Wastewater CharacteristicsWastewater Characteristics

CE - 370CE - 370

Importance of CharacteristicsImportance of Characteristics

The degree of treatment depends on:The degree of treatment depends on:Influent characteristicsInfluent characteristicsEffluent characteristicsEffluent characteristics

Impurities come from:Impurities come from:Domestic activitiesDomestic activitiesIndustrial activitiesIndustrial activitiesCommercial activitiesCommercial activities

Typical characteristics are shown in the Typical characteristics are shown in the following Tablefollowing Table

ConstituentsConcentration

StrongMediumWeak

Total Solids1250800450

TDS890560350

Fixed TDS295295185

Volatile TDS595265165

TSS360240100

Fixed SS1457525

Volatile SS21516575

Settleable Solids (ml/l)753

BOD5400200100

TOC29014575

COD910455230

Total Nitrogen754016

Organic Nitrogen40208

Free Ammonia35208

Nitrite000

Nitrate000

Total Phosphorous1584

Organic Phosphorous 531

Inorganic Phosphorous1053

Chlorides834221

Alkalinity (CaCO3)20010050

Grease40205

CharacteristicsCharacteristics

PhysicalPhysical ChemicalChemical BiologicalBiological

Physical CharacteristicsPhysical Characteristics

TurbidityTurbidity Caused by the presence of organic suspended solidsCaused by the presence of organic suspended solids

Color Color Is light tan if fresh (2 to 6 hours old)Is light tan if fresh (2 to 6 hours old) Is grey if older than 6 hours due to biochemical oxidation Is grey if older than 6 hours due to biochemical oxidation

in collection systemin collection system Is dark grey or black if undergone extreme biochemical Is dark grey or black if undergone extreme biochemical

oxidation under anaerobic conditions (production of oxidation under anaerobic conditions (production of sulfides, particularly ferrous sulfide)sulfides, particularly ferrous sulfide)

Hydrogen sulfide is produced under anaerobic condition, Hydrogen sulfide is produced under anaerobic condition, which reacts with ferrous ions and produce ferrous sulfidewhich reacts with ferrous ions and produce ferrous sulfide

Physical CharacteristicsPhysical Characteristics

OdorOdorSoapy or oily odor if fresh (not offensive)Soapy or oily odor if fresh (not offensive)Stale, very offensive, if undergone extreme Stale, very offensive, if undergone extreme

anaerobic biochemical oxidation, due to anaerobic biochemical oxidation, due to production of compounds such as hydrogen sulfide production of compounds such as hydrogen sulfide

Total solidsTotal solidsSuspendedSuspendeddissolveddissolvedVolatile (evaporate at 550Volatile (evaporate at 550 C) C)Fixed (remain after ignition)Fixed (remain after ignition)settleablesettleable

Physical CharacteristicsPhysical Characteristics

Temperature is higher than that of water Temperature is higher than that of water supplysupplyImportant parameter, particularly for biological Important parameter, particularly for biological

processesprocesses

Physical characteristics of industrial Physical characteristics of industrial wastewater vary depending on the source of wastewater vary depending on the source of the wastewaterthe wastewater

Chemical CharacteristicsChemical Characteristics

Chemical Oxygen Demand (COD)Chemical Oxygen Demand (COD)Is a measure of organic materials (is based on Is a measure of organic materials (is based on

measurement of the amount of oxidizing agent measurement of the amount of oxidizing agent required to oxidize the organic materials)required to oxidize the organic materials)

Total Organic Carbon (TOC)Total Organic Carbon (TOC)Is a measure of organic materials (based on Is a measure of organic materials (based on

measurement of carbon in the organic materials by measurement of carbon in the organic materials by combustion and measurement of COcombustion and measurement of CO22 evolves) evolves)

Chemical CharacteristicsChemical Characteristics Organic Nitrogen (amount of nitrogen in organic Organic Nitrogen (amount of nitrogen in organic

compounds such as protein and urea)compounds such as protein and urea) Ammonia nitrogen (NHAmmonia nitrogen (NH33)) Nitrite nitrogen (NONitrite nitrogen (NO22

--)) Nitrate nitrogen (NONitrate nitrogen (NO33

--)) Organic Phosphorous (in protein)Organic Phosphorous (in protein) Inorganic phosphorous (phosphates, POInorganic phosphorous (phosphates, PO44

--)) Chlorides (ClChlorides (Cl--)) Sulfates (SOSulfates (SO44

-2-2)) pHpH AlkalinityAlkalinity

Chemical CharacteristicsChemical Characteristics Grease (interferes with oxygen transfer in activated Grease (interferes with oxygen transfer in activated

sludge processes)sludge processes) Heavy metals such asHeavy metals such as

Mercury (Hg)Mercury (Hg) Arsenic (As)Arsenic (As) Lead (Pb)Lead (Pb) Zinc (Zn)Zinc (Zn) Cadmium (Cd)Cadmium (Cd) Copper (Cu)Copper (Cu) Nickel (Ni)Nickel (Ni) Chromium (Cr)Chromium (Cr) Silver (Ag)Silver (Ag)

