016 33
Question 2: GDW to Gardening water
• Which parameters do we need to remove?
• Which unit processes do we need for making
gardening water from groundwater? Is the order
of unit process relevant here?
• How does the schematic of treatment of GDW to
Gardening water differ with that of GDW-
Drinking water?
September 6, 2016 34
Answer:GDW to Gardening water
• Removal of
– Excess metal ions
– Alkalinity
– Hardness
• Unit process:
– Ion exchanger
– Adsorber
September 6, 2016 35
Difference (GDW to Gardening water vs. GDW to
Drinking water)
• Drinking water requires higher removal of
pathogens, organic compounds than that is
required for producing gardening water
• Additional units: disinfection chamber; adsorber
are required to add in water treatment plant
treating GDW for producing gardening water.
September 6, 2016 36
Question 3: Injection of gardening
water runoff in soil: Requirements?
• We produced gardening water from GDW.
• Now, if we inject garden water runoff to soil,
would this be ok?
• Which parameters do we need to worry?
• Do we need to do treatment before we can inject
the water? Will it depend on soil type, depth to
water table, etc.?
September 6, 2016 37
Injection of gardening water runoff in soil:
• Runoff should not have excess metal ions,
organic matter, pathogens, alkalinity and acidity
so that it should not affect soil characteristics
September 6, 2016 38
Question 4: Comparison
• Why do water treatment schematics for GDW�
DW and SW� DW differ?
• Can one treatment plant treat GDW as well as
SW for producing DW?
• Answer:
– It depends on sequence of unit processes and their
abilities in removing additional parameters upto
desired levels.
September 6, 2016 39
Example 3. Domestic wastewater � Discharge
water to river
• Sequence of unit processes: stabilization
tank�sedimentation �biological
process�secondry settling � nitrifier
unit�denitrifier unit �disinfection�discharge water
suitable for river
• Function of unit processes: making incoming flow
rate uniform �solid removal�breakdown of organic
compound �settling of microbial biomass
�removal of ammonium ions �removal of nitrate
ions �killing of microorganisms
September 6, 2016 40