M. Shah Alam Khan Professor Institute of Water and Flood Management, Bangladesh University of...

M. Shah Alam KhanM. Shah Alam Khan

ProfessorProfessorInstitute of Water and Flood Management,Institute of Water and Flood Management,

Bangladesh University of Engineering and TechnologyBangladesh University of Engineering and Technology

Hydro-ecological InvestigationHydro-ecological Investigation

WFM 6209 : Interdisciplinary Field Research Methodology

in Water Management

Hydro-ecological InvestigationHydro-ecological Investigation ObjectivesObjectives

Learn application of hydro-ecological Learn application of hydro-ecological investigation techniques and analysis methods investigation techniques and analysis methods that may be required for interdisciplinary field that may be required for interdisciplinary field research.research.

Learn how to interpret the results of analysis in Learn how to interpret the results of analysis in terms of the biophysical environment.terms of the biophysical environment.

Hydro-ecological InvestigationHydro-ecological Investigation

Water quantity measurement and analysis

Physico-chemical analysis of water and soil

Ecological Assessment

Agro-ecological Assessment

RS and GIS Applications

Environmental DescriptorsEnvironmental Descriptors

Physical-Chemical EnvironmentPhysical-Chemical Environment Biological EnvironmentBiological Environment Socioeconomic EnvironmentSocioeconomic Environment Political EnvironmentPolitical Environment Cultural EnvironmentCultural Environment … …… …

Environmental DescriptorsEnvironmental Descriptors

Physical-Chemical EnvironmentPhysical-Chemical Environment

Physical-Chemical EnvironmentPhysical-Chemical Environment

Water qualityWater quality- - Physical parametersPhysical parameters (suspended solids, turbidity, color, taste and (suspended solids, turbidity, color, taste and odor, temperature, etc.)odor, temperature, etc.)- - Chemical parametersChemical parameters (pH, alkalinity, hardness, fluoride, metals, (pH, alkalinity, hardness, fluoride, metals, organics, nutrients, etc.)organics, nutrients, etc.)- - Biological parametersBiological parameters (pathogens, pathogen indicators) (pathogens, pathogen indicators)

Surface water resourcesSurface water resources (flow, volume, depth, in-stream storage, (flow, volume, depth, in-stream storage, etc.) etc.)

Groundwater resourcesGroundwater resources (levels, recharge, quantity and quality) (levels, recharge, quantity and quality) SoilsSoils Land type, land useLand type, land use GeologyGeology TopographyTopography AgricultureAgriculture Climatology Climatology (precipitation, evapotranspiration, etc.)(precipitation, evapotranspiration, etc.) Air qualityAir quality Noise pollutionNoise pollution

Hydro-ecological Investigation : KaliakoirHydro-ecological Investigation : Kaliakoir

Measurement / Secondary dataMeasurement / Secondary data Water Quantity:Water Quantity:

- Flow rate in - Flow rate in khalskhals, river, river- Discharge (flow rate) from industries- Discharge (flow rate) from industries- GW withdrawn by industries- GW withdrawn by industries- GW levels- GW levels- WL in - WL in beelsbeels

Water Quality:Water Quality:- Color, Solids, Temperature, pH, Hardness, Metals, DO, - Color, Solids, Temperature, pH, Hardness, Metals, DO, BOD, COD, NutrientsBOD, COD, Nutrients

Ecology:Ecology:- Fish: Population (catch), Composition (diversity)- Fish: Population (catch), Composition (diversity)- Other flora/fauna- Other flora/fauna

RS and GIS Applications:RS and GIS Applications:- Land type, Land use, Drainage network, Resource maps- Land type, Land use, Drainage network, Resource maps

AnalysisAnalysis Impact of GW withdrawal by industriesImpact of GW withdrawal by industries Pollutant mass balance: impact of industrial dischargePollutant mass balance: impact of industrial discharge Historical change in WQ (surface and groundwater)Historical change in WQ (surface and groundwater) Historical change in fish catch and diversityHistorical change in fish catch and diversity Historical change in land use, water bodiesHistorical change in land use, water bodies

Hydro-ecological Investigation : KaliakoirHydro-ecological Investigation : Kaliakoir

Hydrologic CycleHydrologic Cycle

• Interference at one stage can cause serious repercussions at some other stage of hydrologic cycle

• It is important to understand the relationship among the components at different stages of the cycle

Hydrologic CycleHydrologic Cycle The Hydrologic Cycle and Water Quality

Water in nature is most nearly pure in its evaporation state.

