SECONDARY TREATMENTSECONDARY TREATMENT

• Main aim is to remove BOD (organic matter) to avoid Main aim is to remove BOD (organic matter) to avoid oxygen depletion in the recipientoxygen depletion in the recipient

• Microbial actionMicrobial action• Aerobic/anaerobic microorganisms that decompose Aerobic/anaerobic microorganisms that decompose

organic materialorganic material• Aerobic degradation is much faster and easier to Aerobic degradation is much faster and easier to

controlcontrol• Activated sludgeActivated sludge treatment – bacteria suspended in the treatment – bacteria suspended in the

wastewaterwastewater (most common (most common typetype of biological WWT) of biological WWT)• SludgeSludge contains bacteria contains bacteria• ActivatedActivated because they are hungry (spend some time because they are hungry (spend some time

without food (easily biodegradable organics) in the without food (easily biodegradable organics) in the settling tank)settling tank)

ACTIVATED SLUDGEACTIVATED SLUDGE TREATMENT TREATMENT

Organic material + OOrganic material + O22 + nutrients + microorganisms + nutrients + microorganisms new cells + COnew cells + CO22 + H + H22OO

• Same process occurs in natureSame process occurs in nature• Protection of water qualityProtection of water quality• Controlled processControlled process• Intensified processIntensified process• Bacteria are reused – recycling from secondary Bacteria are reused – recycling from secondary

clarifier (clarifier (recycling sludge or returned activated sludgerecycling sludge or returned activated sludge)) • Microbial growth (continuous food supply) – bacteria Microbial growth (continuous food supply) – bacteria

have to be removed have to be removed waste activated sludge waste activated sludge (excess (excess sludge)sludge)

AERATION TANKAERATION TANK

• Oxygen has to be provided – aeration tank (reactor)Oxygen has to be provided – aeration tank (reactor)• Wastewater = liquid containing food (organic Wastewater = liquid containing food (organic

pollution)pollution)• Biomass (bacteria – concentrated by recycling)Biomass (bacteria – concentrated by recycling)• Combination of the liquid and microorganisms Combination of the liquid and microorganisms

undergooing aeration = mixed liquorundergooing aeration = mixed liquor• The suspended solid = mixed liquor suspended solid The suspended solid = mixed liquor suspended solid

(MLSS)(MLSS)• Biomass is mostly organic material – it can be Biomass is mostly organic material – it can be

measured as VSS (volatile suspended solid) - MLVSSmeasured as VSS (volatile suspended solid) - MLVSS

ACTIVATED SLUDGE PLANTACTIVATED SLUDGE PLANT

recycling sludge recycling sludge

QQ33, , SS33, X, X33QQ11, S, S11, , XX11

VV22,, XX22, S, S22

QQ44, S, S44, X, X44

OO22

QQ55, S, S55, X, X55

excess sludge excess sludge

inletinlet effluenteffluent

aeration tankaeration tank sedimentation basinsedimentation basin

Q: wastewater volume (mQ: wastewater volume (m33/d)/d)

S: BODS: BOD55 concentration = soluble substrate (mg/L concentration = soluble substrate (mg/L S S11=120-400 mg/L)=120-400 mg/L)

X: concentration of biomass (sludge) (mg/L, g/L X: concentration of biomass (sludge) (mg/L, g/L X X22=3-6 g/L)=3-6 g/L)

V: volume (mV: volume (m33))

Mass balance: Inflow rate = outflow rateMass balance: Inflow rate = outflow rate

QQ11 = = QQ = Q = Q33+Q+Q5 5 Q Q33 = Q = Q11-Q-Q55 (Q(Q33 = Q-Q = Q-Qww))

In the aeration tank and in outflow streams the same dissolved organic In the aeration tank and in outflow streams the same dissolved organic matter (substrate) concentrationmatter (substrate) concentration

SS22 = S = S33 = S = S44 = S= S55 = = SS (there is a profile in AS tank) (there is a profile in AS tank)

In waste streams the same biomass concentrationIn waste streams the same biomass concentration

XX44 = X = X55 = = XXRR

QQ33, S, S33, , XX33QQ11, S, S11, , XX11

VV22,, XX22, S, S22

QQ44, , SS44, X, X44QQ55, S, S55, X, X55

((QQ-Q-Qww), S, ), S, XXeeQQ, S, S00, , XX00

VV,, XX, S, S

QQrr, , SS, X, XRRQQww, S, X, S, XRR

V: reactor (aeration tank) volume, mV: reactor (aeration tank) volume, m33

Q: influent flow rate (mQ: influent flow rate (m33/d)/d)

