engg.500 notes.docx

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Engg 500: Introduction to Environmental Engineering

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WATER CYCLE AND WATER QUALITY

Hydrology- Hydrology is the study of water and its movement along its various pathways within the

hydrological cycle. This is applied by engineers who use hydrological principles to compute river

flows from rainfall, water movement in soils form knowledge of soil characteristics, evaporation

rates from water balance or energy balance techniques.

The Water Cycle- The hydrological cycle is central to Hydrology. It is a continuous process showing constant state of

motion of water. Water evaporates from the earths oceans and water bodies and from land

surfaces. About seven times more evaporation occurs from oceans than from the earths land

surfaces. The evaporated water rises into the atmosphere until the lower temperatures alof

cause it to condense and then precipitate in the form most globally as rain but sometimes as

snow. Once on the earths surface waters flow into streams, lakes, and eventually discharges into

surface waters. Through evaporation from surface water or transpiration plants, water molecules

return to the atmosphere to repeat the cycle. The term evapotranspiration is used referring to

combined evaporation and transpiration usually exhibited by living plants. In general of 100 units

of rain that falls on grassland in temperature zones, 10 to 20 units will go to groundwater, 20-40

units will transpire and 40 to 70 units will become stream runoff.

Water never leaves the Earth. It is constantly being cycled through the atmosphere, ocean, and landThis process, known as the water cycle, is driven by energy from the sun. The water cycle is crucial to

the existence of life on our planet.

Evaporation-The sun heats up liquid water and changes it to a gas.Water that evaporates from Earthsoceans, lakes, rivers, and moist soil rises up into the atmosphere.

Condensation-As water (in the form of gas) rises higher in the atmosphere, it starts to cool and becomea liquid again.

Groundwater-water absorbed into the ground forming pockets of water. Most groundwater eventuallyreturns to the ocean.

Water runoff-Other precipitation runs directly into streams or rivers The earth has approximately 1.4 billion cubic kilometers of water either trapped underground on the

surface or in the atmosphere. More than 97% of this is salt water found in the oceans and seas and

more than 2% is fresh water frozen in the polar ice caps.


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WATER QUALITY

Water in nature is most nearly pure in its evaporation state. However it acquires impurities once condensed and

additional impurities are added as the liquid water travels through the remainder of the hydrologic cycle and

comes in contact with materials in the air and on or beneath the earths surface. In addition, human activities

contribute further impurities in the form of industrial and domestic wastes, agricultural chemicals, and othe

less obvious contaminants. These impure water returns to the atmosphere as relatively pure molecules through

evaporation.

It is the water quality in the intermediate states that is of great concern because it is the quality at this stages

that will affect human use of water. The impurities are accumulated in water throughout the hydrologic cycle

and as a result of human activities may be both suspended (larger particles) and dissolved from (molecules

ions). Colloids are also very small particles that are suspended but often exhibit many characteristics of dissolved

substances.

Water supplies:

1. Ground water Supplies- Ground water is an important direct source of water supply and a significant indirect source since

a large portion of the flow to stream is derived from subsurface water. Near the surface of theearth in thezone of aeration, soil pore the spaces contain both air and water. This zone may have

zero thickness in the swamplands and can be several hundred feet thick in arid regions. Moisture

from this zone cannot be tapped as water supply since this water is held on soil particles by

capillary forces and is not readily released.

- Below the zone of aeration is the zone of saturation, in which the pores are filled with waterWater within this zone is referred to asGroundwater. A stratum containing a substantial amount

of groundwater is called Aquiferand the surface of this saturated layer is known as the Water

Table. If the aquifer is underlain by the impervious layers, it is called an unconfined aquifer. If the

stratum containing water is trapped between two impervious layers, it is known as confined

aquifer.

2. Surface water Supplies- Surface water supplies are not as reliable as groundwater sources because quantities often

fluctuate widely during the course of a year or even a week, and the quality of surface water is

easily degraded by various sources of pollution.


