Lecture Environmental Eng 2-2

8/17/2019 Lecture Environmental Eng 2-2

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Lecture 3: Wastewater

Characteristics

Wastewater Treatment

How human make use of nature


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Physical, chemical & biological

characteristics of wastewater

Physical properties

• Temperature

• Color

• Odor

• Turbidity

• Solids

Chemical constituents

• Organic – Proteins,carbohydrates, fats, oil& grease, pesticides,

phenols, surfactants,VOC, organic prioritypollutants.

• Inorganic – pH,chlorides, alkalinity,Chlorides, nitrogen,

phosphorus, heavymetals.

• Gases – N2, O2, CO2,H2S, NH3, CH4

Biological constituents

• Pathogenic organisms

• (1) Bacteria

• (2) Viruses

• (3) Protozoa

• (4) Helminths


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APHA 22 edition

Standard Methods for

the Examination ofWater and

Wastewater

Standard measurement for

• 2000 Physical & aggregate

properties

• 4000 Inorganic metallic

constituents

• 5000 Aggregate organic

constituents• 9000 Microbial

Examination

https://www.standardmethod

s.org/

https://www.standardmethods.org/https://www.standardmethods.org/https://www.standardmethods.org/https://www.standardmethods.org/https://www.standardmethods.org/


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Temperature

• Definition:

Indirect parameter to evaluate drinking water and wastewater, but very important fornatural surface water.

• Source:

(1) Ambient temperature.

(2) Disposal of hot industrial wastewater (i.e. POME disposal at 90C)

• Impact:(1) Affect aquatic life (i.e. warm water accelerate algae growth) and suitability for

beneficial uses.

(2) Affect settling characteristics of water processes (i.e. mixing, sedimentation).

(3) Temperature will affect water physical properties (i.e. viscocity, density, gas solubility)and reaction rates (i.e. biological, chemical).

(4) DO reduction as temperature increased (Whipple DO data).

• Measurement:

(1) In-situ temperature probe.

• Application:

40⁰C (Standard A and B of EQA 1974) for sewage, industrial and leachate discharge.

Physical

Properties


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In-situ temperature probe


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Color

• Definition: Pure water is colorless. Natural waters colored by impurities. Apparent color

caused by suspended solids (SS). True color caused by dissolved solids after SS removal.

• Source:

(1) Yellowish chocolate color of natural water – when natural waters mixed with tannins,

humic acid found in decaying leaves.

(2) Reddish color from underground – caused by the presence of iron oxide.(3) Wastewater changed color from gray to dark gray and ultimately black – due to the

formation of metallic sulfides, as the sulfides produced anaerobically reacted with metals

in wastewater.

(4) Some other colors (i.e. red blood) – might caused by the constituents in industrial

wastewater.

•

Impact:(1) Aesthetically, colored waters are unacceptable.

(2) May cause carcinogenic or mutanogenic (DNA altering) due to chlorinating the organic

compounds that caused the colorings.

• Measurement:

(1) Comparative method with standard color solution. Unit: TCU (True Color Unit), Hazen.

• Application: 100 ADMI (Standard A) and 200 ADMI (Standard B) for industrial and leachatedischarge. None in sewage discharge.

Physical

Properties


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Lovibond Color Comparator


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Odor

• Definition: Unpleasant smell.

• Source:

(1) Decomposition of organic matter (i.e. due to H2S produced by anaerobicmicroorganisms to reduce sulfate to sulfide).

(2) The existence of compounds that produce odor when react with anothercompound (i.e. additive impact when chlorines react with organic matter).

• Impact:(1) Dislike and unpleasantness for customers.

(2) Indicator for carcinogens.

• Measurement:

(1) Olfactometers – direct reading instruments.

(2) TON (Threshold Odor Number) test. TON corresponds to the greatest dilution of

the sample with odor free water at which an odor is just perceptible. TON = 3 isrecommended by Public Health Services, US.

(3) ED50 = Number of times an odorous air sample must be diluted before theaverage person can barely detect an odor in the diluted sample.

• Application:

TON = 3 is recommended by Public Health Services, US. Not regulated in EQA 1974.

