biological plant sizing ing. alberto scaunich. existing plant (or available data flowrate existing...

BIOLOGICAL PLANT BIOLOGICAL PLANT SIZINGSIZING

Ing. Alberto ScaunichIng. Alberto Scaunich

EXISTING PLANTEXISTING PLANT (or available data flowrate(or available data flowrateand pollutants concentration)and pollutants concentration)

Generally are available data for:Flow Q [m3/d]Pollutant concentration c [mg/l]

Pollutant Load C [kg/d] = Q*c/1000

STATISTIC ELABORATION

- Number of values N

- Average Value M

- Standard Deviation

WHICHEVER

DISTRIBUTION

NORMAL

DISTRIBUTION

- Typical Values

M+

M+2

M+3

75%

91%

68.3%

95.4%

99,7%

EXISTING PLANTEXISTING PLANT (or available data flowrate(or available data flowrateand pollutants concentration)and pollutants concentration)

When are available a lot of data, it’s better to eliminate single data (only flow or only concentration).

Hence you proceed in statistic elaboration.At the end, when you have average values of flow and loads, calculate the

value ratio: average load (concentration)average flow

which generally is different from concentration average values and is more significant, representing the weighted average of concentrations.

NOTNOT EXISTING PLANTEXISTING PLANT

1. MUNICIPAL WASTE WATER

You have to refer your design to the SPECIFIC CONTRIBUTION PER CAPITA, which generally result prudential values.

2. INDUSTRIAL WASTE WATER

You have to refer your design to the available SPECIFIC CONTRIBUTION PER UNIT OF PRODUCTS, adopting some security factors.

POLLUTANTS BALANCE

In biological plant sizing the ratio COD/BOD and BOD/TKN (or In biological plant sizing the ratio COD/BOD and BOD/TKN (or COD/TKN) are very importantCOD/TKN) are very important

In Denitrification you need organic load to remove Nitrogen.In Denitrification you need organic load to remove Nitrogen.

assume:assume:

3 kgBOD/kg(N-NO3 kgBOD/kg(N-NO33))DENDEN sizing oxidationsizing oxidation

4 kgBOD/kg(N-NO4 kgBOD/kg(N-NO33))DENDEN sizing post-denitrificationsizing post-denitrification

(methanol requirements) (methanol requirements)

Calculate Pollutants balance for these following cases (to verify section Calculate Pollutants balance for these following cases (to verify section sizing):sizing):

M (BOD) + M(TKN)M (BOD) + M(TKN)M(BOD) + M+2M(BOD) + M+2(TKN) (TKN) M+2M+2BOD) + M(TKN)BOD) + M(TKN)

NITROGEN BALANCE

TKNTKNinin+(N-NO+(N-NO

22))inin+(N-NO+(N-NO33))inin = =

= TKN= TKNSEDSED+(N-NO+(N-NO

33))DENDEN+TKN+TKNoxox+TKN+TKN

outout+(N-NO+(N-NO22))outout+(N-NO+(N-NO

33))outout

Where:Where:

TKNTKNinin = inlet Nitrogen (organic ed ammonia)= inlet Nitrogen (organic ed ammonia)

(N-NO(N-NO22))inin = inlet Nitrogen (nitrite):= inlet Nitrogen (nitrite): generally absentgenerally absent

(N-NO(N-NO33))inin = inlet Nitrogen (nitrate):= inlet Nitrogen (nitrate): present only in industrial wastewaterpresent only in industrial wastewater

TKNTKNSEDSED = organic Nitrogen removed in primary sedimentation: 10÷15% TKN= organic Nitrogen removed in primary sedimentation: 10÷15% TKN inin TKNTKNinin(N-NO(N-NO33))DENDEN = nitrogen to remove by denitrification= nitrogen to remove by denitrification

TKNTKNoxox = TKN removed by = TKN removed by bacterial metabolism (5% BOD removed in bacterial metabolism (5% BOD removed in biological treatment = 0,05 (BODibiological treatment = 0,05 (BODin Den n Den – BOD– BODoutout))

