chapter 2-water quality

Assignment 1 (individual)

Please state and briefly discuss five acts in laws and legislation related to

the environmental (15 marks)

CHAPTER 2

Water Quality Standards and

Parameters

BFC 3103ENVIRONMENTAL ENGINEERING

Content PART 1: INTRODUCTION

i) Beneficial Water Uses ii) Water Resources PART 2:WATER QUALITY i) Definition ii) Objectives iii) Water Quality Parameters PART 3: WATER QUALITY PARAMETERS

i) Physical ii) Chemical iii) Microbiological


PART 1INTRODUCTION

i) Beneficial Water Uses ii) Water Resources


i) Beneficial Water Uses

Municipal Uses Agricultural Uses Industrial Uses Rural Uses


ii) Water Resources

1. Snow / Rain2. Surface Water i) Watershed Management ii) Lake /River /Reservoir iii) Intake Structure iv) Pump v) Treatment Facilities


Continues….3. Imported water i) Transmission Pipeline ii) Treatment Facilities4.Groundwater i) Basin Management

Natural and artificial recharge Quality Control

ii) Wells


PART 2:

WATER QUALITY

i) Definitionii) Objective

iii) Water quality parameters


i) Water quality-definition

Is the technical term that is based upon the characteristics of water in

relation to guideline values of what is suitable for human consumption and

for all usual domestic purpose


ii) Objective of water quality

To control the discharge of pollutants so that water quality is not degraded to an unacceptable extent below the

natural background level


iii) Water environmental quality parameters

- Are the natural and man-made chemical, biological and microbiological characteristics of rivers, lakes and groundwaters.

- it provide important information about the health of a water body.


Are used to find out if the quality water is good enough for drinking water, recreation, irrigation and aquatic life.

These include chemical, physical and biological parameters


PART 3:

WATER QUALITY PARAMETERS


Water quality parameters

3. Biological parameters

1. Physical

parameters

2. Chemical parameters


1.Physical parameters- This parameters respond to the sense

of sight, touch, taste or smell

Suspended solid

temperature

colorodor turbidity


a)Turbidity Is a measure of the amount of particulate

matter that is suspended in water. Unit-NTU (Nephlometric Turbidity Unit)

Water that has HIGH turbidity appears CLOUDY/ OPAQUE.

HIGH turbidity can cause INCREASED of water TEMPERATURE

WHY???BFC 3103

ENVIRONMENTAL ENGINEERING

It is because…

- More suspended particles will absorb more heat which in turn lowers dissolved O2 levels.

- Such particles (ss – clay, silt, finely divided organic material, plankton) can also prevent sunlight from reaching plants below surface hence DECREASE the rate of PHOTOSYNTHESIS.

- So, LESS O2 is produced by plant


b) Temperature It is a major factor in determining which

species are present in the stream Temperature will impacts: i) the rates of metabolisme and growth of

aquatic organism ii) rate of plant photosynthesis iii) solubility of O2 in water iv) organism’s sensitivity to disease,

parasites and toxic materialsBFC 3103


Continues… Cool water tastes better Temperature affects rate of chemical

and microbiological reactions The most suitable drinking waters are

consistently cool and do not have temperature fluctuations of more than a few degrees

Groundwater and surface water from mountain area generally meet these criteria


c) Solids Total Solids (TS) TSS (Total Suspended Solids) Dissolved solids Volatile Solids Volatile Disolved Solids mg/l


d) color It is due to the presence of dissolved and

suspended matter (metallic ions, chemical pollutants, plankton and plant pigments from humus and peat.

These substance do not threaten stream water quality, but indicate INCREASED DEVELOPMENT in watershed.


Continues… Dissolved organic material from humic

substances generally lend a brown or ‘tea’ color to water

Dissolved organic material from vegetation and certain inorganic matter may cause color in water


Continues… Taste problems relating to water could be

indicators of changes in water sources or treatment process

Inorganic compound such as magnesium, calcium, sodium, copper, iron and zinc are generally detected by taste of water.


e) Taste & Odor Caused by foreign matters such as organics

compounds, inorganic salts, bacteria, algae and dissolved gases

Measurement: Threshold Odor Number (TON) Examples:

i) addition of ammonia to form monochloramine in the pipes

ii) excessive manganese & iron present in the finished water.