Condensation of water around particles acquires impurities.

Additional impurities are acquired as the liquid water travels further through the hydrologic cycle.

Human activities contribute further impurities through:

- industrial and domestic wastes

- agricultural chemicals.

Impurities in water may be in both suspended and dissolved forms.

- Suspended materials are larger than molecular size.

- Dissolved materials consist of molecules or ions that are held by the molecular structure of water.

- Colloids (10-3 to 10-6 mm) are very small suspended particles, but often exhibit many characteristics of the dissolved substances.

Water PollutionWater Pollution

Presence of impurities in water in such quantity and of such nature as to impair the use of water for a stated purpose.

‘Pollution’ is a relative term – depends on intended use.

‘Water Quality Parameters’ qualitatively reflect the impact of impurities on selected water uses.

Analytical procedures quantitatively measure the parameters that represent the physical, chemical and biological characteristics of water.

Water Quality: Measurement and AnalysisWater Quality: Measurement and Analysis

Physical Parameters:Physical Parameters:1. Color1. Color2. Taste and Odor2. Taste and Odor3. Solids (Suspended, 3. Solids (Suspended,

Total)Total)4. Turbidity4. Turbidity5. Temperature5. Temperature

Chemical Parameters:1. pH2. Total Dissolved Solids3. Alkalinity4. Salinity5. Hardness6. Fluoride7. Metals8. Organics (DO, BOD)9. COD10. Nutrients

- Source, Impact and Measurement of each parameter- Consult Standards and Guidelines for specific use

ColorColorSources:Sources: Domestic and industrial wastes, natural decay of organic materials.Domestic and industrial wastes, natural decay of organic materials. Organic debris such as leaves, weeds or wood.Organic debris such as leaves, weeds or wood. Industrial wastes from textile and dyeing operations, pulp and paper Industrial wastes from textile and dyeing operations, pulp and paper

production, food processing, chemical production, and mining, refining production, food processing, chemical production, and mining, refining and slaughterhouse operations.and slaughterhouse operations.

Iron-oxides cause reddish color, and manganese oxides cause brown Iron-oxides cause reddish color, and manganese oxides cause brown or brackish water.or brackish water.

Water Quality: Measurement and Analysis

Impacts: • Color affects acceptability of water as both domestic and industrial

product.• Colored water is not aesthetically acceptable to the general public.• Highly colored water is unsuitable for laundering, dyeing,

papermaking, beverage manufacturing, dairy production and other food processing, and textile and plastic production.

Water Quality: Measurement and AnalysisPhysical Parameters

ColorColorMeasurement:Measurement: Often measured by comparison with standardized colored materials.Often measured by comparison with standardized colored materials. Color-comparison tubes containing a series of standards (different Color-comparison tubes containing a series of standards (different

colors) may be used for direct comparison with the water sample. colors) may be used for direct comparison with the water sample. Results are expressed as True Color Units (TCU) where one unit is Results are expressed as True Color Units (TCU) where one unit is

equivalent to the color produced by 1 mg/L of platinum in the form of equivalent to the color produced by 1 mg/L of platinum in the form of chlorplatinate ions.chlorplatinate ions.

Special spectrophotometric techniques are normally used for colored Special spectrophotometric techniques are normally used for colored water originating from industrial waste effluents.water originating from industrial waste effluents.

Calibrated colored disks are used in field work.Calibrated colored disks are used in field work.


Taste and OdorTaste and OdorSources:Sources: Many natural or artificial substances impart taste and odor including:Many natural or artificial substances impart taste and odor including:

- Minerals, metals and salts from the soil- Minerals, metals and salts from the soil- End products from biological reactions- End products from biological reactions- Constituents of wastewater- Constituents of wastewater

Inorganic substances are more likely to produce tastes Inorganic substances are more likely to produce tastes unaccompaniedunaccompanied by by odors.odors.

Organic materials are likely to produce Organic materials are likely to produce bothboth taste and odor. taste and odor. Alkaline materials impart bitter taste; metallic salts may give a salty or bitter Alkaline materials impart bitter taste; metallic salts may give a salty or bitter

taste.taste. Petroleum-based products are the primary taste- and odor-producing organic Petroleum-based products are the primary taste- and odor-producing organic

chemicals.chemicals. Biological decomposition of organics may also result in taste- and odor-Biological decomposition of organics may also result in taste- and odor-

producing liquids and gases. (e.g. ‘rotten egg’ taste and odor of sulfur).producing liquids and gases. (e.g. ‘rotten egg’ taste and odor of sulfur). Certain species of algae secrete taste- and odor-producing oily substance.Certain species of algae secrete taste- and odor-producing oily substance. Sometimes the combination of two or more substances, neither of which Sometimes the combination of two or more substances, neither of which

would individually produce taste or odor, may cause taste and odor problems.would individually produce taste or odor, may cause taste and odor problems.