TKNTKNoutout = outlet Nitrogen (organic ed ammonia) - assume: 1 mg/l = outlet Nitrogen (organic ed ammonia) - assume: 1 mg/l

(N-NO(N-NO22))outout = outlet Nitrogen (nitrite) - negligible= outlet Nitrogen (nitrite) - negligible

(N-NO(N-NO33))outout = outlet Nitrogen (nitrate) - project requirement(10÷15 mg/l)= outlet Nitrogen (nitrate) - project requirement(10÷15 mg/l)

Normally you can’t have in the same time significant values of (N-NHNormally you can’t have in the same time significant values of (N-NH33))outout and and (N-NO(N-NO33))outout

DENITRIFICATION DESIGN

DENITRIFICATION VELOCITY (municipal effluents)DENITRIFICATION VELOCITY (municipal effluents)

((DD))TT = ( = (DD))2020 * * T-20T-20

Where:Where:

((DD))T T [gN-NO3/kgVSS*d] = Denitrification velocity:actual operative conditions [gN-NO3/kgVSS*d] = Denitrification velocity:actual operative conditions (temperature = T); (temperature = T);

((DD))2020 [gN-NO3/kgVSS*d] = Denitrification velocity: max value at T = 20 °C, [gN-NO3/kgVSS*d] = Denitrification velocity: max value at T = 20 °C, without any limiting factor; without any limiting factor;

= Temperature correction coefficient (higher value, higher T dependence)= Temperature correction coefficient (higher value, higher T dependence)

Process parameter Symbol M.U. Value Reference

Max Denitrification velocity (D)20 g N-NO3/

(Kg VSS*d) 80÷100 Ekama – Beccari

Temperature correction

coefficient / 1,06÷1.08 Ekama - Beccari

DENITRIFICATION VELOCITYDENITRIFICATION VELOCITY

DENITRIFICATION

    INTERNAL CARBON

PRE-DEN Inizial velocity

PRE-DEN Average

vel.

POST-DEN Average

vel.   

VOCE Unità di misuraScaunich vecchio

Scaunich attuale

Forte influenza

T

Esercizio attuale

Debole influenza

T

Organic fraction SSV/SST 0,7 0,7 0,7 0,7 0,7

Temperature correction coefficient   1,12 1,065 1,200 1,080 1,030

Denitrification velocity a °C 20 gN-NO3/kgSSTxd 70,0 56,0 504,0 70,7 50,4

  a °C 18 gN-NO3/kgSSTxd 55,8 49,4 350,0 60,6 47,5

  a °C 16 gN-NO3/kgSSTxd 44,5 43,5 243,1 52,0 44,8

  a °C 14 gN-NO3/kgSSTxd 35,5 38,4 168,8 44,6 42,2

  a °C 12 gN-NO3/kgSSTxd 28,3 33,8 117,2 38,2 39,8

  a °C 10 gN-NO3/kgSSTxd 22,5 29,8 81,4 32,7 37,5

Denitrification velocity a °C 20 gN-NO3/kgSSVxd 100,0 80,0 720,0 101,0 72,0

  a °C 18 gN-NO3/kgSSVxd 79,7 70,5 500,0 86,6 67,9

  a °C 16 gN-NO3/kgSSVxd 63,6 62,2 347,2 74,2 64,0

  a °C 14 gN-NO3/kgSSVxd 50,7 54,8 241,1 63,6 60,3

  a °C 12 gN-NO3/kgSSVxd 40,4 48,3 167,4 54,6 56,8

  a °C 10 gN-NO3/kgSSVxd 32,2 42,6 116,3 46,8 53,6

DENITRIFICATION VOLUME CALCULATION

(N-NO(N-NO33))DENDEN

VV = -------------------= -------------------

((DD))TT * * X X

Where:Where:

V [mV [m33]] = = Minimum design Denitrification volume Minimum design Denitrification volume

T [°C]T [°C] = = Minimum design TemperatureMinimum design Temperature

(N-NO(N-NO33))DENDEN [kg N-NO [kg N-NO33/d] = nitrogen to remove by denitrification/d] = nitrogen to remove by denitrification

