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Philadelphia University Faculty of Engineering Department of Civil Engineering First Semester, 2013/2014. Environmental Engineering 343. Lecture 5: Water Quality. Water Quality Requirements.

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environmental engineering 343

Philadelphia University

Faculty of Engineering

Department of Civil Engineering

First Semester, 2013/2014

Environmental Engineering 343

Lecture 5:

Water Quality

water quality requirements
Water Quality Requirements
  • Water quality parameters - qualitatively reflect the effect of various impurities on the intended use of water
  • Standard Methods for the Examination of Water and Wastewater- Standard analytical test procedures which provide quantitative measurements of these parameters
water quality requirements1
Water Quality Requirements
  • Water quality parameters - qualitatively reflect the effect of various impurities on the intended use of water
  • Standard Methods for the Examination of Water and Wastewater- Standard analytical test procedures which provide quantitative measurements of these parameters
water quality requirements2
Water Quality Requirements

Water quality requirements vary according to proposed use of the water. Water unsuitable for one use may be satisfactory for another. These are set by the user. It represents a known or assume need and are based on prior experience of the user.

Water Quality Standards are set by a governmental agency and represent a statutory requirement

water quality requirements3
Water Quality Requirements
  • In-Stream standards – Streams have minimum quality standards based on its use. Wastewater discharged from human activities together with the geology and natural characteristics of the watershed.
  • Potable-water Standards – EPA ; WHO addresses turbidity, SS taste, odor, moderate dissolved inorganic; absence of organics, toxic substances and pathogens
  • Wastewater effluent standards- e.g. EPA standards for the discharge of wastewater. – require secondary treatment. Industrial wastewater must be pretreated to become compatible with receiving domestic WW.
  • Physical water-quality parameters
  • Chemical water-quality parameters
  • Biological water-quality parameters
  • Water quality requirements 
physical water quality p arameters
Physical Water-Quality Parameters


  • Suspended Solids
  • Turbidity
  • Colour
  • Taste
  • Odor
  • Temperature
solids impurities types of solids
Solids(impurities) types of Solids
  • Dissolved Solids (in Liquid) cannot be removed from liquid without accomplishing a phase change such as distillation, precipitation, adsorption, extraction or high pressure membrane
  • Suspended solids (filterable solids) those solids that can be filtered by a glass fiber filter disc can be removed from water by physical methods such as sedimentation, filtration and centrifugation.
  • Colloidal particles
    • Size in range between dissolved substances and suspended particles
    • Can be removed by high-force centrifugation or filtration – very small pore size
    • Measured by turbidity
1 0 suspended solids
1.0 Suspended Solids

Seldom found in groundwaters due to the natural filtering capacity of soils

Sources of Suspended Solids

Suspended Solids




Source – Surface Waters; Domestic WW; Industrial WW


-Plant Fiber

-Biological Solids (Agal Cells; Bacteria;)

Source – Surface Waters; Domestic WW; Industrial WW

Immiscible liquids



Source- Surface waters; Domestic WW and Industrial WW


Difference Between Dissolved, Suspensions and

Colloidal Solutions




Colloidal Solutions






Greater than 10

Between 10

and 10



Particle size

Less than 10





Invisible to naked eye not

Invisible to naked eye.

Visibility of

visible under powerful

Easily visible

Visible under powerful




Sedimentation of

Settle down due

Settle down under high

Do not settle down


to gravity


Filtration through

Residue is

No residue is formed

No residue is formed

filter power


Suspended- Larger than molecular size supported by buoyant and viscous forcesDissolved-molecules or ions held by molecular structure of waterColloids- Technically suspended but exhibits characteristics of dissolved

Water Pollution – The presence in water of impurities in such quantity and of such nature as to impair the use of the water for a stated purpose

  • Water quality is predicted on the intended use
  • Measured in mg/L
  • Sources (s):
    • Inorganic compounds such as clay, sand
    • Organic compounds such plant fibre, human wast
  • Effects (s):
    • Aesthetics
    • Adsorption point/centre for chemical and micro-organism
    • Health aspect
2 turbidity
2- Turbidity

Turbidity: The presence of suspended material such as clay, silt, finely divided organic mater, and other particulate material in water

The unit of measure is a Turbidity Unit (TU) or Nephlometric Turbidity Unit (NTU)

It’s a measure of the cloudiness

River values range from 2 to 200mg/L of SiO2

The EU drinking water upper limit is 10mg/L with a guideline value of 1mg/L

3 color
  • Color in water is caused by dissolved minerals, dyes or humic acids (decomposition of lignin) from plants.
    • Apparent Color: Color that is partly due to suspended solids (SS)
    • True Color (water treatment): Color that is contributed by dissolved solids (DS) after removal of SS
  • Color itself is not usually undesirable from the stand point of health- it indicates that water needs appropriate treatment
4 odor
4- Odor
  • Many organic and inorganic chemicals are odorous including algae and other organisms
  • H2S – hydrogen sulfide sometimes present in ground water and wastewater.
  • Threshold odor is determined by diluting a sample with odor –free water until the last perceptible odor is detectable (dilution factor)


