Chapter 7. Water Quality

Dr. BUNRITH SENG

Chapter 7

Water Quality

Mobile : +81 (0) 80 3259 9952

E-mail: [email protected]; [email protected]

Department of Civil Engineering, Zaman University

No. 8, St. 315, 12151 Phnom Penh, Cambodia

Zaman University Department of Civil Engineering

No. 8, St. 315, 12151 Phnom Penh, Cambodia

2

Important Water Quality Parameters

Dissolved Oxygen/Oxygen demand

Solids

Nitrogen

Infectious bacteria and viruses

Water quality parameters

3

Dissolved Oxygen

The measurement of the rate at which this oxygen is used by microorganisms decomposing organic matter.

Theoretical oxygen demand (ThOD)

Biochemical oxygen demand (BOD)

Chemical oxygen demand (COD)

4

Dissolved Oxygen (Cont.)

Theoretical oxygen demand (ThOD)

The oxygen demand for the decomposition of pure materials can be estimated from stoichiometry, assuming that all the organic material completely decomposes.

CaHbOc + O2 CO2 + H2O

CaHbNc Od + O2 CO2 + H2O + NH3

ThOD = C-ThoD + N-ThOD

C-ThOD is due to the decomposition of the carbonaceous (organic) material and N-ThOD is due to the stabilization of nitrogenous material (NH3 to NO3

-)

5

Example1: What is the theoretical oxygen demand in mg/L for a

1.67x10-3 molar solution of glucose, C6H12O6, to decompose completely?

Solution:

O6H 6CO 6O OHC 2226126

1 mol 6 mol

1.67 mol x ?mol 2O of mol 02.101

667.1

x

1 mol of O2 = 16x2 =32 g

L

mgO 321 32 02.10 2

2Om


6


Example2: What is the theoretical oxygen demand in liters of air for

a 300 mg/L solution of methylamine, CH3NH2, to decompose completely?

Solution:

32225 NH OH CO 1.5O NCH

31 g 1.5x32 g

0.3 g x g Lgx /O 4645.0

31

323.05.12

1 mol of O2 = 22.4 L O2

1 L of Air = 0.21 L O2

221.0

14.22

32

4645.0

O

air

L

L

mol

LmolThODC

solution

air

L

LThODC 55.1

7


OH HNO 2O NH 2323

Solution (cont.):

17 g 2x32 g

0.3 g x g

solutionO

air

LL

L

mol

LmolThODN airL

06.221.0

14.22

1

23.0

2

ThOD-N ThODCThOD

Total Oxygen Demand

solutionair/LL 61.306.255.1ThOD

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Biochemical oxygen demand (BOD)

The measure of the amount of oxygen required by aerobic bacteria and other microorganisms to stabilize decomposable organic matter.

A very low rate of O2 consumption would indicate:

Contamination is absent,

The available microorganisms are uninterested in consuming the available organics, or

The microorganisms are dead or dying.

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BOD Bottle 300 mL

BOD Measurement


The standard BOD test is run in the dark at 20oC for 5 days (BOD5).

Dark: algae may be presented and will produce O2 in

the bottle if light is available. 20oC: The rate of oxygen consumption is

temperature dependent. 5 days: Standard duration (it can be measured

shorter or longer than 5 days).

BOD is a difference of DO at initial and final day of the measurement.

FI DODOBOD Where: DOI : Initial DO, mg/L DOF : Final DO, mg/L

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BOD Measurement

Sample A:

FI DODOBOD

mg/L 628 BOD

Sample B:

mg/L ?08 BOD

BOD of sample B is greater than 8 mg/L. It must be diluted.

Sample C: mg/L 401048 BOD

Sample B is diluted with distilled water at a ratio 1:10.

Note:

mg/L 2FDO

mg/L 2DO

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Example: The five-day BOD of an influent to an industrial

wastewater treatment plant is expected to be about 800 mg/L based on similar wastewaters. What dilutions should be used in a five-days BOD test?