XX00: concentration of biomass in the effluent (g VSS/m: concentration of biomass in the effluent (g VSS/m33))

QQww: waste sludge flow rate(m: waste sludge flow rate(m33/d)/d)

XXee: concentration of biomass in effluent (g VSS/m: concentration of biomass in effluent (g VSS/m33))

XXRR: concentration of biomass in return line from clarifier (g VSS/m: concentration of biomass in return line from clarifier (g VSS/m33))

Treatment efficiencyTreatment efficiency (in terms of soluble BOD) (in terms of soluble BOD)::

E = (SE = (S00-S)/S-S)/S00

Recycle rateRecycle rate::

ratio of return sludge volume to raw wastewater volumeratio of return sludge volume to raw wastewater volume

R = QR = Qrr/Q/Q

((QQ-Q-Qww), S, ), S, XXeeQQ, S, S00, , XX00

VV,, XX, S, S

QQrr, , SS, X, XRRQQww, S, X, S, XRR

Volumetric organic loading rate (volumetric load):Volumetric organic loading rate (volumetric load):

Organic matter BOD (or COD) applied to the aeration tank Organic matter BOD (or COD) applied to the aeration tank volume per dayvolume per day

BBVV= Q= Q××SS00/V/V = 0.3-3 kg BOD = 0.3-3 kg BOD55/m/m33dd

((QQ-Q-Qww), S, ), S, XXeeQQ, S, S00, , XX00

VV,, XX, S, S

QQrr, , SS, X, XRRQQww, S, X, S, XRR

Sludge loadSludge load = F/M (food to microorganisms) ratio = F/M (food to microorganisms) ratio: :

Organic matter load applied to unit mass of sludge (biomass)Organic matter load applied to unit mass of sludge (biomass)

BBX X = Q= Q ×× SS00 / (V/ (V ×× X) kg BOD X) kg BOD55/kg /kg VVSS/dSS/d

0.8-1.5 kg BOD0.8-1.5 kg BOD55/kg /kg VVSS/d SS/d high load high load

0.3-0.8 kg BOD0.3-0.8 kg BOD55/kg /kg VVSS/d SS/d normal load normal load

0.05-0.3 kg BOD0.05-0.3 kg BOD55/kg /kg VVSS/d SS/d low load low load

((QQ-Q-Qww), S, ), S, XXeeQQ, S, S00, , XX00

VV,, XX, S, S

QQrr, , SS, X, XRRQQww, S, X, S, XRR

Sludge productionSludge production (we grow bacteria: product-inflow) (we grow bacteria: product-inflow)::

FFSPSP = X = Xee××(Q-Q(Q-Qww)+ X)+ XRR××QQWW – (X– (X00××QQ00))

can be expressed by yield (= g biomass produced/g substrate can be expressed by yield (= g biomass produced/g substrate utilized)utilized)

Excess sludge productionExcess sludge production::

QQWW××XXRR

00

((QQ-Q-Qww), S, ), S, XXeeQQ, S, S00, , XX00

VV,, XX, S, S

QQrr, , SS, X, XRRQQww, S, X, S, XRR

Sludge age (solid retention time): Sludge age (solid retention time):

average time during which the sludge has remained in the systemaverage time during which the sludge has remained in the system

SRT = SRT = X X = = (V(V ×× X) X)/ / (X(Xee××(Q-Q(Q-Qww) + X) + XRR××QQWW)) [[dd]]

kg sludge present in the akg sludge present in the aereration tankation tank

sludge leaving the system kg/dsludge leaving the system kg/d

SRT < 2 days SRT < 2 days high load high load

SRT = 2-6 days SRT = 2-6 days normal load normal load

SRT > 6 days SRT > 6 days low load low load

((QQ-Q-Qww), S, ), S, XXeeQQ, S, S00, , XX00

VV,, XX, S, S

QQrr, , SS, X, XRRQQww, S, X, S, XRR

SLUDGE VOLUME INDEXSLUDGE VOLUME INDEX

SVI = (settled volume of sludge, mL/L)(1000 mg/g)/(suspended solids, mg/L) = mL/g

SLUDGE VOLUME INDEXSLUDGE VOLUME INDEX

SLUDGE VOLUME INDEXSLUDGE VOLUME INDEX

• Mixed liquors with a 3000 mg/L TSS Mixed liquors with a 3000 mg/L TSS concentration that settles to a volume of concentration that settles to a volume of 300 mL in 30 minutes in a 1-L cylinder 300 mL in 30 minutes in a 1-L cylinder would have an SVI of 100 mg/L – good would have an SVI of 100 mg/L – good settling characteristicssettling characteristics