Physical

Properties


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Odorous compounds associated with untreated

wastewater.

Odorous compound Odor, quality

Amines Fishy

Ammonia Ammoniacal

Diamines Decayed flesh

Hydrogen Sulfide Rotten eggs

Mercaptans (e.g. methyl and ethyl) Decayed cabbage

Mercaptans (e.g. T=butyl and crotyl) Skunk

Organic sulfides Rotten cabbage

Skatole Fecale matter


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Turbidity

• Definition: A measure of the light-transmitting of water.

• Source:

(1) Erosion of colloidal materials (i.e. clay, stone chirping).

(2) Colloids and flocs caused by soap and emulsifying agents.

• Impact:

(1) Give a picture of ‘milk’ (i.e. Tyndall effect).

(2) Cause taste and smell problems.

(3) Provide conducive environment for pathogenic microorganisms.

(4) Create problems to the other processes (i.e. disinfection of turbid water is verydifficult and costly).

• Measurement:

(1) Photometric method by measuring percent light from intensity absorbed ordispersed. Unit: JTU (Jackson Turbidity Unit), NTU (Nephelometry Turbidity Unit),FTU (Formazin Turbidity Unit).

• Application:

AWWA (American Water Works Association) limits of 0.1 FTU for drinking water. Notregulated under EQA 1974.

Physical

Properties


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What is Tyndall effect?

Tyndall effect can be observed whensunlight passes through the canopyof a dense forest. In the forest, mistcontains tiny droplets of water,which act as particles of colloiddispersed in air.


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Turbidity meter


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Coagulation & flocculation experiment using Jar test todetermine chemical coagulant dosage for minimum turbidity

(clear water).


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Solids

• Definition: All the matter in wastewater that remains as residue upon evaporation at103 to 105C.

• Source:

(1) Contain organic/inorganic particulates i.e. biological solids such as algal cell, bacteria.

• Impact:

(1) Undesirable due to its bitter taste.

(2) Will provide adsorption site for chemical/biological agents.(3) Some solids may be pathogenic organisms causing diseases.

• Measurement:

(1) Total solids burning them at 103 to 105C.

(2) Settleable solids settling them in Imhoff cone in a 60-minute period.

(3) Filterable solids filtering them through a glass-fiber filter (Whatman GF/C) with pore

size of 1.2 µm.(4) Volatile solids burning them in furnace at 550C.

• Application:

50 mg/L SS (Standard A, EQA 1974) and 100 mg/L (Standard B) for sewage, industrial andleachate discharge.

Physical

Properties


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Organic Matter

• Definition:

(1) Composed of a combination of carbon, hydrogen and oxygen. Nitrogen, sulfur, phosphorus and ironmay also be present.

(2) OM exists in a form of protein, carbohydrates, fats, oils & grease, surfactants, organic prioritypollutants, VOCs, pesticides, phenols.

(3) Two main components (a) easily degradable (b) not easily degradable (i.e. refractory, recalcitrant)

(4) Easily degradable organics through (a) utilization as food by microorganisms (b) oxidation (c)reduction (d) aerobic processes (e) anaerobic processes

• Source:

(1) Originated from plants and animal.

(2) Synthesis of organic compounds.

• Impact:

(1) Contaminate the receiving waters.

• Measurement:(1) BOD Test (2) COD Test (3) TOC (Total Organic Carbon) Test (4) SOUR Test

• Application:

(1) 20 mg/L BOD and 120 mg/L of COD (Standard A, EQA 1974) and 50 mg/L BOD and 200 mg/L COD(Standard B) for sewage discharge.

(2) 20 mg/L BOD (Standard A, EQA 1974) and 50 mg/L BOD (Standard B) for industrial discharge.

(3) 20 mg/L BOD and 400 mg/L COD (Standard B) for leachate discharge.

Chemical

Constituents


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What are organic matters?

Proteins (40-60%)The combination of a large number of amino acids.

Contains C, H, O and N. Thus, major source of nitrogen in wastewater.

If present abundantly, produce extremely foul order during decomposition.

Carbohydrates (25-50%)

Include sugars, starches, cellulose and wood fibers.