** manganese & iron often found in groundwater supplies where the overall quality of the water is good but there is a high amount of soluble salt. These metals then react with O2 in the distribution system to produced the reduced and insoluble form of the metal**


2. Chemical parameters Chemical quality refers to general water

characteristics and dissolved mineral levels in the water

Due to certain industries and agricultural practices or from natural resources.


Continues… It is an important indicators of water quality;

humans, plants and animals Chemical attributes of water can affect aesthetic

qualities such as how water looks, smells and tastes.

Assessment of water quality by its chemistry includes measures of many elements and molecules dissolved or suspended in the water


Continues… Chemical measures can be directly detect

pollutants such as lead and mercury Also used to detect imbalances within the

ecosystem. Such imbalance may indicate the presence of certain pollutant.

pH, alkalinity, hardness, nitrates, nitrites, and ammonia, phosphates, dissolved O2 and biochemical O2 demand are commonly measured chemical parameters


CHEMICAL PARAMETERS

pH

Dissolved oxygen(DO)alkalinity

hardness

Biochemical oxygen demand (BOD)

Nitrites and nitrates


Assignment (Individual) There are three major parameters in

determining the water quality. One of them is physical parameters. Please state and describe in details the other two major parameters. (15 marks)


Chemical parameters1) pH- It is a measure of the concentration of hydrogen

ions- The term pH was derived from the manner in

which the hydrogen ion concentration is calculated

- pH scale ranges from 0 to 14. A pH of 7 is considered to be neutral.

- Substances with pH of less than 7 are acidic; substances with pH greater than 7 are basic


Continues..affects chemical and biological

reactionsLow pH is corrosiveHigh pH cause deposits


2) Hardness- Stream water hardness is the total

concentration of cations, specifically calcium (Ca2+ ),magnesium (Mg2+), iron (Fe2+), manganese (Mg2+) in the water.

- Water rich in these cations is said to be ‘hard’. Stream water hardness reflects the geology of the catchment area.

- Sometimes it also provides a measure of the influence of human activity


Continues… For instance, acid mine drainage often

results in the release of iron into a stream. The iron produces extraordinarily high hardness is a useful water quality indicator.

Hardness is a reflection of the amount of calcium and magnesium entering the stream through the weathering of rock such as limestone (CaC03)


3) Alkalinity Is measured to determine the ability of a stream to

resist changes in pH. Alkalinity results from the dissolution of calcium

carbonate (CaC03) from limestone bedrock which is eroded during the natural processes of weathering

Alkalinity values of 20 -200 ppm are common in freshwater ecosystems. Alkalinity levels below 10 ppm indicate poorly buffered streams.

These stream are the least capable of resisting changes in pH, therefore they are most susceptible to problems which occur as a result of acidic pollutants


4) Nitrates, nitrites and ammonia Nitrogen is an essential nutrient that is required

by all plants and animals for the formation of amino acids.

In its molecular form, nitrogen cannot be used by most aquatic plants, therefore it must be converted to another form.

One such form is ammonia (NH3). Ammonia may be taken up by plants or oxidized by bacteria into nitrate (NO3

-) or nitrate (NO2). Of these two forms, nitrate is usually by the most important.


5) Biochemical oxygen demand (BOD)

It is a measure of the quantity of oxygen used by microorganisms (eg.aerobic bacteria) in the oxidation of organic matter.

In other words: BOD measures the change in dissolved oxygen concentration caused by the microorganisms as they degrade the organic matter.

High BOD is an indication of poor water quality


6) Dissolved oxygen (DO) It is an essential for the survival of nearly all

aquatic life and measured in mg/L If oxygen levels are high, it was presume

that pollution levels in the water are low. Conversely, if oxygen levels are low, one

can presume there is a high oxygen demand and that the body of water is not of optimal health


Continues… Levels of DO vary depending on factors including

water temperature, time of day, season, depth, altitude and rate of flow.

(i) water at higher temp and altitudes will have LESS DO. so, demand O2 will increased because at higher temp, the rate of metabolisme is increased.