Taste and OdorTaste and OdorImpacts:Impacts: Displeasing to the consumers for obvious reasons.Displeasing to the consumers for obvious reasons. Some odor-producing organic substances are found to be Some odor-producing organic substances are found to be

carcinogenic.carcinogenic.

Measurement:Measurement:

Quantitative tests sometimes employ human senses of taste and smell. Quantitative tests sometimes employ human senses of taste and smell. The Threshold Odor Number (TON) test uses varying volumes of the The Threshold Odor Number (TON) test uses varying volumes of the sample diluted to 200mL with distilled water. 5 to 10 people determine sample diluted to 200mL with distilled water. 5 to 10 people determine the mixture in which the smell is just barely detectable. The TON is the mixture in which the smell is just barely detectable. The TON is given by,given by,

A

BATON

where A = the volume of odorous water (mL), and B = the volume (mL) of odor-free water required to produce a 200-mL mixture.


SolidsSolidsSources:Sources: May consist of May consist of inorganic inorganic or or organicorganic particles, or particles, or immiscibleimmiscible liquids: liquids:

- Inorganic solids: clay, silt or other soil constituents;- Inorganic solids: clay, silt or other soil constituents;- Organic solids: plant fibers and biological solids (algal cells, bacteria, etc.);- Organic solids: plant fibers and biological solids (algal cells, bacteria, etc.);- Immiscible liquids: oils and greases.- Immiscible liquids: oils and greases.

Common constituents of surface waters.Common constituents of surface waters. Often result from erosive action of water over surfaces.Often result from erosive action of water over surfaces. Very rarely found in groundwater because of the natural filtering capacity of soil.Very rarely found in groundwater because of the natural filtering capacity of soil. May also result from human use:May also result from human use:

- Domestic wastewater usually contains large quantities of organic solids;- Domestic wastewater usually contains large quantities of organic solids;- Industrial wastewater contains both inorganic and organic solids.- Industrial wastewater contains both inorganic and organic solids.

Impacts:Impacts: Aesthetically displeasing;Aesthetically displeasing; Provides Provides adsorption sites (surfaces)adsorption sites (surfaces) for chemical and biological agents; for chemical and biological agents; Biological degradation of organic solids may produce objectionable by-products;Biological degradation of organic solids may produce objectionable by-products; Biologically active solids may include disease-causing organisms and toxin-Biologically active solids may include disease-causing organisms and toxin-

producing algae.producing algae.

Measurement:Measurement: Total Solids TestTotal Solids Test Suspended Solids TestSuspended Solids Test


SolidsSolids

Measurement:Measurement: Total Solids TestTotal Solids Test

- measures all solids (suspended and dissolved, inorganic and - measures all solids (suspended and dissolved, inorganic and organic):organic):- Water sample is heated to a temperature slightly above boiling - Water sample is heated to a temperature slightly above boiling (104(104ooC) [drives off liquids and the water adsorbed to the particle C) [drives off liquids and the water adsorbed to the particle surfaces; a temperature of about 180oC is required to evaporate the surfaces; a temperature of about 180oC is required to evaporate the occluded water];occluded water];- The residue is weighed and expressed as milligrams per liter (mg/L) - The residue is weighed and expressed as milligrams per liter (mg/L) [‘dry-mass’ weight of residue (in mg) per liter volume of sample]. [‘dry-mass’ weight of residue (in mg) per liter volume of sample].

Suspended Solids TestSuspended Solids Test

- measures the mass of residue retained on a filter (paper).- measures the mass of residue retained on a filter (paper).

- The water sample is filtered, and the filter and residue is dried to a - The water sample is filtered, and the filter and residue is dried to a constant weight at 104constant weight at 104ooC (+/- 1C (+/- 1ooC).C).

- The difference between weights of the filter before and after filtration - The difference between weights of the filter before and after filtration gives the weight of residue (suspended solids). gives the weight of residue (suspended solids).

- Residue (dry-mass) is expressed as mg/L.- Residue (dry-mass) is expressed as mg/L.