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WATER QUALITY PARAMETERS

I. Physical Water-Quality Parameters1. Suspended Solidsconsists of inorganic and organic particles

Sources:

a) Inorganic Solidsclay, silt, other soil constituentsb) Organic Solidsplant fiber and biological solids (algal cells, bacteria, etc)

Impacts: Objectionable in water, aesthetically displeasing and provides adsorption sites for chemica

land biological agents

2. Turbiditya measure of the extent to which light is either absorbed or scattered by suspended materiain water. This is not a direct quantitative measure of suspended solids

Sources: erosion of colloidal matters such as clay, silt, rock fragments and metal oxides from soil,

vegetable fibers and microorganisms, soaps and detergents, emulsifying agents.

Impacts: aesthetically displeasing, provides adsorption sites for biological and chemical agents, cause

undesirable tastes and odor, impart color to natural water bodies, may interfere with light penetration

during photosynthesis, sediments and solid deposits also adversely affect the flora and fauna of thestreams

3. ColorPure water is colorless but water in nature is often colored by foreign substancesa) Apparent Colorcolor that is partly due to suspended matterb) True Colorcolor that which is contributed by dissolved solids that remain after removal of the

suspended matter

Sources: contact with organic debris such as leaves, conifer needles, weeds, or wood, water pick up

tannins, humic acid, and humates and takes on yellowish-brown hues. Iron oxides cause reddish water

Manganese oxides cause brown or blackish water. Industrial wastes: textile and dyeing operations, pulp

and paper production, food processing, chemical production, mining, refining, and slaughterhouse

operations add substantial color to water in receiving streams.Impacts: Not aesthetically acceptable to general public. Highly colored water is not suitable for laundry

dyeing, papermaking, beverage manufacturing, diary production, and other food processing, textile and

plastic production

4. Taste and OdorSubstances that produce an odor in water will almost invariably impart a taste as wellSources: minerals, metals and salts from soil, end products of biological reactions, and constituents o

wastewater. Inorganic substances are more likely to produce taste unaccompanied by odor. Alkaline

materials imparts bitter taste to water, metallic salts impart salty or bitter taste. Organic susbstances

most likely produce both taste and odor. Biological decomposition of organic matter may result to taste

and odor producing liquids and gases. Certain species of algae also secrete oily substances which may

result to taste and odor.

Impacts: aesthetically displeasing, health threat (since carcinogens may be produced when some

organics react with chlorine during disinfection)

5. TemperatureIt is not used to evaluate directly either potable water or wastewater. However, It is oneof the most important parameters in natural surface water systems

Sources: ambient temperature (temperature of the surrounding atmosphere), industries discharge

waste heat

Impacts:


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- Biological activities increase when temperature increases. A 10OC increase in temperature issufficient to double the biological activity of organisms if the essential nutrients are available.

- Accelerated growth of algae often occurs in warm water and can become a problem when cellscluster into algae mats.

- Natural secretion of oils by the algae in the mats and decay products of dead algae cells can resulin taste and odor problems.

- The dead algae will also require oxygen in its decomposition which may result to a DO leveinsufficient to support higher-order species such as fishes

- Oxygen is more soluble in cold water than in warm water. This in turn affects the amount of DO inwater.

- Temperature also affects other physical properties of water. The viscosity increases withdecreasing temperature, the maximum density of water occurs at 4OC.

II. Chemical Water Quality Parameters1. Total Dissolved Solidsthe material remaining in the water after filtration and is left as residue upon

evaporation. It constitutes a part of total solids. Dissolved solids may be organic or inorganic

Sources: solvent action of water on solids, gases and liquids, decay products of vegetation or fromorganic chemicals and gases

Impacts:produces aesthetically displeasing color, tastes and odors, some maybe toxic and carcinogen

2. Alkalinityit is a measure of the ability of water to neutralize acidsSources: Dissolution of mineral substances in soil and atmosphere, phosphates originating from

detergents in wastewater, from fertilizers and insecticides from agricultural lands.

Impacts:alkalinity imparts bitter taste to water, reaction between alkalinity and other ions will produce

precipitates that can foul pipes and other water systems.