(ii) at night, DO decreased as photosynthesis has stopped while oxygen consuming process such as respiration, oxidation

(iii) DO reaches its peak (HIGH) during the dayBFC 3103


3. Biological parameters

It is biomonitor: defined as an organism that provides quantitative information on the quality of the environmental around it.

It can be deduced through the study of the content of certain elements or compounds, morphological or cellular structure, metabolic-biochemical process behavior or population structure


Continues.. There are several types of bioindicators: (i) plant indicators - the presence or absence of certain plant or other vegetative

life in an ecosystem can provide important clues about the health of the environment

- lichens are organism comprising both fungi and algae. Lichens are found on rocks and tree trunks, and they respond to environmental changes in forest, including changes in forest structure conservation biology, air quality and climate

- The disappearance of lichens in a forest may indicate environmental stresses, such as high level of sulfur dioxide, sulfur-based pollutants and nitrogen oxides


Continues…(ii) Animal indicator and toxins - an increase or decrease in an animal

population may indicate damage to the ecosystem caused by pollutant. For eg; if population causes the depletion of important food sources, animal species dependent upon these food sources will also be reduced in number: population decline

- Submerged aquatic vegetation (SAV) provides invaluable benefits to aquatic ecosystems. It not only provides food and shelter to fish and invertebrates but also produces oxygen, trap sediment and absorbs nutrients such as nitrogen and phosphorus


Continues…(iii) Microbial indicators and chemical pollutants- Microorganisms can be used as indicators of

aquatic or terrestrial ecosystem health- Found in large quantities, microorganism will

produce new proteins, called stress proteins when exposed to contaminants like cadmium and benzene

- These stress proteins can be used as an early warning system to detect high levels of pollution


Continues…(iv) Macroinvertebrate bioindicators- Macroinvertebrate are useful and

convenient indicators of the ecological health of a waterbody or river. They are almost always present, and are easy to sample and identify

- Benthic refers to the bottom of a waterway. Example of benthic macroinvertebrates include insects in their larval or nymph form, crayfish, claims, snails and worms. Most live part or most of their life cycle attached to submerged rocks, logs and vegetation.


Continues…- The basic principle behind the study of

macroinvertebrates is that some a re more sensitive to pollution than others

- Therefore, if a stream site is inhabited by organism that can tolerate pollution and the more pollution-sensitive organisms are missing a pollution is likely


Microbiological Bacteria( coliform test) Virus Protozoa Algae


Bacteria Pathogenic bacteria causing cholera,

typhoid fever etc Indicator bacteria

Coliform Fecal Coliform( E. Coli)


Virus One virus can cause illness Hard to detect Specify treatment process

( disinfection dose and contact time) instead of measuring virus concentration


Algae Taste and odor Some algae cold be harmful to

animals fish birds


EFFECTS ON WATER QUALITY

1) Toxic inorganic

2) Nontoxic organic

3) Toxic organic


Toxic inorganic elements and radicals Arsenic, Mercury, Cadmium, Chromium,

Lead-- accumulates in body Industrial wastes and plumbing Lead and Copper Rule Nitrate--Blue baby Perchlorate ( ClO4

-) --Thyroid disorder, cancer


Nontoxic organics NOC ( Natural organic matter)

Decayed vegetation etc Form toxic disinfection by-products

with chlorine Lower concentrations up to 4 mg/l

may be removed by Enhanced Coagulation.


Toxic organicsCausing cancer, mutation or

miscarriage chlorinated hydrocarbons Chlorophenoxy herbicides Trihalomethanes VOC’s and SOC’s.


Other Contaminants Asbestos Radionuclides

Alpha and Beta radioactivity Uranium, Radium, Radon


WATER QUALITY MEASUREMENT

a) ThOD – theoretical oxygen demand

(i) It is the amount of O2 required to

oxidize a substance to CO2 and H2O

(ii) Calculated by stoichiometry if the chemical composition of the substance is known


Example:

Compute the ThOD of 108.75 mg/L of glucose (C6H12O6)

STEPS:

(i) write balanced equation for the reaction

(ii) Compute the grams molecular weights of the reactants

(iii) Determine ThOD


Exercise(5.1, 5.2, 5.3-in the text book)

