G. Seintis, I. Ntzoura, A Vlysidis, A Vlyssides* School of Chemical - - PowerPoint PPT Presentation

• G. Seintis, I. Ntzoura, A Vlysidis, A Vlyssides*

School of Chemical Engineering National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens, Greece

6th International Conference on Sustainable Solid Waste Management, Naxos Island, Greece, 13–16 June 2018

Contents

• Introduction
• Materials & Methods
• Results & Discussion
• Conclusions

Aim

• Simultaneous nitrification‐denitrification in one stage
• Anoxic conditions
• Mathematical modelling
• Assimilation of carbon & nitrogen under reducing

conditions

Introduction

Nitrification‐Denitrification process Nitrification: Aerobic step 2NH4

++3O2→2NO2 ‐+4H++2H2O (Nitritation step)

AOB (Nitrosomas spp.) 2NO2

‐+O2→2NO3 ‐(Nitratation step)

NOB (Nitrobacter spp.) Denitrification: Anoxic step NO3

‐→NO2 ‐→NO→N2O→N2

Introduction

Alternative nitrification‐denitrification processes

• Sharon
• Anammox
• Canon
• OLAND
• NOx
• Aerobic deammonification

External carbon source Less COD consumed No COD needed

Introduction

SBR (Sequencing Batch Reactor)

• Activated sludge system
• Semi‐continuous feeding
• Biological oxidation and sedimentation are performed in

the same tank The process phases are time‐distinctive and not space‐ distinctive

Introduction

Phases

• Idle
• Feeding (+ mixing)
• Aeration (+ mixing)
• Settling
• Decanting

Introduction

Combination of anaerobic digestion and SBR

• The semicontinuous feeding provides control of ORP

conditions

• Possible

changes in treating conditions, in the characteristics of the influent and/or in the requirements

• f the quality of the effluent can be easily tackled
• High removal of COD (97%) & TN (98%)

Materials & Methods

• Location: TASTYFOODS.SA
• Combination of anaerobic‐aerobic reactors in series

UASB  SBR

• SBR

Working volume~935 m3 SRT 15 d Inflow 9‐12 m3/h. 3 8‐hour cycles

• Phase duration

Feeding ~ 30‐50 min Aeration 240‐305 min Mixing 15‐30 min Settling 150‐180 min Decanting ~ 45‐60 min. Controlling parameter of aeration time: DO End of aeration DO>2.5 mg/L.

Materials & Methods

Duration 21 8h cycles Sampling Inlet End of Aeration Sludge removal Effluent Analytical Methods DO pH tCOD sCOD TKN NH4+‐N NO3‐‐N TSS VSS

Results & Discussion

Parameter pH TSS (mg/L) VSS (mg/L) sCOD (mg/L) tCOD (mg/L) TKN (mg/L) NH4

+

(mg/L) NO3

‐

(mg/L) Inlet 6.99 878 595 934 1888 127 44 7.8

• Alkalinity: 625‐870 mg CaCO3/L
• VFA: 382.4 mg/L

Acetic acid: 107.3 mg/L Propionic acid: 135.2 mg/L Iso‐butyric: 78.7 mg/L Butyric: 38.6 mg/L Iso‐Valeric: 22.6 mg/L

88-122 mg/L NH4

+-N can be

• xidized

Results & Discussion

COD influent, effluent and % removal

00 05 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 00 500 1.000 1.500 2.000 2.500 3.000 3.500 4.000 4.500 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 % mg/L Ν tCODin tCODout sCODin sCODout %removal

Results & Discussion

Nitrogen fraction and % removal

00 10 20 30 40 50 60 70 80 90 100 00 20 40 60 80 100 120 140 160 180 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 % mg/L N NH4in Norg %NH4in %Removal

Results & Discussion

Nitrate throughout SBR cycles

00 02 04 06 08 10 12 14 16 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 mg/L N NO3in NO3aer NO3out

Results & Discussion

DO profile throughout an SBR cycle

0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2 10 20 30 40 50 60 70 mg/L N

DO 88.6%

Results & Discussion

pH throughout SBR cycles

0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00 5,50 6,00 6,50 7,00 7,50 8,00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 pHin pHTA pHout

Results & Discussion

Mean values of DO & % removal of COD throughout an SBR cycle

The different bioroutes for assimilating COD and TKN

Mathematical model

Autotrophic Bacteria (Nitrification) X1: Aerobic growth of (AOB)

• 1.5 ·

2 ·

,

• ·
• ·
• ·
• ·
• ·

,

• X2: Aerobic growth of Nitrite Oxidizing Bacteria (NOB)
• 2 ·

,

• ·
• ·
• ·
• ·
• ·

,

• X1=nitrosomonas, autotrophic bacteria

X2=nitrobacter, autotrophic bacteria X3, X4, X5=heterotrophic bacteria

The different bioroutes for assimilating COD and TKN

Mathematical model

Heterotrophic Bacteria (Denitrification) X3: Anoxic growth of nitrite reduction to nitrogen gas

• 0,375 0.125

0,5 ↑ 0.75 · 1,1375

,

• ·
• ,

·

• ·

, · ,

• X4: Anoxic growth of nitrate reduction to nitrogen gas

1,6

0,8 ↑ 2 · 1,6 1,2 ·

,

• ·
• ,

·

• ·

, · ,

• X5: Oxic growth of VFA (as Acetate) reduction to carbon dioxide

2 ·

2 ↑ 2 ·

,

• ·
• ·

, · ,

• X1=nitrosomonas, autotrophic bacteria

X2=nitrobacter, autotrophic bacteria X3, X4, X5=heterotrophic bacteria

The different bioroutes for assimilating COD and TKN

Mathematical model

Physic-chemical equilimbrium equations of the considered model

• ·
• ·
• ·
• ·
• ·
• Where [ ] = molar concentration

Total Inorganic Carbon : [TIC] = [CO2] +[HCO3

• ] +[CO3
• 2]

Charge balance: ∆ch = -[H+] +Kw/[H+] +[HCO3

• ] +2 [CO3
• 2]+[NO2
• ] +[NO3
• ]-[NH4

+]-Cz

X1=nitrosomonas, autotrophic bacteria X2=nitrobacter, autotrophic bacteria X3, X4, X5=heterotrophic bacteria

Conclusions

• Nitrification‐denitrification process in one stage
• UASB effluent

Reducing conditions Utilization of alkalinity  No need for COD oxidation Easily biodegradable organic carbon

• SBR system

Ideal option after anaerobic digestion of medium to high strength ammonium and carbon wastewater

• Successful assimilation of both the carbon and the nitrogen

The carbon assimilation is accomplished through the reduction step rather than the oxidation step Key factor: Low DO concentration (<1 mg/L)

Conclusions

• Adaptation to various organic loads
• Flexibility in altering the operating condition of

nitrification‐denitrification

• No need for external carbon source
• Working in reduction step  Aeration cost is reduced
• The availability of organic carbon through denitrification

reduces the risk of N2O emissions

Acknowledgement

The research was carried out in the framework of the research project "Control of Wastewater Treatment Plant from Potato Processing Industry " funded by TASTY FOODS SA

Thank you for your attention