Solution:

Assume that o The saturation is about 10 mg/L o The remaining at least 2 mg/L in the bottle

Then, The drop BOD should be 10 – 2 = 8 mg/L At least 2 mg/L of DO is to be used

Average

1008

800D

4002

800D

Dilution Factor

200D

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The reaction in BOD bottle

CONSUMED

DO of Rate

PRODUCED

DO of Rate

OUT

DO of Rate

IN

DO of Rate

DACCUMULATE

DO of Rate

CONSUMED

DO of Rate

DACCUMULATE

DO of Rate

rVVdt

dz

Where: z : Dissolved oxygen, mg/L

z0: Initial dissolved oxygen, mg/L

t : Time

V: Volume of BOD bottle, mL

r: Reaction rate

zkdt

dz1

First-ordor reaction

tkezz 1

0

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Balance of Oxygen in the Bottle

yzL Where: y : DO already used or demanded at any time, t, mg/L

z : DO still required to satisfy the ultimate demand, mg/L

L : ultimate demand for oxygen, mg/L

zyL

tkeLyL 1

0

)1( 1tkeLy

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Chemical oxygen demand (COD)

A laboratory method that essentially determines the ThOD. This include both biodegradable and nonbiodegradable organic matters.

Sample + K2Cr2O7 + H2SO4

Heating

3 hours

15

10-3m 1 m

Colloidal Suspended Dissolved

Solid Particle Size

• Can be removed by a membrane or glass-fiber with nominal pore size of 1.2m

• Consists of organic and inorganic matters

• Can be removed by sedimentation

• Can be removed by a membrane


• Hardly/impossibly be removed by sedimentation

• Can be removed by a membrane


• Hardly/impossibly be removed by sedimentation

Solids

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3 type of solid determinations

o Total solids (TS)

o Total suspended solids (TSS)

o Total dissolved solids (TDS)

o Total suspended solids (TSS)

o Volatile suspended solids (VSS)

o Fixed suspended solids (FSS)

Total suspended solids

FSSVSSTSS

Total dissolved solids

o Total dissolved solids (TDS)

o Volatile dissolved solids (VDS)

o Fixed dissolved solids (FDS)

FDSVDSTDS

TDSTSSTS

Solids (Cont.)

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Experimental Procedure

Sample Filter with Glass fiber ( = 2m) (V mL)

Retained on the filter

Filtrate

Drying Owen

TDS (m1)

TSS (m`1)

Burning

Furnace of 530-550oC for 15-20 min

180 oC for 1h

103-105oC for 1h

FDS (m2)

FSS (m`2)

V

mmLmgVSS

`

2

`

1)/(

V

mmLmgVDS 21)/(

Solids (Cont.)

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Solids (Cont.)

Evaporating Dish

Glass fiber filter

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Example: A laboratory runs a solids test. The weight of the crucible

= 48.6212g. A 100 mL sample is placed in the crucible and the water is evaporated. The weight of the crucible and dry solids = 48.6432 g. The crucible is placed in a 600oC furnace for 24hr and cooled in a desiccators. The weight of the cooled crucible and residue, or unburned solids = 48.6300 g. Find the total, volatile and fixed solids.

Solution:

Solids (Cont.)

mg/L 22010

100

6212.486432.48 6

mL

gTS

mg/L 8810

100

6212.486300.48 6

mL

gFS

mg/L 132 88220 VS

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o Nitrogen is the largest single component of the earth’s atmosphere (78.08% by volume, 75.5% by weight) and their compounds play a vital role in water resources, in the life processes of all living organisms

o Nitrogen is an essential nutrient for biological growth, normally comprising about 12-14% of the mass of cell protein.

o Forms of nitrogen in the environment range from organic and ammonium nitrogen (oxidation state minus 3), through nitrogen gas (zero), to nitrite (plus 3) and nitrate (plus 5).

o Organic and ammonium nitrogen are the main forms present in municipal wastewater and are often measured together as Total Kjeldahl Nitrogen (TKN). Total organic nitrogen present is often such that during biological treatment it is all used in cell synthesis.

Org-N = TKN ─ NH4+

Nitrogen

Overview

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Nitrification

Denitrification

Nitrogen (Cont.)

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Nitrogen (Cont.)

Measurement

A photometer used for measuring light penetration through a colored sample

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Bacteriological Measurements

Waterborne Diseases

Typhoid

Cholera

Shigellosis

Enteroviral diseases

Giardiasis

Cryptosporidiosis

Salmonellosis

Hepatitis

Others

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Bacteriological Measurements (Cont.)

The bacteriological quality of pathogenic organisms in water is commonly measured the Coliforms (150 strains of E-coli).

Coliforms (E-coli) were chosen to be the indicator organisms because:

Normal inhabitants of the digestive tracts of warm-blooded animals

Plentiful and hence not difficult to find

Easily detected with a simple test

Generally harmless except in unusual circumstances

Hardy surviving longer than most known pathogens

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The capture of gas in a tube where lactose is fermented by coliform

organisms.

- No coliforms + Have coliforms

Bacteriological Measurements (Cont.)