1. Glutamic acid (C5H904N) is used as one of the reagents for a standard to check the BOD test. Determine the ThOD of mg/L of glutamic acid. Assume the following reaction apply:

C5H904N + 4.5O2 5CO2 + 3H2O + NH3

NH3 + 2O2 NO3+ H+ + H2O


b) BOD biochemical oxygen demand The actual BOD is LESS than ThOD due to

incorporation of some of carbon into new bacterial cells

The greater the amount of organic matter present, the greater the amount of oxygen utilized

It is indirect measurement of organic matter becoz we actually measure only the change in dissolved concentration caused by the microorganism as they degrade the organic matter


Continue..

a) BOD was calculated using the formula

Lo = oxygen equivalent of organic compound at time t = 0/ ultimate BOD

t=time

k=2.303 (K)

BODt = Lo(1-10-kt)


Exercises: Problems 5.4, 5.5 and 5.6 in the text book


Continue…

b) Thomas’ graphical method - Used to find BOD constant, k- Procedure:

i) Calculate the value of (t/BODt)1/3 for each day.

ii) Plot (t/BODt)1/3 versus t on arithmetic graph paper and draw the line of fit by eye


Continues….

iii) Determine the intercept (A) and slope (B) from the plot

iv) Calculate k and Lo using formula:

k = 6 (B/A) Lo = 1/ 6(A)2(B)


Exercise….

Problem 5.19, 5.20 and 5.21 from the text book.

Additional:

Please calculate the BOD after six days for each problem.


DO sag curve (page 373 text book)

-the concentration of DO in a river is an indicator of the general health of the river.

- All rivers have CAPACITY for self purification. (i) As long as the discharge of oxygen demanding

wastes is well within the self purification capacity, the Do level remain HIGH and a diverse population of plants and animals

(ii) As the amount of waste increase, the self purification capacity can be exceeded, causing detrimental changes in plant and animal life


continues….(iii) then, the stream losses its ability to clean itself

and the DO level DECREASES. (iv) when the DO drops below 4 to 5 mg/L,

most game fish will have been driven out.(v) If the DO is completely removed, fish and other

higher animals are killed or driven(v) The water become blackish and foul smelling as

the sewage and dead animal life decompose under anaerobic condition (without O2)


SO…… ABILITY TO ASSESS THE

CAPABILITY OF A STREAM TO ABSORB A WASTE LOAD is one of the major tools of water quality management.

HOW????

BY DETERMINING THE PROFILE OF DO CONCENTRATION

DOWNSTREAM FROM A WASTE DISCHARGE


To develop mathematical expression of DO sag curve…..- The sources of O2 and the factors affecting

oxygen depletion must be identified and quantified

- Significant SOURCE:

i) REAERATION from the atmosphere and photosynthesis from aquatic plants

- FACTORS effecting O2 depletion

i) BOD of the waste discharge

ii) BOD already in the river upstream of the waste discharge


continues…iii) DO in the waste discharge is usually less

than that in the river

SOThe DO at the river is LOWERED as soon

as the waste is added.iv) The respiration of organism living in the

sediments and respiration of aquatic plants


DO sag curve approach

Approach

Mass balance Heat balance

(1)Mass balance approach


Mass of DO in wastewater, QwDOw

Mass of DO in river after mixing, QwDOw + QrDOr

Mass of DO

in river QrDOr

continues…Mass of BOD after mixing:

QwLw + QrLrLw = ultimate BOD of the waste

water, mg/L

Lr = ultimate BOD of the river, mg/L


continues… The concentration of DO after mixing and

initial ultimate BOD after mixing, La


DO= QwDOw + QrDOr Qw + Qr

La = QwLw + QrLr Qw + Qr

Sum of wastewater and river flows

Lw & Lr:Ultimate

BOD

waste

river

Calculation: example

The town of State College discharge 18, 360 m3/d of treated wastewater into the Bald Eagle Creek. The treated wastewater has a BOD5 of 14 mg/L and a k of 0.12d-1 at 20˚C. bald Eagle Creek has a flow rate of 0.46 m3/s and ultimate BOD of 5.0 mg/L. The DO of the river is 6.7 mg/L and the DO of the wastewater is 1.0 mg/L. Compute the DO and initial ultimate BOD after mixing


Solution….