  • Like odor, may be due to decaying micro-organisms or algae or due to high conc. of salts such as Ca & Mg
6 temperature
6- Temperature
  • One of the most important parameters in natural surface waters.
  • It influences the number and type of microorganism species present and their rate of activities;
    • affect most chemical reactions;
    • affect solubility of gases e.g oxygen decrease with increase temp. Conc of O2 around 8mg/L @ 25 degree Celsius
  • In WWTP, T above 36oC, the aerobic MO population tends to be less effective as WW purifiers
  • In rivers, as increased water temp reduces the amount of oxygen in water, thereby making river less desirable for fish, particularly salmonoids.
chemical water quality parameters
Chemical water Quality Parameters


  • TDS
  • Alkalinity
  • Hardness
  • Metals
  • Nutrients
  • pH
1 alkalinity
1- Alkalinity
  • Alkalinity measures the buffering capacity of the water against changes in pH; measuring the amount of acid needed to lower the pH in a water sample to a specific endpoint (4.5).
  • Water that has a high alkalinity can accept large doses of acids or bases without altering the pH significantly.
  • Waters with low alkalinity, such as rainwater or distilled water, can experience a drop in the pH with only a minor addition of an acid or base.
  • Alkalinity is expressed as mg (CaCO3)/L
  • In water the only significant contribution to alkalinity are carbonate species and free H+ and OH_
  • Acid base reaction

H2CO3 H+ +HCO3

HCO3- H+ + CO32-

2 hardness
2- Hardness
  • Measure of “multivalent” cations in water such as Ca2+,Mg2+, Fe2+, Mn3+
  • Ca2+and Mn2+are very important
    • Source (s):
      • natural mineral on earth
    • effect (s):
      • excessive soap usage (a waste !)
      • precipitate form on hardware
      • precipitate in pipe – temperature and pH increases

Total Hardness

  • The sum of the divalent metallic cations (Ca & Mg). These cations reacts with soap to form precipitate and with other ions present in water to form scale in boilers.
  • Measured as mg CaCO3/L
  • Two kinds of hardness:
    • carbonate hardness; temporary in characteristics, precipitated through boiling
    • non-carbonate hardness- chloride and sulfate; permanent in characteristic, eliminated through chemical softness / ion exchange
  • WT goal is to provide water with a hardness of less in the range of 75 to 120mg/L as CaCO3 by using softener
3 nutrients

Two nutrients are essential for the growth of organisms:

    • Nitrogen
    • Phosphorus
    • Both are indictors of water pollution

I-Nitrogen (N)

Source (s)

  • Elements for protein, chlorophyll and biological compounds
  • Decomposition of compounds
  • animals and human wastes, chemicals (fertilizers)

Effect (s)

    • NO3- poisoning to human specially babies below than 6month old and animals
    • NO3-> NO2-(in acidic condition) – will substitute O2 in blood vessel


Nitrogen; Exist in a form of “inorganic”, and “organic nitrogen

Measured by TKN “total Kjeldahl Nitrogen; is a measure of the total organic and ammonia nitrogen.


II-Phosphorus (P)

Exist in a form of “inorganic”, and “organic phosphate”.

Source (s):

  • readily present in soil
  • fertilizers
  • human wastes (“organic phosphate”
  • domestic wastes (element in detergent)

effects (s)

  • Cellular activity and aquatic plants
  • > 0.2 mg/L – disturb coagulation processes in water treatment plants
4 ions anions and cations
4-Ions – anions and cations
    • Major Ions (conc. In mg/L) such as Ca, Mg, Na, K, SO2, Cl, NO3, HCO3
    • Minor Ions: Conc in µg/L such as Al, Cu, Fe, Mn

Source (s):

    • Minerals readily available from nature
  • Effect (s):
    • Colour, odour, taste and turbidity
    • Deteriorate health (at high concentration)
4 ions anions and cations1
4-Ions – anions and cations

Metals – non toxic and toxic

Heavy metals: such as As, Ba, Cd, Cr, Pb, Hg, Se, Ag

Source (s)

  • human activities such as mining and industries

Effect (s):

  • dangerous disease such as cancer, abortion and deformation in newborn baby
5- pH
  • The negative log of the hydrogen ion concentration
  • pH of most mineral waters is 6 to 9
  • If pH is out side the range 6 – 9, it might kill off the active microbiological population including the aquatics organisms
  • pH is important in ensuring proper chemical treatment
electrical conductivity conductivity
electrical Conductivity/ conductivity
  • It is a measure of the ability of an aqueous solution to carry an electric current by the movement of ions.
  • The higher the numbers of ions, the higher magnitude of conductivity
  • Pure water has 0.05µS/cm (microsiemens/cm)
  • Sea water has about 40000 µS/cm
  • Groundwater 200-1500
6 dissolved oxygen

One of the most important measures of water quality is dissolved oxygen. Oxygen, although poorly soluble in water, is fundamental to aquatic life. Without free dissolved oxygen, streams and lakes become uninhabitable to aerobic organisms, including fish and most invertebrates.