SolidsSolids


The Dissolved Solids passing through the filters is the difference between the total-solids and suspended-solids contents of the sample.

Figure: Filtration apparatus.

SolidsSolids


NotesNotes::

1. Some solids (e.g. colloids) may pass through the filter and add to the dissolved-solids contents (filterable residues) while some dissolved solids may adsorb to the filter material and add to the suspended-solids content (nonfilterable residues). [extent depends on the size and nature of the solids, and the pore opening and nature of the filter material].

2. Organic content of both total and suspended solids can be removed by firing (burning in oven) the residues at 600oC for 1 hour. [organic fraction converts into carbon dioxide, water vapor and other gases; a filter made of glass fiber or other high-temperature resistant material is used].

Use:Use:

An important parameter of wastewater:

• to indicate the quality of influent and effluent.

• to monitor treatment processes.

SolidsSolids


TurbidityTurbidity- A measure of the extent to which light is either absorbed or scattered by suspended - A measure of the extent to which light is either absorbed or scattered by suspended

materials in water.materials in water.- Turbidity tests are commonly performed on natural water bodies and potable (drinkable) - Turbidity tests are commonly performed on natural water bodies and potable (drinkable)

water supplies.water supplies.- Turbidity does not directly quantify the suspended solids.- Turbidity does not directly quantify the suspended solids.

Sources: • Erosion of colloidal materials such as clay, silt and metal oxides from the soil.• Vegetable fibers and microorganisms.• Domestic and industrial wastewaters (soaps, detergents and emulsifying agents produce

stable colloids).• Discharges of wastewaters may increase the turbidity of natural water bodies.

Impacts: • Aesthetically displeasing opaqueness (‘milky’ coloration).• Turbidity-producing colloidal materials provide adsorption sites for taste- and odor-

producing chemicals, and harmful organisms.• Disinfection of turbid waters is difficult because of the adsorptive characteristics of the

colloids and since the solids may partially shield the organisms.• Turbid waters interfere with light penetration and photosynthetic reactions in streams

and lakes.• Turbidity-causing fine particles may deposit on porous streambed and adversely affect

the flora and fauna.• Suspended materials absorb heat from sunlight and raise the water temperature.


TurbidityTurbidityMeasurement:


TemperatureTemperature- Influences to a large extent the biological species and their activity rates in - Influences to a large extent the biological species and their activity rates in

water.water.- Affects most chemical reactions and solubility of gases in natural water - Affects most chemical reactions and solubility of gases in natural water

systems.systems.

Sources:Sources: The natural-water temperature responds to the ambient (surrounding) The natural-water temperature responds to the ambient (surrounding)

temperature. Generally, shallow water bodies are more affected by ambient temperature. Generally, shallow water bodies are more affected by ambient temperature.temperature.

The warm or heated water discharged from many industries may dramatically The warm or heated water discharged from many industries may dramatically (but locally) elevate the temperature of receiving streams.(but locally) elevate the temperature of receiving streams.

Impacts:Impacts: Cooler water usually allows wider diversity of biological species.Cooler water usually allows wider diversity of biological species. Accelerated algal growth occurs in warm water, and may cause problems by Accelerated algal growth occurs in warm water, and may cause problems by

oil secretion, thick ‘algal mat’ (cells joined together) and decay products of the oil secretion, thick ‘algal mat’ (cells joined together) and decay products of the dead algae cells.dead algae cells.

Higher-order species, e.g. fish, are drastically affected by change in Higher-order species, e.g. fish, are drastically affected by change in temperature, and by change in dissolved oxygen (a function of temperature).temperature, and by change in dissolved oxygen (a function of temperature).


TemperatureTemperature

Impacts:Impacts: More chemical reactions involving dissolution of solids are accelerated by More chemical reactions involving dissolution of solids are accelerated by

increased temperatures.increased temperatures. Increase in temperature affects physical properties of water including: Increase in temperature affects physical properties of water including:

Viscosity (decrease), and density (maxm at 4Viscosity (decrease), and density (maxm at 4ooC).C). Temperature and density affect the growth and stratification of planktonic Temperature and density affect the growth and stratification of planktonic

microorganisms in natural water systems.microorganisms in natural water systems.


Measurement:By thermometers, thermocouples and transducers.

pHpH

Impacts:Impacts: If pH < 5.5, the water may be If pH < 5.5, the water may be

too acidic for fish to survive in, too acidic for fish to survive in, while water with a pH > 8.6 while water with a pH > 8.6 may be too basic.may be too basic.