• SVI>150 filamentous growthSVI>150 filamentous growth

TERTIARY TREATMENT TERTIARY TREATMENT (PHYSICO-CHEMICAL TREATMENT)(PHYSICO-CHEMICAL TREATMENT)

• pH controlpH control

• Nitrogen removal (ammonia stripping)Nitrogen removal (ammonia stripping)

• Stripping (volatile organic compounds)Stripping (volatile organic compounds)

• FiltrationFiltration

• AdsorptionAdsorption

• Chemical phosphorus removalChemical phosphorus removal

pH CONTROLpH CONTROL

• Treatment processes (biological, chemical) have Treatment processes (biological, chemical) have optimal pH rangeoptimal pH range

• Communal wastewaters: pH between 6.5-8.5Communal wastewaters: pH between 6.5-8.5• If not If not pH adjustments (biological treatment) pH adjustments (biological treatment)• + Assuring the stability of pH (buffering capacity) – + Assuring the stability of pH (buffering capacity) –

NaHCONaHCO33

pH CONTROLpH CONTROL• CaO, Ca(OH)CaO, Ca(OH)22 = lime= lime

– Cheap, but with COCheap, but with CO22 CaCOCaCO33 (not suitable for pH control) (not suitable for pH control)

– Only rough controlOnly rough control

• NaOHNaOH– ExpensiveExpensive

– No effect of CONo effect of CO22

– Fine controlFine control

• HH22SOSO44

– Easy to calculate and apply accuratelyEasy to calculate and apply accurately

– Concentrated sulphuric acid is dangerousConcentrated sulphuric acid is dangerous

• HClHCl– Good controlGood control

– Volatile – corrosionVolatile – corrosion

• COCO22

– Very rough control (weak acid)Very rough control (weak acid)

STRIPPINGSTRIPPING

• Mass transfer of a gas from the liquid phase to Mass transfer of a gas from the liquid phase to the gas phasethe gas phase

• TThe liquid is stripped with another gas (usually he liquid is stripped with another gas (usually air)air)

• Removal of ammonia, odorous gases, volatile Removal of ammonia, odorous gases, volatile organic compoundsorganic compounds

STRIPPINGSTRIPPING

• Nitrogen (ammonia) removalNitrogen (ammonia) removal

• aat high loaded biological WWTP or at low t high loaded biological WWTP or at low temperature there temperature there isis no significant nitrification no significant nitrification

• ammonia stripping is the most suitableammonia stripping is the most suitable

• rratio of ammoniaatio of ammonia (gas) (gas) -- ammonium depends ammonium depends on pHon pH

• NHNH44++ NH NH33 + H + H++

• between pH 10.5-11.0 mostly NHbetween pH 10.5-11.0 mostly NH33

STEPS OF NHSTEPS OF NH33 STRIPPING STRIPPING

1.1. pH control ( increase it to 10.5-11.0) pH control ( increase it to 10.5-11.0)

– – usually by limeusually by lime

2.2. aair stripping (intensive aeration of water)ir stripping (intensive aeration of water)

3.3. sedimentationsedimentation (calcium-carbonate + other (calcium-carbonate + other solids)solids)

STRIPPING OF VOLATILE STRIPPING OF VOLATILE COMPOUNDSCOMPOUNDS

• HydrocarbonsHydrocarbons

• Organic solventsOrganic solvents

• Chlorinated hydrocarbonsChlorinated hydrocarbons

• Aromatic compoundsAromatic compounds

STRIPPING OF HYDROGEN SULPHIDESTRIPPING OF HYDROGEN SULPHIDE

The problem of hydrogen sulphide – odour, corrosionThe problem of hydrogen sulphide – odour, corrosionStripping and oxidationStripping and oxidation

2H2H22S + OS + O22 2S + 2H 2S + 2H22OO

Other possibilities Other possibilities pH change (liming)pH change (liming)

Oxidation of HOxidation of H22S (nitrate feeding)S (nitrate feeding)

Conversion to non-soluble form (precipitation with Conversion to non-soluble form (precipitation with iron(III)-iron(III)-hydroxidehydroxide))

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Coagulant dose [mmol/l]