Laboratory Testing

Petri dish culture (cell culture plating)

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Drinking Water Quality Standard

Drinking water quality by EPA under the Safe Drinking Water

Act (SDWA)

USA Standard

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Drinking Water Quality Standard (Cont.)

Drinking water quality by EPA under the Safe Drinking Water Act (SDWA)

USA Standard

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Drinking Water Quality Standard (Cont.)

Drinking water quality

standard

CAMBODIA

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Wastewater Discharge Standard

No Parameters Unit Allowable limits for pollutant substance

discharging to

Protected public water

area

Public water area

and sewer

1 Temperature 0C < 45 < 45

2 pH 6 – 9 5 - 9

3 BOD5 ( 5 days at 200 C ) mg/l < 30 < 80

4 COD mg/l < 50 < 100

5 Total Suspended Solids mg/l < 50 < 80

6 Total Dissolved Solids mg/l < 1000 < 2000

7 Grease and Oil mg/l < 5.0 < 15

8 Detergents mg/l < 5.0 < 15

9 Phenols mg/l < 0.1 < 1.2

10 Nitrate (NO3 ) mg/l < 10 < 20

11 Chlorine ( free ) mg/l < 1.0 < 2.0

12 Chloride ( ion ) mg/l < 500 < 700

13 Sulphate ( as SO4 ) mg/l < 300 < 500

14 Sulphide ( as Sulphur ) mg/l < 0.2 < 1.0

15 Phosphate ( PO4 ) mg/l < 3.0 < 6.0

Effluent standard for pollution sources discharging wastewater to public water areas or sewer

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Category I

The sources of pollution of category I

that are subject to the prior permit from

the Ministry of Environment when the

amount of their effluent exceed ten

cubic meter per day ( 10 M3 /day ) but

not including the amount of water

volume used for cooling the engine.

Category II

The sources of pollution of category II

that shall be necessarily required to apply

for the permission from the Ministry of

Environment.

No Type of pollution sources Category

1 Canned food and meat manufacturing I

5 Flour manufacturing I

6 Sugar manufacturing I

7 Pure drinking water manufacturing I

15 Cigarette manufacturing I

16 Garment manufacturing without

chemical washing

I

17 Hotel I

18 Restaurant I

19 Animal farm I

20 Slaughter – house I

21 Garage and car cleaning I

25 Sewage treatment plant I

37 Leather manufacturing II

38 Soap and detergent manufacturing II

40 Landfill site II

41 Textile or synthetic textile II

43 Pulp and paper manufacturing II

Pollution sources required having a permission from Ministry of Environment before discharging or transporting their wastewater

Wastewater Discharge Standard (Cont.)

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Water Quality Standard in public water areas for bio-diversity conservation

No Parameter Unit Standard Value

1 pH mg/l 6.5 – 8.5

2 BOD5 mg/l 1 – 10

3 Suspended Solid mg/l 25 – 100

4 Dissolved Oxygen mg/l 2.0 - 7.5

5 Coliform MPN/100ml < 5000

1- River

2- Lakes and Reservoirs


1 pH mg/l 6.5 – 8.5

2 COD mg/l 1 – 8

3 Suspended Solid mg/l 1 – 15

4 Dissolved Oxygen mg/l 2.0 - 7.5


6 Total Nitrogen mg/l 1.0 – 0.6

7 Total Phosphorus mg/l 0.005 – 0.05


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1 pH mg/l 7.0 – 8.3

2 COD mg/l 2 – 8

4 Dissolved Oxygen mg/l 2 - 7.5


5 Oil content mg/l 0

6 Total Nitrogen mg/l 1– 1.0

7 Total Phosphorus mg/l 0.02 – 0.09

3- Costal Water

Water Quality Standard in public water areas for bio-diversity conservation (Cont.)


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1 Carbon tetrachloride µg/l < 12

2 Hexachloro-benzene µg/l < 0.03

3 DDT µg/l < 10

4 Endrin µg/l < 0.01

5 Diedrin µg/l < 0.01

6 Aldrin µg/l < 0.005

7 Isodrin µg/l < 0.005

8 Perchloroethylene µg/l < 10

9 Hexachlorobutadiene µg/l < 0.1

10 Chloroform µg/l < 12

11 1,2 Trichloroethylene µg/l < 10

12 Trichloroethylene µg/l < 10

13 Trichlorobenzene µg/l < 0.4

14 Hexachloroethylene µg/l < 0.05

15 Benzene µg/l < 10

Water Quality Standard in public water areas for public health protection


Documents

Chapter 7. Water Quality