XX [kgSSV/m [kgSSV/m33]: = Volatile Suspended Solids concentration in biological basins ]: = Volatile Suspended Solids concentration in biological basins (Denitrification – Nitrification)(Denitrification – Nitrification)

NoteNote:: It’s opportune to assure a minimum residential time of 3÷4 h at the maximum flow, to It’s opportune to assure a minimum residential time of 3÷4 h at the maximum flow, to give to mixed liquor enough time to reduce its Ogive to mixed liquor enough time to reduce its O22 content (DO concentration of 0,5 content (DO concentration of 0,5

mg/l reduce denitrification efficiency to 10%) mg/l reduce denitrification efficiency to 10%)

MIXED LIQUOR TO RECYCLE CALCULATION

1000 * (N-NO1000 * (N-NO33))DENDEN

QQML ML = ------------------------- - Q= ------------------------- - QRR

24 * 24 * N-NON-NO3 out3 out

Where:Where:

QQML ML [m[m33/h] = flowrate of recirculated Mixed Liquor /h] = flowrate of recirculated Mixed Liquor

QQR R [m[m33/h] = return sludge flowrate/h] = return sludge flowrate

(N-NO(N-NO33))DENDEN [kg N-NO [kg N-NO33/d] = nitrogen to remove by denitrification/d] = nitrogen to remove by denitrification

N-NON-NO3 out3 out [g/m[g/m33] = concentration of nitrogen in outlet stream (design value) ] = concentration of nitrogen in outlet stream (design value)

10001000 = conversion factor (kg = conversion factor (kg g) g)

24 =24 = conversion factor (d conversion factor (d h) h)

MIXING - DENITRIFICATION

Above Above 8÷10 W/m8÷10 W/m33 energy density is required energy density is required (normal submersible mixers)(normal submersible mixers)

Mixer rotation velocity must be chosen as low as possible (< 700 rpm)Mixer rotation velocity must be chosen as low as possible (< 700 rpm)

OXIDATION DESIGN

PRELIMINARY SIZINGPRELIMINARY SIZING

BODBODinin

VV = --------------- = ---------------

XX * F/M * F/M

Where:Where:

BODBODinin [kgBOD/d] [kgBOD/d] = Inlet BOD, coming from Denitrification= Inlet BOD, coming from Denitrification

XX [kgSST/m [kgSST/m33] ] = Total Suspended Solids concentration in biological basins = Total Suspended Solids concentration in biological basins (Denitrification – Nitrification): Values: 4÷6 (Denitrification – Nitrification): Values: 4÷6

SSV/SSTSSV/SST = Organic fraction: typical = Organic fraction: typical = 0,7= 0,7

F/M [kgBOD/kgSST*d] = Ratio Food/Mass: F/M [kgBOD/kgSST*d] = Ratio Food/Mass: Typical valuesTypical values range range

- extended aeration- extended aeration 0,0750,075 (0,06÷0,09) (0,06÷0,09)

- nitrification - nitrification (according T)(according T) 0,15 0,15 (0,12÷0,18) (0,12÷0,18)

- carbon removal only (- carbon removal only ( =85-90%) =85-90%) 0,25 0,25 (0,2÷0,35) (0,2÷0,35)

OXIDATION DESIGN

NITRIFICATION VERIFINGNITRIFICATION VERIFING

Where:Where:

((nn))TT = Nitrification velocity: actual operative conditions (temperature = T [gTKN/kgSSV/d];= Nitrification velocity: actual operative conditions (temperature = T [gTKN/kgSSV/d];

((nn))2020 = Nitrification velocity: max value at T = 20 °C, without any limiting factor; = Nitrification velocity: max value at T = 20 °C, without any limiting factor;

[gTKN/kgSSV/d];[gTKN/kgSSV/d];

= Temperature correction coefficient;= Temperature correction coefficient;

KKTKNTKN, K, KOO = semisaturation constants, relating to TKN and DO [mg/l]; = semisaturation constants, relating to TKN and DO [mg/l];

TKN, O.D.= TKN and Oxygen concentrations in biological basins [mg/l]TKN, O.D.= TKN and Oxygen concentrations in biological basins [mg/l]