Res

idu

al d

isso

lved

su

lph

ide

con

cen

trat

ion

[m

g/l]

prefloc 1/2prefloc 3/1aluminium-sulphate 3/1prefloc 3/2

SULPHIDE REMOVALSULPHIDE REMOVAL DUE TO PRECIPITATION DUE TO PRECIPITATION WITH IRON-SALTSWITH IRON-SALTS

• Fe(III) ion reacts easily with sulphide ions - weakly water soluble compounds are formed

• dissolved sulphides can be precipitated rapidly in the presence of ferric salts (0.2-0.3 mmol/L)

• <5 mg/L sulphide in raw sewage - less than 0.1 mg/L after treatment• precipitation is not significant in case of aluminium salt

ADSORPTIONADSORPTION

• Adsorption is the physical and/or chemical Adsorption is the physical and/or chemical process in which a compound is accumulated process in which a compound is accumulated at an interface between phasesat an interface between phases ( (solid-liquid solid-liquid interfaceinterface))

• AdsorbateAdsorbate:: the substance being removed from the substance being removed from the liquid phase to the interfacethe liquid phase to the interface

• AdsorbentAdsorbent:: the the solid phase on which the solid phase on which the accumulation occursaccumulation occurs

ADSORPTIONADSORPTION

• Ion exchange adsorption = ions of a given species are Ion exchange adsorption = ions of a given species are displaced from an insoluble exchange material by displaced from an insoluble exchange material by ions of a different species in solution - softeningions of a different species in solution - softening– Ion change on natural matters (zeolite) – softening, Ion change on natural matters (zeolite) – softening,

ammonia removalammonia removal– Ion change on ion exchange resin (synthetic Ion change on ion exchange resin (synthetic

aluminosilicates, phenolic polymers)aluminosilicates, phenolic polymers)

• Adsorption on activated carbonAdsorption on activated carbon– PACPAC– GAC adsorbersGAC adsorbers

ADSORPTION ON ACTIVATED CARBONADSORPTION ON ACTIVATED CARBON

Activated carbon is able to remove dissolved organic substances Activated carbon is able to remove dissolved organic substances from water directly. The problem is that activated carbon is not from water directly. The problem is that activated carbon is not specific for pollutants, so during the activated carbon adsorption specific for pollutants, so during the activated carbon adsorption a lot of natural, non-pollutant type organic matters will be a lot of natural, non-pollutant type organic matters will be removed as well. The activated carbon adsorption is almost the removed as well. The activated carbon adsorption is almost the only process for removal of organic micropollutants from water.only process for removal of organic micropollutants from water.  The activated carbon is applied in two forms: powdered The activated carbon is applied in two forms: powdered activated carbon activated carbon = PAC = PAC (one time use) and granular activated (one time use) and granular activated carbon carbon = GAC = GAC (usable till saturation of adsorbent). The granular (usable till saturation of adsorbent). The granular activated carbon has higher specific organic matter removal activated carbon has higher specific organic matter removal capacity than powdered activated carbon. Although the capacity than powdered activated carbon. Although the powdered activated carbon is cheaper than granular, for long powdered activated carbon is cheaper than granular, for long time, permanent applying the granular activated carbon is more time, permanent applying the granular activated carbon is more economical.economical.

ACTIVATED ACTIVATED CARBONCARBON

chance of contact is high chance of contact is high more efficient adsorption more efficient adsorption widespreadwidespreadGACGAC

Water flows through the column Water flows through the column filled with granulated activated filled with granulated activated

carboncarbon

chance of contact is lower (in chance of contact is lower (in the water it is not possible to the water it is not possible to achieve as high activated carbon achieve as high activated carbon concentration as in GAC) - concentration as in GAC) - cheapercheaper

PACPAC

Activated carbon powder is Activated carbon powder is mixed into the water mixed into the water

•granulated – filled into a granulated – filled into a towertower•powdered – mixed into the powdered – mixed into the waterwater

CHEMICAL CHEMICAL WASTEWATER TREATMENTWASTEWATER TREATMENT

Definition of chemical wastewater treatment:Definition of chemical wastewater treatment: WIDER SENSE:WIDER SENSE:treatment of wastewaters with chemical methods treatment of wastewaters with chemical methods

• chemical coagulationchemical coagulation• chemical precipitation (removal of P and heavy metals)chemical precipitation (removal of P and heavy metals)• chemical disinfectionchemical disinfection• advanced oxidation processesadvanced oxidation processes• ion exchangeion exchange• chemical neutralizationchemical neutralization

