Lecture 7: DO Sag Curve- Additional/Water Treatment...

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


Water Information on CPCB Website


See BOD and Total coliform trends


Water Quality Standard on CPCB

Website


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.)


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)


Step 2 contd.

• Pathogens (killed by : adsorption; coagulation-

flocculation; chemical precipitation; disinfection;

boiling; irradiation; membrane process)


Step 2 contd.

• Solids (removal by : settling; filtration; membrane

process)

• Gases (removal by) : aeration; adsorption;

solubilization)


Example 1: Groundwater �Drinking water



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


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)


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


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


Answer: Yamuna River Water �Drinking water


schematic contd.


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


(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.


variations

• River water

• Rw+domestic wastewater

• Industrial wastewater

• Domestic ww+industrial ww

• RW+DW+industrial wastewater


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)



ions as well as organic compounds)


Treatment schematic (Domestic wastewater

+Industrial water� Potable drinking water)

• Domestic wastewater+Industrial water: example: nutrients,

pathogens, BOD, chromium ions; suspended solids; high

COD; color



flocculation, settling�ion exchange (for removing

ions)�adsorption (for removing chromium

ions)�advanced oxidation method (for removing organic

compounds)� disinfection



ions, nutrients as well as organiccompounds)�disinfection


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)


– 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


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?


Answer:GDW to Gardening water

• Removal of

– Excess metal ions

– Alkalinity

– Hardness

• Unit process:

– Ion exchanger

– Adsorber


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.


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.?


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


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.


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


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