OXIDATION DESIGN

NITRIFICATION VERIFINGNITRIFICATION VERIFING

OXIDATION DESIGN

CALCULATIONCALCULATION OF NITRIFICANT OF NITRIFICANT

BACTERIA FRACTIONBACTERIA FRACTION

Where:Where:

y N y N = nitrificant bacteria cellular yield coefficient [kgSSV/kg/TKN]= nitrificant bacteria cellular yield coefficient [kgSSV/kg/TKN]

y y = heterotrophic= heterotrophic bacteria cellular yield coefficientbacteria cellular yield coefficient [gSSV/gBOD][gSSV/gBOD]

S0S0 = inlet organic matter [mg/l] = inlet organic matter [mg/l]

Se Se = outlet organic matter [mg/l]= outlet organic matter [mg/l]

TKN0 TKN0 = inlet TKN [mg/l]= inlet TKN [mg/l]

TKNe TKNe = outlet TKN [mg/l]= outlet TKN [mg/l]

y/yN = 4,72 (Bonomo, 2008)y/yN = 4,72 (Bonomo, 2008)

OXIDATION DESIGN

NITRIFICATION VOLUME CALCULATIONNITRIFICATION VOLUME CALCULATION

Where:Where:

x x == Total Suspended Solids concentration in biological basins [kgSST/m3] Total Suspended Solids concentration in biological basins [kgSST/m3]

XXNN = Total nitrificant bacteria in nitrification basins [kgSST]= Total nitrificant bacteria in nitrification basins [kgSST]

OXIDATION DESIGN

RETURN SLUDGE FLOWRATERETURN SLUDGE FLOWRATE

Where:Where:

xxrr = = Total Suspended Solids concentration in return sludge [kgSST/m3] Total Suspended Solids concentration in return sludge [kgSST/m3]

OXIDATION DESIGN

RETURN SLUDGE FLOWRATE – IMHOFF CONERETURN SLUDGE FLOWRATE – IMHOFF CONE

(Q + Q(Q + Qrr)V)Vaa = Q = Qrr V Vrr

QQrr V Vaa

-------------- -------------- = --------------- = ---------------

QQ V Vrr - V - V

aa

If VIf Vr r == 1 l/l1 l/l

QQrr V Vaa

-------------- -------------- = --------------- = ---------------

QQ 1 - V 1 - Vaa

OXIDATION DESIGN

RETURN SLUDGE FLOWRATE SVI (sludge volume index)RETURN SLUDGE FLOWRATE SVI (sludge volume index)

Where:Where:

x =x = Total Suspended Solids concentration in biological basins [g/l]Total Suspended Solids concentration in biological basins [g/l]

QQrr x x

-------------- -------------- = --------------- = ---------------

QQ 1000/SVI - x 1000/SVI - x

Imhoff cone – 30 min [ml/l] or [cc/l]

Imhoff Imhoff SVI = --------------- SVI = --------------- xx

OXIDATION DESIGN

EXCESS SLUDGE FLOWRATE CALCULATIONEXCESS SLUDGE FLOWRATE CALCULATION

OXIDATION DESIGN

ACTUAL OXYGEN REQUIREMENTS (AOR) & STANDARD OXYGEN ACTUAL OXYGEN REQUIREMENTS (AOR) & STANDARD OXYGEN REQUIREMENTS (SOR)REQUIREMENTS (SOR)

Where:Where:

a a = Carbon removal coefficient = 0,5 kgO2/kgBOD= Carbon removal coefficient = 0,5 kgO2/kgBOD

b b = Endogenous respiration coefficient = 0,08 kgO2/kgSST/d= Endogenous respiration coefficient = 0,08 kgO2/kgSST/d

N N da nitrificare da nitrificare = N to remove in nitrification [kgN-NH4/d]= N to remove in nitrification [kgN-NH4/d]

2,86 KgO2/KgN2,86 KgO2/KgNDENDEN = Oxygen recovery = Oxygen recovery

OXIDATION DESIGN

ACTUAL OXYGEN REQUIREMENTS (AOR) & STANDARD OXYGEN ACTUAL OXYGEN REQUIREMENTS (AOR) & STANDARD OXYGEN REQUIREMENTS (SOR)REQUIREMENTS (SOR)