MORE SPECIFIC:MORE SPECIFIC:addition of Fe-, Al-, Ca-, Mg-salts with the aim of phosphorus or addition of Fe-, Al-, Ca-, Mg-salts with the aim of phosphorus or organic removalorganic removal

CHEMICAL PHOSPHORUS REMOVALCHEMICAL PHOSPHORUS REMOVAL

Phosphorus removal (chemical precipitation) Phosphorus removal (chemical precipitation) AlAl3+3+ + PO + PO

443-3- AlPOAlPO

44

= converting of dissolved P compounds to a low solubility metal = converting of dissolved P compounds to a low solubility metal phosphate (through use of a metal salt) phosphate (through use of a metal salt)

Precipitants:Precipitants:Aluminium saltsAluminium saltsIron saltsIron saltsLime Lime

CHEMICAL PRECIPITATION OF CHEMICAL PRECIPITATION OF PHOSPHORUSPHOSPHORUS

Precipitation chemicals precipitate the dissolved inorganic Precipitation chemicals precipitate the dissolved inorganic phosphates as insoluble compounds (to be more exact: compounds phosphates as insoluble compounds (to be more exact: compounds with small solubility)with small solubility)

At the same time metal-hydroxides are formed At the same time metal-hydroxides are formed jelly-like flocs which bind the precipitated metal phosphates jelly-like flocs which bind the precipitated metal phosphates and any other suspended substances in the water (coagulation-and any other suspended substances in the water (coagulation-flocculation) flocculation)

This also removes organically combined P, as the amount of This also removes organically combined P, as the amount of suspended matter is greatly reduced by chemical precipitationsuspended matter is greatly reduced by chemical precipitation

CHEMICAL PHOSPHORUS REMOVALCHEMICAL PHOSPHORUS REMOVAL

1. Phosphorus removal (chemical precipitation) Al3+ + PO4

3- AlPO4

2.2. Removal of organic matter (coagulation-flocculation)Removal of organic matter (coagulation-flocculation)AAll3+3+ aluminium-hydroxide aluminium-hydroxide

• Good coagulant: contacts suspended matters (mainly Good coagulant: contacts suspended matters (mainly organics) of wastewater rapidly and stronglyorganics) of wastewater rapidly and strongly

• Organics are originally mainly in colloidOrganics are originally mainly in colloidalal form – do form – do not settle well – settling characteristics can be not settle well – settling characteristics can be improved due to coagulation-flocculationimproved due to coagulation-flocculation

Coagulation:Coagulation:destabilization of the colloidal particlesdestabilization of the colloidal particles

Flocculation:Flocculation:increase the size of flocsincrease the size of flocs

CHEMICAL TREATMENTCHEMICAL TREATMENT

· as the only treatment process as the only treatment process • primary (direct) precipitationprimary (direct) precipitation

· or in combination with biological treatment processes or in combination with biological treatment processes • pre-precipitationpre-precipitation • simultaneous precipitationsimultaneous precipitation• post-precipitationpost-precipitation

significant part of the organic pollutants is connected to suspended solids significant part of the organic pollutants is connected to suspended solids increasing of their removal efficiency in the primary settling tank results increasing of their removal efficiency in the primary settling tank results

low organic pollutant load in the activated sludge processeslow organic pollutant load in the activated sludge processes

CHEMICAL PHOSPHORUS REMOVALCHEMICAL PHOSPHORUS REMOVAL

Addition of calciumAddition of calcium• Usually in the form of limeUsually in the form of lime (Ca(OH) (Ca(OH)22))• Reacts with the natural bicarbonate alkalinity to precipitate Reacts with the natural bicarbonate alkalinity to precipitate

CaCOCaCO33

• As pH increases beyond 10, excess Ca ions react with the As pH increases beyond 10, excess Ca ions react with the phosphate to precipitate hydroxylapatitephosphate to precipitate hydroxylapatite

10 Ca10 Ca2+2+ + 6 PO + 6 PO443-3- + 2 OH + 2 OH-- Ca Ca1010(PO(PO44))66(OH)(OH)22

• pH has to be adjusted back before biological treatmentpH has to be adjusted back before biological treatment• No simultaneous P removal can be appliedNo simultaneous P removal can be applied

CHEMICAL PHOSPHORUS REMOVALCHEMICAL PHOSPHORUS REMOVAL

Addition of aluminium or ironAddition of aluminium or ironAlAl3+3+ + H + HnnPOPO44