A change in pH can also affect A change in pH can also affect aquatic life indirectly by altering aquatic life indirectly by altering other aspects of water other aspects of water chemistry. For example, low chemistry. For example, low pH levels can increase the pH levels can increase the solubility of certain heavy solubility of certain heavy metals.metals.

Water Quality: Measurement and AnalysisChemical Parameters

pH = - log [H+]pH = - log [H+](negative logarithm of hydrogen ion concentration)(negative logarithm of hydrogen ion concentration)

pH = 7 => ‘neutral’pH = 7 => ‘neutral’pH < 7 => ‘acidic’pH < 7 => ‘acidic’pH > 7 => ‘basic/alkaline’pH > 7 => ‘basic/alkaline’

AlkalinityAlkalinityThe quantity of ions in water that will react to neutralize hydrogen ions. The quantity of ions in water that will react to neutralize hydrogen ions.

Alkalinity is thus a measure of the ability of water to neutralize acids.Alkalinity is thus a measure of the ability of water to neutralize acids.

Sources:Sources: Commonly found in natural water systems: carbonate (COCommonly found in natural water systems: carbonate (CO33

2-2-), ), bicarbonate (HCObicarbonate (HCO33

--), hydroxide (OH), hydroxide (OH--), silicate (HSiO), silicate (HSiO33--), bromate ), bromate

(H(H22BOBO33--), phosphates (HPO), phosphates (HPO44

2-2-, H, H22POPO44--), sulfide (HS), sulfide (HS--), and ammonia ), and ammonia

(NH(NH3300). These result from dissolution of mineral substances in soil and ). These result from dissolution of mineral substances in soil and

atmosphere.atmosphere. Phosphates may also originate from detergents in wastewaters and Phosphates may also originate from detergents in wastewaters and

from fertilizers and insecticides from agricultural land. Hydrogen from fertilizers and insecticides from agricultural land. Hydrogen sulfide and ammonia may be produced from microbial decomposition sulfide and ammonia may be produced from microbial decomposition of organic material.of organic material.

Most common constituents of alkalinity: COMost common constituents of alkalinity: CO332-2-, HCO, HCO33

--, and OH, and OH--. In . In addition to their mineral origin these constituents may originate from addition to their mineral origin these constituents may originate from carbon dioxide (COcarbon dioxide (CO22) and microbial decomposition of organic material.) and microbial decomposition of organic material.

The relative quantities of alkalinity species are pH dependent.The relative quantities of alkalinity species are pH dependent. Figure shows variation in concentrations of alkalinity species with pH.Figure shows variation in concentrations of alkalinity species with pH.


AlkalinityAlkalinity


AlkalinityAlkalinityImpacts:Impacts: In large quantities, alkalinity imparts a bitter taste to water.In large quantities, alkalinity imparts a bitter taste to water. A major problem with alkaline water is the reaction that may occur A major problem with alkaline water is the reaction that may occur

between alkalinity species and certain cations. Resultant precipitates between alkalinity species and certain cations. Resultant precipitates may damage pipes and other appurtenances. may damage pipes and other appurtenances.


Measurement :Measurement : Alkalinity is measured by Alkalinity is measured by titratingtitrating the water with an acid and the water with an acid and

determining the hydrogen equivalent. Alkalinity is usually expressed determining the hydrogen equivalent. Alkalinity is usually expressed as mg/L of CaCOas mg/L of CaCO33. If 0.02 . If 0.02 NN H H22SOSO44 (0.02 ‘Normal’ sulfuric acid; (0.02 ‘Normal’ sulfuric acid; ‘Normal’ indicates strength of acid) is used for titration, then 1 mL of ‘Normal’ indicates strength of acid) is used for titration, then 1 mL of the acid will neutralize 1 mg of alkalinity as CaCOthe acid will neutralize 1 mg of alkalinity as CaCO33..

The volumes of acid required to reach the The volumes of acid required to reach the endpointsendpoints of titration (pH = of titration (pH = 8.3 and pH = 4.5) determine the different species of alkalinity present. 8.3 and pH = 4.5) determine the different species of alkalinity present. Endpoints are indicated by change of color of certain chemicals called Endpoints are indicated by change of color of certain chemicals called indicatorsindicators that are added before titration. that are added before titration.

