cel 212- environmental engineering 2nd sem 2012-13web.iitd.ac.in/~arunku/files/cel212_y13/water...

CEL 212- Environmental Engineering2nd Sem 2012-13

Dr. Arun Kumar

Week 2 Lectures (Jan 8th, 8th, and 11th)[email protected]

January 8, 2013 (C) Arun Kumar, IIT Delhi 2

Physical Water Quality Parameters

• Water characteristics that can be perceived by senses

1. Turbidity

2. Color

3. Suspended solids

4. Taste

5. Temperature

• Show physical samples ???


Turbidity-Introduction• “Turbid” indicates the presence of suspended

matters in water.

• “Turbidity” may by caused by colloids to coarse dispersions. Other sources are of inorganic and organic nature.

• It is important due to following aspects:– Aesthetics

– Filterability: Water with high solids content is hard to filter through filter and thus it becomes difficulty to water treatment using filtration.

– Disinfection: This process is used to kill microorganisms and thy can hide among suspended matters. These suspended materials reduce the disinfection potential of different disinfectants, such as chlorine, ultra-violet radiation, ozone etc.


Turbidity-Measurement

• Uses principles of nephelometry:

– Here a light source illuminates the sample

and one or more photoelectric detectors are

used with a readout device to indicate the

intensity of scattered light at right angles to

the path of the incident light.

– Formazin suspension is used as a standard

– Turbidity as low as 0.02 NTU (u.e.,

Nephelometric turbidity units) (here: 40

NTU=40 Jackson candle turbidity units (JTU)


Turbidity-Application of Data

1. Water supply:

• This info is used to decide if water is good as a

source drinking water and if it requires any further chemical treatment, etc. This measurements

indicate effectiveness of chemical treatment in a drinking water treatment plant (DWTP).

2. Domestic and industrial waste treatment:

• This measurement is used to determine

effectiveness of wastewater treatment plant (WWTP) for suspended solids removal. Using this

measurement, chemical dosage in chemical

treatment processes can be estimated.


Turbidity-Measurement

• Uses principles of nephelometry:

– Here a light source illuminates the sample

and one or more photoelectric detectors are

used with a readout device to indicate the

intensity of scattered light at right angles to

the path of the incident light.

– Formazin suspension is used as a standard

– Turbidity as low as 0.02 NTU (u.e.,

Nephelometric turbidity units) (here: 40

NTU=40 Jackson candle turbidity units (JTU)


Turbidity-Think About It!

• What things cause turbidity in:

– (1) river water during a flash flood,

– (2) polluted river, and

– (3) domestic wastewater

• Why turbidity cannot be correlated with the weight concentration of suspended matter in water samples?


Color-Introduction• Source of coloring material: organic matter such as

leaves, etc. at various stages of decomposition.• Tannin, humic acids and lignin are primary organic

molecules constituting color to a solution. Iron also contributes color to a solution (due to ferric humate).

• Natural color comes due to negatively charged colloidal particles.

• It is important due to following aspects:– Aesthetics

– Disinfection: Organic molecules responsible for producing color are oxidized due to chlorine (one of the many disinfectants) andform chlorine-substituted organic compounds, some of them have been reported carcinogens also (i.e., cancer causing). Thus it reduces effectiveness of chlorine to kill microorganisms present in water.


Color-Measurement• Sometime pretreatment of samples is required to remove

suspended material to measure color of a sample.

• Potassium chloroplatinate (K2PtCl6) tinted with small amounts of cobalt chloride gives color similar to natural color and thus this combination is used as a standard for deciding degree of color in a sample.

• Color produced by 1 mg/L of platinum (as K2PtCl6 ) is used as the standard unit of color.

• Procedure:– Make different dilutions of 500 mg/L Pt, with cobalt added and

compare samples with different diluted standard to provide rangefor color in terms of Pt concentration.


Color-Application of Data

1. Useful to indicate absence of color in water used for domestic supplies and industrial consumption

2. Color is used to indirectly determine the trihalomethane formation potential in a water during the chlorination process.