3. Hardnessconcentration of multivalent cations in solution. It is classified as carbonate and non-carbonate hardnessConcentration based on Calcium Carbonate concentration:


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Prevents dental cavities in children if the concentration is 1.0 ppm ( in drinking water)

Cause discoloration of teeth (mottling) if the concentration is > 2 ppm

Mottling is rare if the concentration is < 1.5 ppm

Can cause bone fluosis if the concentration is 5 ppm

Recommended limit in drinking water = 1.5 ppm

6. OrganicsBiodegradable Organics: dissolved from domestic or industrial wastewater discharges (starches, fats,

proteins, alcohols, acids, aldehydes, and esters)

Non-Biodegradable Organics/ Refractory organics: organics that are resistant to biological degradation

Examples: Tannic and lignic acids, cellulose and phenols degrade very slowly

Ring structured materials: benzene, detergent compounds ABS, pesticides, herbicides

Impacts: Health hazards (toxic and carcinogen), some cause frothing and foaming, increase turbidity

7. Nutrients: (Nitrogen and Phosphorus)Sources: Nitrogen containing compounds (proteins, animal wastes, fertilizers, wastewater discharges)

Phosphates in Municipal Waste water may come from detergents

Impacts:- NO3form of nitrogen may cause nitrate poisoning in babies (blue baby syndrome or

methemoglobinemia)

- Phosphates interfere with wastewater treatment- Nutrients in excessive amounts can cause Eutrophication of rivers.

Standards for Drinking WaterQuality Parameter Concentration

Color 15 color unit

Ph 6.5 -8.5

TDS 500 ppm

Chlorides 250 ppmFoaming agents 0.5 ppm

Sulfates 250 ppm

Zinc 5 ppm

Manganese 0.05 ppm

Iron 0.3 ppm

Copper 1 ppb

III. Biological Water Quality Parameters1. Waterborne diseases are those acquired by ingestion of pathogens not only in drinking water but alsofrom water that makes into a persons mouth from washing food, utensils, and hands

- Example: Giardia lamblia( a protozoa), Vibro Comma(bacteria)- Classification of Pathogens (causing water-borne diseases)

a) Bacteria: classified as cocci, bacilli, spirillab) Protozoa: an order of magnitude larger than bacteriac) Virusesd) Helminthsparasitic worms and other parasites


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6. Water-contact diseasesdo not require that individuals ingest the water- Schistosomiasis(bilharzias)It is a common water-contact disease in the world, affecting

approximately 200 million people. It is spread by free-swimming larva in the water called

Cercaria which are transported by snails.

7. Water Hygiene- Water also plays an indirect role in other diseases common in developing countries. Insects that

breed in water, or bite near water are responsible for the spread of malaria, affecting some 160

million people and killing 1 million each year. Yellow fever, sleeping sickness and river blindness

spread in the same way. Inadequate supplies of water for personal hygiene results in skin

Pathogens Disease Remarks

Bacteria

1. Escherichia coli(enteropathogenic)

Gastroenteritis Diarrhea

2. Leptospira Leptospirosis Jaundice, fever(Weils diseas3.

Salmonella typhi orSalmonella Typhosa Typhoid fever High fever, diarrhea, ulceratof the intestine

4. Salmonella Salmonellosis Food poisoning5. Vibrio Cholerae or Vibrio

Comma

Cholera Extremely heavy diarrhea,

dehydration

6. Shigella Shigellosis Bacillary dysentery7. Legionella pneumophila Legionellosis Acute respiratory illnessProtozoa

1. Giardia lamblia Giardiasis Mild to severe diarrhea, nauindigestion

2. Entamoeba histolytica Amebiasis Prolonged diarrhea withbleeding

3. Cryptosporidium parvum Cryptosporidiosis Diarrhea4. Balantidium coli Balantidiasis Diarrhea, dysenteryViruses

1. Adenovirus (31 types) Respiratory disease2. Endoteroviruses (67 types,

e.g. polio, Coxsackie viruses)

Gastroenteritis, heart anomalies,

meningitis

3. Hepatitis A Infectious hepatitis4. Norwalk agent Gastroenteritis5. Reovirus Gastroenteritis6. Rotavirus GastroenteritisHelminths

1. Ascaris lumbricoides Ascariasis Roundworm infestation2. Enterobius vericularis Enterobiasis Pinworm3. Taenia saginata Taeniasis Beef tapeworm4. Taenia solium Taeniasis Pork tapeworm5. Trichuris trichiura Trichuriasis Whipworm


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diseases such as scabies, leprosy, and yaws as well as eye diseases such as trachoma and

conjunctivitis.