Use:Use: Alkalinity indicates the Alkalinity indicates the buffering capacitybuffering capacity (acid neutralizing capacity) (acid neutralizing capacity)

of natural waters.of natural waters. Also used as process control variable in water and wastewater Also used as process control variable in water and wastewater

treatment.treatment.

HardnessHardness Concentration of Concentration of multivalentmultivalent metallic cations in solution. In metallic cations in solution. In supersaturated supersaturated

condition, the hardness cations react with anions to form a solid precipitate.condition, the hardness cations react with anions to form a solid precipitate. Hardness can be classified as Hardness can be classified as carbonatecarbonate hardnesshardness and and noncarbonatenoncarbonate

hardnesshardness depending on the anions they are associated with. Hardness depending on the anions they are associated with. Hardness equivalent to the alkalinity is called carbonate hardness. Any remaining equivalent to the alkalinity is called carbonate hardness. Any remaining hardness is called noncarbonate hardness. Carbonate hardness is sensitive hardness is called noncarbonate hardness. Carbonate hardness is sensitive to heat and precipitates readily at high temperatures. to heat and precipitates readily at high temperatures.

Sources:Sources: Calcium and magnesium constitute almost all hardness in natural waters.Calcium and magnesium constitute almost all hardness in natural waters. Others include iron and manganese in their reduced forms (FeOthers include iron and manganese in their reduced forms (Fe2+2+, Mn, Mn2+2+), ),

strontium (Srstrontium (Sr2+2+), and aluminum (Al), and aluminum (Al3+3+). ).


Impacts:Impacts:Sodium-based soaps react with the hardness cations to form a Sodium-based soaps react with the hardness cations to form a precipitate, thereby losing their surfactant properties. Soap precipitate, thereby losing their surfactant properties. Soap consumption by hard water incurs economic loss to the water user. consumption by hard water incurs economic loss to the water user. Precipitates formed by hardness and soap adhere to appurtenance Precipitates formed by hardness and soap adhere to appurtenance surfaces and may stain clothing and utensils. Use of hard water may surfaces and may stain clothing and utensils. Use of hard water may result in rough, uncomfortable skin. Certain soaps do not react with result in rough, uncomfortable skin. Certain soaps do not react with hardness. hardness.

FlourideFlouride Generally found in surface waters; rarely found in groundwater.Generally found in surface waters; rarely found in groundwater. Toxic to human and other animals in large quantities; small quantities Toxic to human and other animals in large quantities; small quantities

may be beneficial: approx. 1 mg/L in drinking water may help prevent may be beneficial: approx. 1 mg/L in drinking water may help prevent dental cavity, and form decay resistant teeth.dental cavity, and form decay resistant teeth.

Excessive fluoride in drinking water causes discoloration of teeth Excessive fluoride in drinking water causes discoloration of teeth ((mottlingmottling) and bone formation abnormalities. ) and bone formation abnormalities.


MetalsMetals

All metals are soluble to some extent in water.All metals are soluble to some extent in water. Metals that are harmful in relatively small amounts are considered Metals that are harmful in relatively small amounts are considered

toxic.toxic. Metals in natural waters originate from dissolution of natural deposits, Metals in natural waters originate from dissolution of natural deposits,

and discharges of domestic, industrial or agricultural wastewaters.and discharges of domestic, industrial or agricultural wastewaters. Measurement usually made by Measurement usually made by atomic absorption spectrophotometeratomic absorption spectrophotometer

(AAS).(AAS).


MetalsMetals


Nontoxic Metals:Nontoxic Metals: Commonly found in water; include sodium, iron, manganese, Commonly found in water; include sodium, iron, manganese,

aluminum, copper and zinc. aluminum, copper and zinc. Sodium is the most common nontoxic metal and highly reactive to Sodium is the most common nontoxic metal and highly reactive to

other elements; excessive concentrations of sodium salts impart a other elements; excessive concentrations of sodium salts impart a bitter taste, and are hazardous to cardiac and kidney patients; also bitter taste, and are hazardous to cardiac and kidney patients; also corrosive to metal surfaces and toxic to plants.corrosive to metal surfaces and toxic to plants.

Iron and manganese frequently occur together in natural waters and Iron and manganese frequently occur together in natural waters and present no health hazard. May produce color problems and bacterial present no health hazard. May produce color problems and bacterial growth causing taste and odor.growth causing taste and odor.

Significant quantities of iron are usually found in systems devoid of Significant quantities of iron are usually found in systems devoid of oxygen such as groundwater and bottom layers of stratified lakes.oxygen such as groundwater and bottom layers of stratified lakes.