Color-Think About It!

1. Discuss causes of color in water.

2. What is “apparent” and “true” color?


pH-Introduction• It indicates the intensity of the acid or alkaline

condition of a solution.

• It is used to express hydrogen-ion activity in a solution.

• Useful for all wet-chemistry reactions where water molecule is involved.

• pH = -log10 [H+], where [H+] represent hydrogen ion concentration (dilute solutions)– For pure water at 25degC, Kw =10-14

– So pH=pOH = 7 (here pOH =-log10 [OH-]; pH+pOH=pKw)

– These values are temperature-dependent as it affects Kw.


pH-Measurement

• Hydrogen electrode is used to measure hydrogen

ion activity.

• Only for dilute solutions, concentration can be

assumed to be equal to activity.

• In this course we assume dilute solution, unless it is mentioned otherwise.

• Acid range: pH between 0 and 7

• Alkaline range: pH between 7 and 14


pH-Think About It!

1. Show relationship between pOH and hydroxyl ion concentration.

2. A decrease in pH of one unit represents how much of an increase in hydrogen-ion concentration?

3. Why pH is important in wet-chemistry


Suspended Solids• Total demand depends on following requirements:

– Residential demand

– Commercial demand

– Industrial demand

– Fire-fighting demand

– Public use

– Water lost or unaccounted for

• It depends on following factors:– Climate

– Geographic location

– Size, population and economic condition of community,

– Extent of industrialization

– Metered water supply, cost of water, supply pressure


pH• Total demand depends on following requirements:

– Residential demand

– Commercial demand

– Industrial demand

– Fire-fighting demand

– Public use

– Water lost or unaccounted for

• It depends on following factors:– Climate

– Geographic location

– Size, population and economic condition of community,

– Extent of industrialization

– Metered water supply, cost of water, supply pressure


Odor

• River/stream water

• Lake water

• Ground water (Tube well water)

• Rain water

• Wastewater effluent (treated for human

consumption)

– An effort towards reuse and recycle!

– Is it acceptable to use it for human consumption?


Color

• Say one person consumes=X liters per day (i.e., “X”lpcd( a short form of liters per capita per day)

• Total number of population in a community =“P”

• Total daily water demand = (X) *(P) liters per day

• Say amount of water required for duration = “T” days

• Total amount of water required (Vtotal)= (X)*(P)*(T) liters

• The water source should have this much (i.e.,Vtotal) to be considered as a potential water source.


Chemical Water Quality Parameters

• Water characteristics that involves chemical/biological reactions

1. Alkalinity

2. Acidity

3. Chemical oxygen demand (COD)

4. Biological oxygen demand (BOD)

5. Total organic carbon (TOC)

6. Theoretical oxygen demand (ThOD)


Alkalinity

• Per capita demand is different in normal

conditions and in drought conditions.

• Water demand also fluctuates

– Seasonally (maximum demand in July and August)

– Daily (more for working days than holidays)

– Hourly (more in morning and evening per day, i.e.,

two hours of peak demand over a 24-hour duration)


Acidity

• But, what about water quality of this water source? What if this water source doesn’t have good water and we might need to provide further treatment?– Leads to the consideration for water quality aspect of a given water

source!

• Among different water source types, consider following for evaluating their potential– Levels of different water quality parameters

– Amount of treatment required to meet water quality characteristics for the desired use

(The water quality characteristics are improved depending on water’s final usage and thus, its important to know the final use of the water)

• Overall: Water quality and available water volume-Both aspects should be considered during selection of a particular water source for a particular type of water usage.


Hardness









Chemical Oxygen Demand









Dissolved Oxygen









Biological Oxygen Demand









Total Organic Carbon









Theoretical Oxygen Demand









Microbial water quality parameters

• Fecal coliforms

• Total coliforms

• Coliphage

• Total culturable count (in terms of colony forming units: CFU)

cel 212- environmental engineering 2nd sem 2012-13web.iitd.ac.in/~arunku/files/cel212_y13/water...

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