Contains C, H and O.

Surfactants

Mainly fromsynthetic

detergent.

VOCsOrganic compoundsthat have a boilingpoint < 100C or avapor pressure

>1mm Hg (i.g. vinyl

chloride).

Phenols

Mainlyfrom

petroleumproducts.

Fats,oils & grease (10%)

Fats & oils are from the foodstuffs.

Grease are from shops, garages andstreets.

Pesticides

Fromagriculturaland parks

surface runoff.

Org. PriorityPollutants

Either

carcinogenic,

mutagenic,

teratogenic or

acute toxic.


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BOD

test

COD

test

TOC

test

SOUR

test


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Biochemical Oxygen Demand (BOD)

BOD test

• Measure O2 utilized from sample placed in air tight containers and kept inincubator for specified number of days.

• BOD bottles with size 300 mL are used, incubated at 20⁰C for 5 days.

• BOD520 – BOD at temperature 20⁰C for 5 days.

•Require (i) oxygen-saturated water during aeration (ii) require seeding ofmicroorganism in wastewater samples

• Presence of toxic matters may inhibit microorganism activity. Therefore,BOD results may be inaccurate.

BOD calculation

= ( ) = initial DO= final DO = Decimal fraction of sample in 300 mL bottle


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• The measurement of the dissolved oxygen used by microorganismsin the biochemical oxidation of organic matter.

• 5-day BOD – biodegradation is only 60-70% complete.

• 20-day BOD – about 95-99% complete.

• Assumption: BOD degradation according to first order.


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=

=

=

=

= −

= remaining BOD at t=0 @ultimate BOD

= remaining BOD at time t

= Thus, 5-day BOD means 5 = = ( −) =of wastewaterK value dependent of temperature

= (−) = reaction rate constant attemperature T

= 1.056


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• Analysis Of BOD data is used toevaluate and ultimate BODvalues for design purposes.

• Using least square method orExcel

Observe these two functions.

1 − at which

= 1 6−3

After expansion and simplification

= 1 6−3

Or, in linear form

3 = 236/3 t

−/3

Y axis =

X axis =

Slope =

/ Y interception = −/3


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Chemical Oxygen Demand (COD)

COD test

• Used to measure the organic matter in industrial and municipalwastewater that contain compounds that are toxic to biological life.

• The oxygen equivalent of organic matter that can be oxidized ismeasured by using a strong chemical oxidizing agent (potassium

dichromate) in an acidic medium.• The test must be performed at an elevated temperature.

• A catalyst (silver sulfate) is required to aid the oxidation of certainclasses of organic compounds.

• COD>BOD because more compounds can be chemically oxidized

than can be biologically oxidized.• BOD/COD varies from 0.4 to 0.8

272− + → +3 2 2


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Total Organic Carbon (TOC)

TOC test

• Is performed by injecting a known quantity of sampleinto a high-temperature furnace or chemically oxidizingenvironment.

• The organic carbon is then oxidized to CO2 (measuredby infrared analyzer) in the presence of catalyst.

• BOD/TOC varies from 1.0 to 1.6.

• Not easily degraded organics = Lo – (COD or TOC)

•Examples of not easily degraded organics: tannin acid,lignin, cellulose, part of wooded plant that is heatresistance,phenol, benzene, alkyl benzene sulphonate(ABS), insecticides, herbicides.


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Specific Oxygen Uptake Rate (SOUR)

SOUR test

• An accepted method for indicating the biological activity of an activated sewage sludge mixed

liquor or aerobically digesting sludge.

• Standard Method 2710B.

• Measure O2 consumption rate of involved microbes.

•

Measurement Apparatus: Manometric or respirometric device.• Procedures: Measure initial DO and record DO level at every 1 minute or less, for 15 minutes

or until DO < 1 mg/L.

• Limitation: Sludge has to be less or equal to 2% Total Solids (TS).

• Data presentation: Plot DO (mg/L) vs time (min).

SOUR calculation

= ( 2.) () 60(ℎ )

= specific oxygen uptake rate ( .) = Total Solids concentration ()

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Lecture Environmental Eng 2-2

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