Copper and zinc, if both present, may be toxic to many biological Copper and zinc, if both present, may be toxic to many biological species. species.

MetalsMetals


Toxic Metals:Toxic Metals: Harmful to human and other organisms in small quantities.Harmful to human and other organisms in small quantities. Toxic metals that may be dissolved in water include arsenic, barium, Toxic metals that may be dissolved in water include arsenic, barium,

cadmium, chromium, lead, mercury and silver. Arsenic, cadmium, cadmium, chromium, lead, mercury and silver. Arsenic, cadmium, lead and mercury are particularly hazardous.lead and mercury are particularly hazardous.

These metals are concentrated by the These metals are concentrated by the food chainfood chain.. Toxic metals usually originate from natural, industrial, or agricultural Toxic metals usually originate from natural, industrial, or agricultural

sources.sources.

OrganicsOrganics


Many organics in natural water systems originate from natural sources and are Many organics in natural water systems originate from natural sources and are soluble in water. May consist of the decay products of organic solids, or result soluble in water. May consist of the decay products of organic solids, or result from wastewater and agricultural discharges. Harmful to human and other from wastewater and agricultural discharges. Harmful to human and other organisms in small quantities.organisms in small quantities.

Biodegradable Organics: Biodegradable Organics: Organics that are used up by microorganisms for food; usually consist of Organics that are used up by microorganisms for food; usually consist of

starches, fats, proteins, alcohols, aldehydes and esters.starches, fats, proteins, alcohols, aldehydes and esters. Microbial decomposition of dissolved organics normally takes place Microbial decomposition of dissolved organics normally takes place

accompanied by accompanied by oxidationoxidation (addition of oxygen or reduction of hydrogen), or by (addition of oxygen or reduction of hydrogen), or by reductionreduction (addition of hydrogen or reduction of oxygen). (addition of hydrogen or reduction of oxygen).

The decomposition may occur in The decomposition may occur in aerobicaerobic (oxygen-present) or (oxygen-present) or anaerobicanaerobic (oxygen-absent) environment.(oxygen-absent) environment.

Anaerobic decomposition results in unstable and objectionable end products.Anaerobic decomposition results in unstable and objectionable end products. When oxygen utilization occurs more rapidly than oxygen is replenished, When oxygen utilization occurs more rapidly than oxygen is replenished,

anaerobic conditions occur that severely affect the ecology of the system.anaerobic conditions occur that severely affect the ecology of the system. The amount of oxygen consumed during microbial utilization of organics is The amount of oxygen consumed during microbial utilization of organics is

called called Biochemical Oxygen DemandBiochemical Oxygen Demand (BOD). (BOD).

OrganicsOrganics


BOD is measured by determining the oxygen consumed from a sample BOD is measured by determining the oxygen consumed from a sample placed in an air-tight container and kept in a controlled environment for placed in an air-tight container and kept in a controlled environment for a specified period of time. In the standard test, a a specified period of time. In the standard test, a 300-mL 300-mL BOD bottleBOD bottle is is used and the sample is used and the sample is incubatedincubated at 20 at 20ooCC for 5 (sometimes 7) days. for 5 (sometimes 7) days. Light is excluded from the incubator to prevent algal growth. The Light is excluded from the incubator to prevent algal growth. The saturation concentration of oxygen in water at 20saturation concentration of oxygen in water at 20ooC is approx. 9 mg/L. C is approx. 9 mg/L. DilutionDilution or or seedingseeding of the sample may be required depending on the of the sample may be required depending on the anticipated BOD of the sample.anticipated BOD of the sample.

The BOD of a diluted sample is calculated by,The BOD of a diluted sample is calculated by,

where DOwhere DOi i and DOand DOf f are the initial and final dissolved oxygen are the initial and final dissolved oxygen

concentrations, and P is the decimal fraction of the sample in the BOD concentrations, and P is the decimal fraction of the sample in the BOD bottle. P = 1.0 for no dilution.bottle. P = 1.0 for no dilution.

Presence of toxic materials in water will invalidate the BOD results. Presence of toxic materials in water will invalidate the BOD results.

P

DODOBOD fi

OrganicsOrganics


Table 2.5 shows ranges of BOD covered by various dilutions, assuming an initial Table 2.5 shows ranges of BOD covered by various dilutions, assuming an initial dissolved-oxygen concentration of 9 mg/L, and for a 2 to 7 mg/L consumption of dissolved-oxygen concentration of 9 mg/L, and for a 2 to 7 mg/L consumption of oxygen.oxygen.