It is found that the concentration of DISSOLVED OXYGEN in water is SMALL

Dissolved oxygen is inversely proportional to temperature, and

the maximum amount of oxygen that can be dissolved in water at 0°C is 14.6 mg/L to 7.6 at 30C.

dissolved oxygen
  • Dissolved oxygen in water is consumed by the oxidation of dissolved ammonia (NH3)and ammonium ion (NH4+)to form the nitrate ion (NO3⎯).

NH3(aq) + 2O2(aq) + OH NO3-(aq) + 2H2O(aq)

  • The most common substance oxidized by oxygen in water is ORGANIC MATTER OF BIOLOGICAL ORIGIN
  • Such organic matter (such as dead plant material like polymerized carbohydrate below), is oxidised by dissolved oxygen.
    • e.g. CH2O+O2(aq) CO2(g) + H2O(aq)
dissolved oxygen1
  • Under oxygen free (anaerobic) conditions dissolved organic matter will decompose if appropriate bacteria are present:
      • 2CH2O CH4+ CO2
  • Such anaerobic conditions are common in SWAMPS and at the bottom of deep lakes
  • The Methane (CH4) produced in this process bubbles up towards the surface of the swamps and is the reason that methane used to be known as ‘marsh 'or ‘swamp 'gas
organic substances
organic substances
  • The main element of organic compounds is Carbon.
  • Organic substances may be
    • Natural occurring organic substances includes protein, lipids, carbohydrates and plant pigments
    • Synthetic organic chemicals
      • Pesticides and agrochemicals
      • Surface active agent including emulsifier, wetting agent, foams, detergents
      • Halogenated hydrocarbons ( CHCl3, CHBr3, CHCl2Br, etc
  • Over 120 toxic organic compounds listed on the USEPA Priority Pollutant List including pesticides and solvents
analysis of organic substances
Analysis of Organic substances

Various parameters are used as a measure of the organic strength of wastewater:

  • BOD –Biochemical oxygen demand
  • COD –Chemical oxygen demand
  • TOC –Total organic carbon
  • VSS –Volatile suspended solid
biochemical oxygen demand bod
Biochemical Oxygen Demand (BOD)

The quantity of oxygen utilized by a mixed population of micro organisms to biologically degrade the organic matter in the wastewater under aerobic condition.

BOD is the most important parameter in water pollution control.

it is used a measure of organic pollution as a basis for estimating the oxygen

Needed for biological processes, as and indicator of process performance

Expressed in milligrams of oxygen required per liter of wastewater (mg/L).

biochemical oxygen demand
Biochemical Oxygen Demand

BOD : BOD5: is the amount of dissolved oxygen used up from the water by microorganisms as they break down organic material at 20C over a 5-day periods.

  • BOD5 for Rivers if > 5 mg/L, they considered polluted
  • BOD For MWW range 150-1000mg/L
chemical oxygen demand cod
chemical oxygen demand (COD)


  • Determine the amount of oxygen needed to oxidize the organics in a water or wastewater using a strong oxidizing chemical agent- Potassium dichromate rather than using micro-organisms as in BOD
  • It measures the total organic carbon with the exception of some aromatics such as benzene which are not oxidized in the reaction.
  • Indirectly measure amount of organic matter in the water sample
  • Faster determination of oxygen demand in a water sample, than BOD
  • It takes shorter time ( 2hrs) compared to 5 days for BOD5
  • The EU upper limit of 125mg/L for treated wastewaters prior to discharge to rivers
relation between cod and bod
Relation between COD and BOD
  • COD > BOD
  • COD ~ ultimate BOD
  • COD/BOD ~ 2, biodegradable organic
  • COD >> BOD, non-biodegradable organic
total organic carbon toc
total Organic Carbon- TOC
  • TOC- : measures all carbon as CO2 in mg/L
  • Inorganic carbon ( HCO3, CO2, CO3, etc) must be removed prior test by acidifying and aerating the sample.
  • Theoretically the COD is 2.66 times greater than TOC
biological water quality parameters
Biological water-quality parameters

the three most significant microbial groups are the bacteria, fungi, and protozoa. 

Bacteria have the primary role of decomposing wastewater compounds, forming settleable solids, and at times are the source of operational problems. 

Fungi are significant since many operational problems are caused by members of this group. 

Protozoa are microorganisms that play a key role as predators and help control the bacterial populations. 

composition of ww recall
99.9 % Water

0.1% Solids

Solids are divided into Organic and inorganic


Organic (70%)



Suspended Organics

(Colloidal –protein)

Dissolved Organics


Dissolved Inorganics

(metals, salts,P,N)

Composition of WW RECALL

Suspended Inorganics


Tertiary Treatment

Secondary Treatment

Dissolved Organics and Suspended Organics

Primary Treatment

60% SS; 30% BOD and Grit


Composition of WW


Biodegradable Organics

Suspended Solids

Soluble organics

Bacteria, virus etc.

Body waste, food waste rags, paper, biological cells

Protein (40-60%) – amino acids

Lipids (10%)- fats, oils and grease

Carbohydrates 25-50% - sugars starch, cellulose

Contain Carbon – exert an oxygen demand