Chemical CharacteristicsChemical Characteristics

Priority Pollutants (organic and inorganic) are:Priority Pollutants (organic and inorganic) are:CarcinogenicCarcinogenicMutagenicMutagenicTeratogenicTeratogenicHigh acute toxicHigh acute toxic

Biological CharacteristicsBiological Characteristics

Biochemical Oxygen Demand (BODBiochemical Oxygen Demand (BOD55))The amount of oxygen needed to stabilize organic The amount of oxygen needed to stabilize organic

matter by micro-organismsmatter by micro-organisms Time (5 days)Time (5 days) Temperature (20Temperature (20 C) C)

Nitrogenous Oxygen DemandNitrogenous Oxygen DemandThe amount of oxygen needed to convert organic The amount of oxygen needed to convert organic

and ammonia nitrogen to nitrates by nitrifying and ammonia nitrogen to nitrates by nitrifying bacteriabacteria

Wastewater Microbial LifeWastewater Microbial Life

Wastewater containsWastewater contains BacteriaBacteria ProtozoaProtozoa FungiFungi VirusesViruses AlgaeAlgae RotifersRotifers nematodesnematodes

Sources Sources Soil (through infiltration)Soil (through infiltration) Human intestines (Human intestines (Escherichia coliEscherichia coli and and Aerobacter aerogenesAerobacter aerogenes))

Biochemical Oxygen DemandBiochemical Oxygen Demand

OrganismsOrganisms use organic matter, in wastewater, as a substrateuse organic matter, in wastewater, as a substrate Need oxygen for respirationNeed oxygen for respiration Produce end-products such as COProduce end-products such as CO22 and H and H22OO

BOD is conducted under aerobic conditionsBOD is conducted under aerobic conditions Up to 10 to 12 days, OUp to 10 to 12 days, O22 demand will be for oxidation demand will be for oxidation

of carbonaceous materialsof carbonaceous materials

cellsnewNHOHCOOOrganics microbesAerobic

3222

Biochemical Oxygen DemandBiochemical Oxygen Demand

After 10 to 12 days, the NHAfter 10 to 12 days, the NH33 will be oxidized to nitrite will be oxidized to nitrite

and then nitrateand then nitrate

The next two Figures show:The next two Figures show: the BOD curve for both stagesthe BOD curve for both stages Carbonaceous stageCarbonaceous stage

productsendenergycellsnewHNOHONO

productsendenergycellsnewOHHNOONH

rNitrobactebacteriaNitrate

asNitrosomonbacteriaNitrite

2222

2232

3)(

22

22)(

23

Carbonaceous StageCarbonaceous Stage

Removal of organic matter is a pseudo-first-order Removal of organic matter is a pseudo-first-order reactionreaction

dC/dt = rate of removal of organic matterdC/dt = rate of removal of organic matter k = rate constant to the base ek = rate constant to the base e C = concentration of organic matter remaining at time (t)C = concentration of organic matter remaining at time (t)

kCdt

dC

Carbonaceous StageCarbonaceous Stage

Rearrange and integrate the equationRearrange and integrate the equation

CC00 = concentration of organic matter initially = concentration of organic matter initially

C = oxidizable organic matter remaining at time (t)C = oxidizable organic matter remaining at time (t) t = test durationt = test duration

kt

CC

C

C

t

eC

C

ktC

dtkC

dC

0

0

0

0

]ln

Carbonaceous StageCarbonaceous Stage

Since the amount of organic matter oxidized is Since the amount of organic matter oxidized is proportional to the amount of oxygen required, then:proportional to the amount of oxygen required, then:

C C L (where L is the BOD remaining at time t) L (where L is the BOD remaining at time t)

SimilarlySimilarly CC00 L L00

Then,Then,

L = BOD remaining at time tL = BOD remaining at time t LL00 = ultimate first-stage or carbonaceous BOD = ultimate first-stage or carbonaceous BOD kk11 = rate constant to the base e = rate constant to the base e t = test durationt = test duration KK11 = rate constant to the base 10 = rate constant to the base 10

tKtkeL

L11 10

0

Carbonaceous StageCarbonaceous Stage

Thus:Thus:

So, BOD exerted (y) up to time (t) is:So, BOD exerted (y) up to time (t) is:

tK

tk

LL

and

eLL

1

1

100

0

)101(10

)1(

11

11

000

000

tKtK

tktk

LLLy

or

eLeLLy

ExampleExample

ExampleExampleA wastewater has a BODA wastewater has a BOD55 of 200 mg/l, and the k of 200 mg/l, and the k11 value is value is

0.34 day0.34 day-1-1. Determine the ultimate first-state BOD, L. Determine the ultimate first-state BOD, L00..

SolutionSolution

y = Ly = L0 0 (1 - e(1 - e-k1t-k1t))

200 = L200 = L0 0 [1 - e[1 - e-(0.34)(5)-(0.34)(5)]]

Thus, LThus, L00 = 245 mg/l = 245 mg/l