OrganicsOrganics


OrganicsOrganics

ktot eLL


The BOD for any time period can be determined mathematically by,The BOD for any time period can be determined mathematically by,

where Lwhere Lt t = the oxygen equivalent of the organics at time t, L= the oxygen equivalent of the organics at time t, Loo = oxygen = oxygen

equivalent of the organics at time zero, and k = a reaction constant. Units of L equivalent of the organics at time zero, and k = a reaction constant. Units of L and k are mg/L and dayand k are mg/L and day-1-1, respectively. Figure shows the variation of BOD and , respectively. Figure shows the variation of BOD and oxygen-equivalent of organics with time. oxygen-equivalent of organics with time.

OrganicsOrganics


Non-Biodegradable Organics: Non-Biodegradable Organics: Some organic materials (tannic and lignic acids, cellulose, phenols, Some organic materials (tannic and lignic acids, cellulose, phenols,

etc.) are resistant to biological degradation.etc.) are resistant to biological degradation. Benzenes and molecules having strong bonds are nonbiodegradable.Benzenes and molecules having strong bonds are nonbiodegradable. Many insecticides and herbicides are nonbiodegradable, and may be Many insecticides and herbicides are nonbiodegradable, and may be

extremely harmful to human and other species.extremely harmful to human and other species. Nonbiodegradable organics may be measured by the Nonbiodegradable organics may be measured by the Chemical Chemical

Oxygen Demand (COD)Oxygen Demand (COD) and and Total Organic Carbon (TOC)Total Organic Carbon (TOC) analyses. analyses. (BOD must be subtracted)(BOD must be subtracted)

NutrientsNutrients


Nutrients are elements essential to the growth and reproduction of Nutrients are elements essential to the growth and reproduction of plants and animals. plants and animals.

A wide variety of minerals and trace element may be classified as A wide variety of minerals and trace element may be classified as nutrients.nutrients.

Carbon, nitrogen and phosphorus are required in most abundance by Carbon, nitrogen and phosphorus are required in most abundance by the aquatic species.the aquatic species.

PathogensPathogens

Water Quality: Measurement and AnalysisBiological Parameters

Communicable diseases are caused by Communicable diseases are caused by bacteriabacteria, , virusesviruses, , protozoaprotozoa or or helminthshelminths (parasitic worms). Bacterial diseases include typhoid, (parasitic worms). Bacterial diseases include typhoid, paratyphoid, salmonellosis, shigellosis, bacillary dysentery, and paratyphoid, salmonellosis, shigellosis, bacillary dysentery, and cholera. Viral diseases include hepatitis, poliomyelitis, and some cholera. Viral diseases include hepatitis, poliomyelitis, and some varieties of gastroenteritis. Protozoa such as varieties of gastroenteritis. Protozoa such as GiardiaGiardia and and CryptosporidiumCryptosporidium may produce gastroenteritis. Certain fungi such as may produce gastroenteritis. Certain fungi such as AspergillusAspergillus also produce diseases in human bodies. also produce diseases in human bodies.

Pathogen IndicatorsPathogen Indicators

Water Quality: Measurement and AnalysisBiological Parameters

Testing for all possible microorganisms is infeasible or very expensive. Testing for all possible microorganisms is infeasible or very expensive. Possibility of water contamination is usually assessed by determining Possibility of water contamination is usually assessed by determining the number of coliform bacteria. the number of coliform bacteria. Escherachia coliEscherachia coli is exerted up to is exerted up to 4X104X101010 organisms per person per day. Presence of coliform is not a organisms per person per day. Presence of coliform is not a proof that water is contaminated; but absence indicates that the water proof that water is contaminated; but absence indicates that the water is free of pathogens. is free of pathogens.

Air Pollution Impacts on Water QualityAir Pollution Impacts on Water Quality

Major pollutants of air:Major pollutants of air: Dust particlesDust particles Industrial emissionIndustrial emission Vehicular exhaustVehicular exhaust CFCs (chlorofluorocarbons)CFCs (chlorofluorocarbons)

Air pollutants either settle down, or are washed down by rainfall, Air pollutants either settle down, or are washed down by rainfall, eventually affecting the water quality.eventually affecting the water quality.

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M. Shah Alam Khan Professor Institute of Water and Flood Management, Bangladesh University of...

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