wastewater characteristics1

8/7/2019 Wastewater Characteristics1

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Wastewater Characteristics

Part-1


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WastewaterWastewater liquid waste (wastewater) can be classified as (based on source)

Domestic

Industrial

Storm


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Domestic : water used for normal activity in homes,businesses and institutions. Domestic wastewater isreadily treatable.

Industrial:

The character of industrical wastewater dependson the type of industry.

Some industrial wastewaters can be treated thesame as domestic wastes without difficulty.

Others may contain toxic substances or high

percentages of organic materials or solids whichmake treatment difficult.

In such cases, the industrial plant may have topretreatits wastewater to remove these pollutants orreduce them to treatable levels before they are

accepted into a general treatment facility.


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Storm:

usually low in pollutants.

Great amounts of storm water can interferewith treatment efficiency in two ways:

Storm water may cause too much dilution ofthe wastewater.

At the same time, it may cause hydraulicoverloading of the plant.


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Wastewater characteristicsWastewater characteristics General classes of wastewater constituentsGeneral classes of wastewater constituents

such assuch as physicalphysical,, chemicalchemical,, biological.biological.

An understanding of the nature of wastewater isAn understanding of the nature of wastewater isessential inessential in

the design and operation of collection,the design and operation of collection,

treatment, and reuse facilities,treatment, and reuse facilities,

and in the engineering management ofand in the engineering management ofenvironmental quality.environmental quality.


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ChemicalChemical pHpH

BODBOD

CODCOD

(N)(N)

(P)(P)

(SS)(SS)

(DO)(DO)

Pollution indicators

Physical

(Turbidity)(Color)

(Odor)

Biological

(Coliform)

(Pathogen)

Proper sampling and analytical techniques are offundamental importance in the characterization ofwastewater


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Wastewater characteristics

1. ORGANIC MATTER Carbohydrates/ Sugars, proteins, lipids; Toilet wastes, cleaning, food wastes,

COD Chemical Oxygen Demand (mg O2/l) A measure of the oxygen-consuming capacity of organic matter

present in wastewater. COD is expressed as the amount of oxygen consumed from a

chemical oxidant (KK22CrCr

22OO77 ) in mg/Lduring a specific test.

BOD Biochemical Oxygen Demand (mg O2/l)

The quantity of oxygen (O2) that microorganism use per litrewater, during a continuous period of 5 days, at20C. The rate atwhich organisms use the oxygen in wastewater while stabilizingdecomposable organic matter under aerobic conditions.


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BOD5/COD > 0.6 (biodegradable)

BOD5/COD < 0.2 (non-biodegradable,

recalcitrant)

Domestic wastewater: BOD/COD = 0.4;

Dairy wastewater: BOD/COD = 0.6 0.7


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Biological oxygen demandBiological oxygen demand

(BOD) is a measure of the oxygen required to(BOD) is a measure of the oxygen required tostabilize or decompose the organic matter in astabilize or decompose the organic matter in awater body, over a fivewater body, over a five--day period at20day period at20C.C.

The soThe so--called 5called 5--day BOD measures the amount ofday BOD measures the amount ofoxygen consumed by biochemical oxidation ofoxygen consumed by biochemical oxidation ofwaste contaminants in a 5waste contaminants in a 5--day period.day period.

The total amount of oxygen consumed when theThe total amount of oxygen consumed when thebiochemical reaction is allowed to proceed tobiochemical reaction is allowed to proceed tocompletion is called the Ultimate BOD.completion is called the Ultimate BOD.


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CODCOD

The chemical oxygen demand is the totalThe chemical oxygen demand is the totaloxygen consumed by the chemicaloxygen consumed by the chemical

oxidation of that portion of organicoxidation of that portion of organicmaterials in water which can be oxidizedmaterials in water which can be oxidizedby a strong chemical oxidant.by a strong chemical oxidant.

The oxidant used is a mixture ofThe oxidant used is a mixture ofpotassium dichromate andpotassium dichromate and sulfuricsulfuric acid.acid.


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There is no generalized correlation between the 5There is no generalized correlation between the 5--daydayBOD and the ultimate BOD.BOD and the ultimate BOD.

Similarly there is no generalized correlation betweenSimilarly there is no generalized correlation betweenBOD and COD.BOD and COD.

It is possible to develop such correlations for specificIt is possible to develop such correlations for specificwaste contaminants in a specific waste water stream .waste contaminants in a specific waste water stream .

This is because the composition of any waste waterThis is because the composition of any waste waterstream is different.stream is different.