DO= QwDOw + QrDOr

Qw + Qr


(2) Heat balance

For TEMPERATURE consideration From fundamental principle of physics:

Loss of heat = gain of heat by by hot bodies cold bodies

(a) TEMPERATURE

Temperature after mixing:

Tf= QwTw + QrTr Qw + Qr

(b) Oxygen deficit

- it is the amount by which the actual dissolved oxygen concentration is less than the (saturation value) with respect to oxygen in the air

Is dependent on watertemp – it decreases as the

temp increases

D= DOs-DO

Oxygen deficit, mg/L Saturation concentration

of DO, mg/L

Actual Concentration of DO, mg/L

(c) Initial deficit

- Beginning of the sag curve: a point where a waste discharge mixes with the river

- Use the downstream temperature when determining the saturation concentration of DO

- Initial deficit- is calculated as the difference between saturated DO and the concentration of DO after mixing

Continues…

-equation for initial deficit:

Da = DOs - QwDOw + QrDOr

Qw + Qr

Initial deficit after river and wastehas mixed, mg/L

Saturation concentrationof dissolved oxygen at the

temperature of the riverafter mixing, mg/L

Exercise:

1)The town of State College discharge 18,400 m3/d of treated wastewater into the Bald Eagle Creek. The treated wastewater has a BOD5 of 10 mg/L and a k of 0.12/d at 20°C. Bald Eagle Creek has a flow rate of 0.45 m3/s and an ultimate BOD of 4.0mg/L. The DO of the river is 5.5mg/L and the DO of the wastewater is 1.5mg/L. Compute the DO and initial ultimate BOD after mixing.

exercise2) Calculate the initial deficit of the Bald

Eagle Greek after mixing with the waste water from the town of the State College (see Exercise 1 for data). The stream temperature is 10°C and the wastewater temperature is 10°C

**DOs can be determined from the table in Appendix A

(d) DO sag equation

-

D= oxygen deficit in river water after exertion of BOD for time, t, mg/LLa = initial ultimate BOD after river and wastewater have mixed, mg/LKd= deoxygenation rate constantKr = reaeration rate constantt=time of travel of wastewater discharge downstream, dDa = initial deficit after river and wastewater have mixed, mg/L

D = kdLa (e-kdt – e-krt) + Da(e-krt) kr - kd

continues… When kr = kd, the equation reduces to:

(where the terms are previously defined)

D = (kdtLa + Da)(e-kdt)

(e) Deoxygenation rate constant, kd

It defers from the BOD rate constant, k because there are physical and biological differences between a river and BOD bottle

In general, BOD exerted more rapidly in a river because of turbulent mixing, larger number of seed organism and BOD removal by organism

BOD rate constant, k rarely has a value greater than 0.7/day, kd may be as large as 7/day

continues… Equation for kd:

Kd=k + (v/H)ŋ

Deoxygention rateConstant at 20˚C,

day-1 Average speed of Stream flow, m/s

Average depth of Stream, m

Bed-activity coefficient

BOD rate constant Determined in lab at

20˚C, day-1

exercise

3) Determine the deoxygenation rate constant for the reach of Bald Eagle Greek (Exercise 1 and 2) below the wastewater outfall (discharge pipe). The average speed of the stream flow in the creek is 0.03 m/s. The depth is 5.0m and the bed activity coefficient is 0.35.

kT = k20 (θ)T-20

(f) Reaeration rate constant

kr = 3.9v0.5

H1.5

MANAGEMENT STRATEGY

Water quality management in rivers using the DO sag curve is to DETERMINE THE MINIMUM DO CONCENTRATION THAT WILL PROTECT THE AQUATIC LIFE IN THE STREAM.

DO standard is generally set to protect the most sensitive species that exist or could exist in particular river

continues….

That’s why DO sag equation can be solved to find the DO at the critical point.

If the DO at the critical point is LESS than standard, the streamcan adequately assimilate the

waste

continues… The ultimate BOD of the waste discharge

can be reduced, thereby La by:

1) Increasing the efficiency of the existing treatment process

2) Adding additional treatment steps

3) Reduce Da –by adding oxygen to the wastewater to bring it close to saturation prior to discharge

chapter 2-water quality

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