Where:Where:

aa = rapporto tra il coefficiente di trasferimento relativo al liquido reale a 20°C e = rapporto tra il coefficiente di trasferimento relativo al liquido reale a 20°C e quello relativo alle condizioni standard, fissato pari a 0,70;quello relativo alle condizioni standard, fissato pari a 0,70;

bb = rapporto tra la concentrazione di ossigeno a saturazione nel liquido reale in = rapporto tra la concentrazione di ossigeno a saturazione nel liquido reale in condizioni di esercizio e quella in acqua pulita in condizioni di esercizio;condizioni di esercizio e quella in acqua pulita in condizioni di esercizio;

CCs,Ts,T = concentrazione di ossigeno a saturazione in acqua pulita alla temperatura di = concentrazione di ossigeno a saturazione in acqua pulita alla temperatura di esercizio T;esercizio T;

CCw,Tw,T = concentrazione di ossigeno nel liquido reale alle condizioni di esercizio, fissata = concentrazione di ossigeno nel liquido reale alle condizioni di esercizio, fissata pari a 2 mg/l;pari a 2 mg/l;

CCs,*s,* = concentrazione di saturazione in acqua pulita in condizioni standard (20 °C);= concentrazione di saturazione in acqua pulita in condizioni standard (20 °C);

T T = Temperatura nelle condizioni di esercizio= Temperatura nelle condizioni di esercizio

OXIDATION DESIGN

AIR DEMANDAIR DEMAND

Where:Where:

24 = days hours;24 = days hours;

0,28 = Kg O0,28 = Kg O22 / mc air in standard conditions (20°C – 0 m a.s.l.); / mc air in standard conditions (20°C – 0 m a.s.l.);

hh = transfer efficiency O = transfer efficiency O2 2 = 5% / m depth. = 5% / m depth.

SEDIMENTATION DESIGN

Hydraulic head Hydraulic head (mc/mqxh)(mc/mqxh)

CCii=Q/A=Q/A 0,20 – 0,300,20 – 0,30 - Q (mc/h), flowrate- Q (mc/h), flowrate

- A (mq), area- A (mq), area Solid load Solid load

(kg SST/mqxd)(kg SST/mqxd)Cs = G/ACs = G/A < 5 a Q< 5 a Q2424

<9 a Q<9 a Qmaxmax

- G (kgSST/d), solid - G (kgSST/d), solid flowrate = 2,5 Qr Xflowrate = 2,5 Qr X

- X (kgSST/mc), - X (kgSST/mc), activated sludge activated sludge concentrationconcentration

- Qr (mc/h), return - Qr (mc/h), return sludge flowrate = 1 – 1,5 sludge flowrate = 1 – 1,5 QQ2424

Height (m)Height (m) ≥≥3m3m

Bridge Bridge Suction bridgeSuction bridge

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WASTEWATER TREATMENT PLANT

PIATTELLI PER AERAZIONE AD ALTA PIATTELLI PER AERAZIONE AD ALTA EFFICIENZAEFFICIENZA

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OSSIDAZIONE E TUBAZIONI RICIRCOLOOSSIDAZIONE E TUBAZIONI RICIRCOLO

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OSSIDAZIONEOSSIDAZIONE

BIOLOGICAL TREATMENTS

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DENITRIFICAZIONE - OSSIDAZIONEDENITRIFICAZIONE - OSSIDAZIONE

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OSSIDAZIONE - OKIOSSIDAZIONE - OKI

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OSSIDAZIONE A BOLLE MEDIEOSSIDAZIONE A BOLLE MEDIE

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BIODISCHIBIODISCHI

BIOLOGICAL TREATMENTS

SEDIMENTAZIONESEDIMENTAZIONE

BIOLOGICAL TREATMENTS

SEDIMENTAZIONESEDIMENTAZIONE

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SEDIMENTAZIONE – CARROPONTE ASPIRATOSEDIMENTAZIONE – CARROPONTE ASPIRATO

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