-River Blindnesstiny intestinal worms that appears in a persons eye that in most cases would

cause blindness. These tiny intestinal worms are transported by flies. This disease was dominan

in Uganda Africa

Bacterial measures:1. Counting Colonies/ mlsample is placed in an agar sterile and incubated for 24-48 hours, afte

which darkspots are counted (indicating pathogen that have lysed)

2. MPNThe sample is placed in a lactose broth and allowed to ferment. The coliform produces gaand make the broth cloudy. The Bingham tube with was space is counted as positive. MPN stand

for Most Probable Number.

Additional Terms:1. Endemicrefers to a disease prevalent in and confined to a particular population2. Epidemicis an outbreak of an infectious disease spreading widely in a particular area3. Epidemiologyis the study of the causes of a disease spreading in a community4. Microbiologyis the study of microorganisms and their activities

IV. Radiological Water Quality Parameters- Excessive exposure to radioactive materials is harmful and unnecessary exposure should be

avoided (including drinking water). Radioactivity in public drinking water supplies is the 3r

category of contaminants regulated by the Safe Drinking water Act. Naturally occurring

Radioactive compounds include radon and radium 226 found in ground water. Strontium 90 and

tritium are also found in surface water resulting from atmospheric nuclear weapon testing

fallout.

-

Maximum Contaminant Level (MCL) for radium 226 + radium 228 = 5pci/L- MCL (for alpha particle activity) including radium 226 but excluding radon and uranium = 15

pci/L

- MCL (for beta particles and photon activity) 4 mrem/yr (annual dose to the whole body or anyparticular organ)

- The most significant radionuclides associated with drinking water is dissolved radon gas. Radongas is colorless, odorless and tasteless gas occurring naturally in ground water.

Categories of Drinking Water Standards1. Primary standards2. Secondary standards3. Radioactivity4. Microbial contaminants


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WATER PURIFICATION PROCESSES IN NATURAL SYSTEMS

Natural forms of pollutants have always been present in surface waters. Long before the dawn o

civilization, many impurities were washed from air, eroded from land surfaces, or leached from the soi

and ultimately found their way into the surface waters. With few exceptions, natural purification

processes were able to remove or otherwise render these materials harmless. Indeed, without these

self-cleaning processes, the water-dependent life on earth could not have developed as it did.

The self-purification mechanisms of natural water systems include physical, chemical and biologica

processes. The speed and completeness with which these processes occur depend on hydraulic

characteristics (volume, rate, turbulence of flow), physical characteristics of bottom and bank material

variations in sunlight and temperature, as well as the chemical nature of natural water. These are set by

nature and can seldom be altered.

I. Physical Processes1. Dilution

Wastewater disposal practices were based on the premise that the solution to pollution i

dilution. Dilution was considered the most economical means of wastewater disposal and wasconsidered good engineering practice. Although dilution is powerful adjunct to self-cleaning

mechanisms of surface waters, its success depends upon discharging relatively small quantities

of waste into large bodies of water. The dilution capacity of a stream can be calculated using the

principles of mass balance.

Concentration after mixing is calculated from:

2. Sedimentation and ResuspensionSuspended solids is one of the most common water pollutants and in suspension, solids increase

turbidity and reduce light penetration may restrict the photosynthetic activity of plants, inhibits

vision of aquatic animals, interfere with feeding of aquatic animals that obtain food fromfiltration and be abrasive to respiratory structures such as gills of fish.

Sedimentation is natures method of removing suspended particles from a watercourse and

most large solids will settle out readily in quiescent water. Particles in the colloidal size range

can stay in suspension for long periods of time though eventually most of these will also settle

out. This natural sedimentation is not without drawbacks.

Drawbacks of sedimentation:

- Anaerobic conditions are likely to develop in sediments and any organics trapped inthem will decompose, releasing soluble compounds into the stream above.

- Sediments deposit can also alter streambed by filling up the pore space and creatingunsuitable conditions for the reproduction of many aquatic organisms.