3-n3-n AlPO AlPO44 + nH + nH++

FeFe3+3+ + H + HnnPOPO443-n3-n FePO FePO44 + nH + nH++

• 1 mole aluminium or iron ion will precipitate 1 mole of phosphate1 mole aluminium or iron ion will precipitate 1 mole of phosphate• Many competing reactionsMany competing reactions (the above ratio never occurs) (the above ratio never occurs)• We can not estimate the required dosage based on stoichiometryWe can not estimate the required dosage based on stoichiometry• Dosages established based on bench-scale testsDosages established based on bench-scale tests• Solubility of AlPOSolubility of AlPO44 is the smallest around pH = 6 is the smallest around pH = 6• Solubility of FePOSolubility of FePO44 is the smallest around pH = 5 is the smallest around pH = 5

PRECIPITANT ADDITIONPRECIPITANT ADDITION

PRE-PRECIPITATIONPRE-PRECIPITATION

15 perc

FlokkulátorHomokfogóRács

20 perc

Előlepítő

3 hFémsó

Eleveniszapos medence

Utóülepítő

2 h 3 h

screen grit chamber sedimentation activated sludge basin

sedimentation flocculator

metal saltmin min

BOD removal BOD removal 90% 90%

TP removal > 90%TP removal > 90%

PRE-PRECIPITATIONPRE-PRECIPITATION

Direct precipitation followed by a biological Direct precipitation followed by a biological treatment stagetreatment stage

Introduced to biological treatment plants to Introduced to biological treatment plants to reduce the loading to the biological stagereduce the loading to the biological stage

Reduction in energy consumption and in Reduction in energy consumption and in hydraulic retention timehydraulic retention time

SIMULTANEOUS PRECIPITATIONSIMULTANEOUS PRECIPITATION

20 perc

Homokfogó Előlepítő

Fémsó3 h

Eleveniszapos medence Utóülepítő

5 h 3 h

Rácsscreen grit chamber sedimentation activated sludge basin sedimentation

metal salt

min

BOD removal: 90%BOD removal: 90%

TP removal: 75-90%TP removal: 75-90%

SIMULTANEOUS PRECIPITATIONSIMULTANEOUS PRECIPITATION

Phosphorus is chemically precipitated at the same Phosphorus is chemically precipitated at the same time as biological treatment in an activated sludge time as biological treatment in an activated sludge processprocess

The biological stage also serves as a flocculation The biological stage also serves as a flocculation tank, with both the biological and chemical sludge tank, with both the biological and chemical sludge being separated in a subsequent stagebeing separated in a subsequent stage

Results 1 mg/L TPResults 1 mg/L TP

POST-POST-PRECIPITATIONPRECIPITATION

Homokfogó

20 perc

Rács Előlepítő

3 h

Ülepítő

2 h4 h

Utólepítő

3 h15 perc

Fémsó

Eleveniszapos medence

Vegyszerbekeverő

Flokkulátorscreen grit chamber sedimentationactivated sludge

basin sedimentation

metal salt 20 min

sedimentation

10 min

coagulation tank and flocculator

BOD removal BOD removal 90% 90%

TP removal > 95%TP removal > 95%

POST-POST-PRECIPITATIONPRECIPITATION

Phosphorus is separated from biologically treated Phosphorus is separated from biologically treated water in a separate post-treatment stagewater in a separate post-treatment stage

TP below 0.5 mg/LTP below 0.5 mg/L

COAGULATION-FLOCCULATION COAGULATION-FLOCCULATION LABORATORY JAR TESTSLABORATORY JAR TESTS

• to compare the to compare the efficiency of efficiency of different different coagulants coagulants

• to determine to determine optimal dosageoptimal dosage

1-litre glass cylinders with Kemira's flocculator device 1-litre glass cylinders with Kemira's flocculator device

TP REMOVAL TP REMOVAL

0

2

4

6

8

10

12

14

16

0 10 20 30 40 50 60 70 80 90 100 110 120

Metal dose [mg Me3+/l]

TP

[mg/

l]

Prefloc

Bopac

FeCl3

Al2(SO4)3

RESIDUAL CODRESIDUAL CODCRCR CONCENTRATIONS CONCENTRATIONS

VS. COAGULANT DOSAGEVS. COAGULANT DOSAGE

0

100

200

300

400

500

600

0 10 20 30 40 50 60 70 80 90 100 110 120

Metal dose [mg Me3+/l]

CO

DC

r [m

g/l]

Prefloc

Bopac

FeCl3

Al2(SO4)3

dissolved CODCr :

227-405 mg/l

50-85% of the total organic matter