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Typical BOD valuesTypical BOD values

Most of rivers have a 5Most of rivers have a 5--day carbonaceous BOD below 1day carbonaceous BOD below 1 mg/L.mg/L.

Moderately polluted rivers may have a BOD value in the rangeModerately polluted rivers may have a BOD value in the range

of2 to 8of2 to 8 mg/L.mg/L.

Municipal sewage that is efficiently treated by a threeMunicipal sewage that is efficiently treated by a three--stagestageprocess would have a value of about20process would have a value of about20 mg/L or less.mg/L or less.

Untreated sewage varies, but averages around 600

Untreated sewage varies, but averages around 600

mg/L inmg/L inEurope and as low as 200Europe and as low as 200 mg/L in the U.S.mg/L in the U.S.


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2. NITROGEN (N)

Organic nitrogen: proteins, amino acids, urea,;

Ammonia nitrogen (NH3, NH4+);

Nitrate- (NO

3

-

), nitrite nitrogen (NO2

-

); Nitrogen gas (N2).

TotalKjeldahlnitrogen (TKN)

Nitrogen in the form oforganic proteins or theirdecomposition productammonia, as measured by thekjeldahl Method.

all organic and inorganic nitrogen forms are convertedto nitrate with a sulfuric digestion. The nitrates arephotometrically quantified to yield Total Nitrogen


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3 PHOSPHORUS (P)

Organic phosphorus: foodstuff, toilet wastes,animal wastes;

Orthophosphate (HPO4-): fertilizer; Polyphosphate: detergents.

Eutrophication

Natural process in which surface waters receiveinputs of nitrates and phosphates resulting inovernourishment of aquatic ecosystems.

-> Algae bloom, anaerobic surface water


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4. Solids

Wastewater contains a variety of solids varying from ragWastewater contains a variety of solids varying from ragto colloidal materialto colloidal material

Content of solids in wastewater is often used to assessContent of solids in wastewater is often used to assessthe reuse potential of a wastewater and to determine thethe reuse potential of a wastewater and to determine the

most suitable type of operations and processes for itsmost suitable type of operations and processes for itstreatmenttreatment

ImhoffImhoff conecone test fortest for settleablesettleable solidssolids

60% of suspended solids in60% of suspended solids inmunicipal wastewater aremunicipal wastewater are settleablesettleable..



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0.45~2m


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However,However, TSSTSS andand BODBOD are the twoare the twouniversally used effluent standards touniversally used effluent standards to

evaluate the performance of treatmentevaluate the performance of treatmentplants for regulatory control purposes.plants for regulatory control purposes.


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5..Priority pollutants5..Priority pollutants

The priority pollutants are a subset of "toxicThe priority pollutants are a subset of "toxicpollutants" as defined in the Clean Water Actpollutants" as defined in the Clean Water Act(USA) .(USA) .

It refers to a list of 129 specific pollutants thatIt refers to a list of 129 specific pollutants thatincludesincludes heavy metalsheavy metals andand specific organicspecific organicchemicalschemicals..

These 1

26 pollutants were assigned a high

These 1

26 pollutants were assigned a highpriority for development of water qualitypriority for development of water quality

criteria and effluent limitation guidelinescriteria and effluent limitation guidelinesbecause they are frequently found in wastewater.because they are frequently found in wastewater.


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Priority pollutantsPriority pollutants

Heavy MetalsHeavy Metals (Total and Dissolved):(Total and Dissolved): occur only atoccur only at

trace levels in water, but are very toxic and tend totrace levels in water, but are very toxic and tend to

accumulate; As, Cd, Cr, Pb, Hg, Znaccumulate; As, Cd, Cr, Pb, Hg, Zn

PesticidesPesticides: DDT, Aldrin, Chlordane, Endosulfan, Endrin,: DDT, Aldrin, Chlordane, Endosulfan, Endrin,Heptachlor, and DiazinonHeptachlor, and Diazinon

Polycyclic Aromatic Hydrocarbons (PAHs)Polycyclic Aromatic Hydrocarbons (PAHs):: a familya family

of semiof semi--volatile organic pollutants; two main sources :volatile organic pollutants; two main sources :

spilled or released petroleum products and combustionspilled or released petroleum products and combustion

products that are found in urban runoff.products that are found in urban runoff.

Polychlorinated biphenyls (PCBs)Polychlorinated biphenyls (PCBs):: widespread use inwidespread use in

electrical transformers and hydraulic equipmentelectrical transformers and hydraulic equipment


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wastewater characteristics1

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