- It can also alter its course or hamper navigation activities and reduce reservoir storagecapabilities and silt in harbors and increase flooding due to channel fill-in.

Resuspension of solids is common in times of flooding or heavy runoff. Increased turbulence ay

resuspend solids formerly deposited along normally quiescent areas of stream and carry them

for considerable distances downstream and eventually they will settle again.


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3. FiltrationLarge bits of debris lodge on reeds or stones as they move along streambeds and they remain

caught until high waters wash them into mainstream again. Small bits of organic matters and

inorganic clays and other sediments may be filtered out by pebbles or rocks along the

streambed. As water percolates from the surface downward into groundwater aquifers

filtration of a much more sophisticated type occurs. If the soil layers are deep and fine enough

removal of suspended material is essentially complete by the time water enters the aquifer.

4. Gas TransferThe transfer of gases into and out of water is an important part of the natural purification

process. The replenishment of oxygen lost to bacterial degradation of organic waste is

accomplished by the transfer of oxygen from the air into the water. Conversely, gases evolved in

the water by chemical and biological processes may be transferred for the water to the

atmosphere. Gas transfer is affected by solubility (extent to which gas is soluble in the water

and transfer rate ( rate at which dissolution or release occurs).

5. Heat TransferBodies of water lose and gain heat much more slowly than do land or air masses and under moscircumstances, water temperature is fairly constant and changes gradually with the seasons

Meteorological variables and other factors such as channel characteristics (depth, width, surface

area), channel volume, etc. affect the rate of heat transfer in bodies of water. For streams

heated by solar radiation over several miles of heat-load area, cooling begins only in shaded

areas or at night and may proceed much more slowly than cooling in streams which receive

their heat load in one discharge

II. Chemical Processes6. Chemical Conversions:

Oxidation-reduction, dissolution-precipitation and other chemical conversions mayalternately aid or obstruct natural purification processes of natural water systemStrictly speaking, Oxidation-reduction conversions that play a part in self-purification of

watercourses are biochemically mediated.

Certain minerals pass into and out of solution and natural chemical conversions thatmay take place in water can change theses materials into a form that is soluble and

useable by various aquatic organisms.

Examples are Iron, Manganese, copper, zinc, molybdenum and cobalt which aremicronutrients needed by microorganisms for biochemical processes.

Nutrients (Nitrogen and Phosphorous) are present in watercourses and when ferric ionis also present the following reaction will occur:

The precipitate is insoluble ferric phosphate and settles to the bottom. Chemical conversions that take place in streams and lakes can help to stabilize the pH of

those bodies of water. Limestone and other forms of CaCO3 dissolve readily in wate

containing CO2. Carbonic acid may for and dissociates thereby producing hydrogen ions

The hydrogen ions thus formed react with slightly soluble calcium carbonate to yield


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highly soluble calcium and more bicarbonate ions. The bicarbonate ions act as buffer to

protect a stream fro pH fluctuations that can be harmful to aquatic systems.

III. Biological Process7. Metabolic Processes (Biochemical processes)

Many chemical reactions involved in the self-purification process are biologicallymediated. In case of biodegradable organics and other nutrients, the activation energy

can be supplied by microorganisms that utilize these materials for food and energy.

The process by which living organisms assimilate and use food for subsistence, growthand reproduction is called metabolism. The metabolic processes and the organism

involved are a vital part of the self-purification process of natural water systems.

Catabolismprovides the energy for synthesis of new cells as well as for maintenance forother cell functions.

Anabolismprovides the material necessary for cell growth Microorganisms that play an important role in natural water-system

1. Bacteria- Primary decomposers of organic material. Autotrophs derive both

energy and material from inorganic sources while heterotrophs obtain

both energy and material from organic compounds. Phototrophs are

those bacteria which utilize sunlight for an energy source and inorganic

substances for material source.

2. Protozoa- Protozoa are single-cell organisms that reproduce by binary fissionProtozoa re voracious consumers of organic material and are importan

members of the aquatic community

3. Algae- These are autotrophic, photosynthetic organisms which metabolize the

waste product of heterotrophic bacteria while obtaining energy fo

sunlight

4. Other organismsrotifers and Crustacea, Sludge worms

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engg.500 notes.docx