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 + +3O 2 → 2NO 2 ‐ +4H + +2H 2 O (Nitritation step) 2NH 4 AOB ( Nitrosomas spp.) ‐ +O 2 → 2NO 3 ‐ (Nitratation step) 2NO 2 NOB ( Nitrobacter spp.) Denitrification : Anoxic step ‐ → NO 2 ‐ → NO → N 2 O → N 2 NO 3

Introduction Alternative nitrification ‐ denitrification processes External carbon source  Sharon  Anammox Less COD consumed  Canon  OLAND  NO x  Aerobic deammonification 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 of 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 m 3 SRT 15 d Inflow 9 ‐ 12 m 3 /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 Analytical Methods DO pH Sampling tCOD Inlet sCOD End of Aeration TKN Sludge removal NH4 + ‐ N Effluent NO3 ‐ ‐ N TSS VSS

Results & Discussion + ‐ TSS VSS sCOD tCOD TKN NH 4 NO 3 Parameter pH (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) Inlet 6.99 878 595 934 1888 127 44 7.8 Alkalinity : 625 ‐ 870 mg CaCO 3 /L 88-122 mg/L NH 4 + -N can be • oxidized 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

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

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

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

Results & Discussion DO 2 1,8 1,6 1,4 1,2 mg/L 1 0,8 0,6 88.6% 0,4 0,2 0 0 10 20 30 40 50 60 70 N DO profile throughout an SBR cycle

Results & Discussion 8,00 7,50 7,00 6,50 6,00 5,50 5,00 4,50 pHin 4,00 pHTA 3,50 pHout 3,00 2,50 2,00 1,50 1,00 0,50 0,00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 pH throughout SBR cycles

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

Mathematical model Autotrophic Bacteria (Nitrification) X 1 : Aerobic growth of (AOB) ��� �� � � � 1.5 · � � � � 2 · � � � � � � �� � ��� ��� � � ��� � ���� �� � � � � ��� � � �,��� � · ��� � �� � · ��� � ��� � · ��� � � � · � �� � �� � � ��� � ���� � �� � ��� � � · � ��,��� ��� � ��� � � ���� � � ��� � ��� � � ��� X 2 : Aerobic growth of Nitrite Oxidizing Bacteria (NOB) ��� �� � � � � � � � � 2 · � � �� � ��� ��� � �� � � �� � � ��� � � ��� � � �,��� � · · ��� � �� � ��� � ��� � � �� � � �� � � �� � � ��� � � � � ��� � · · � · � ��� � � � ��� � ��� � ��,��� � � � � ��� � � � ��� � � ��� The different bioroutes for assimilating COD and TKN � ��� X 1 =nitrosomonas, autotrophic bacteria X 2 =nitrobacter, autotrophic bacteria X 3 , X 4 , X 5 =heterotrophic bacteria

Mathematical model Heterotrophic Bacteria (Denitrification) X 3 : Anoxic growth of nitrite reduction to nitrogen gas 0,5 � � ↑ �0.75 · �� � � 1,1375 �� � � � 0,375 �� � ��� � � 0.125 � � � �� � � ��� � � �� � � ��� � � �,��� � � � ��� · · � · � ��,��� · � �,��� � ��,��� � � � � �� � � �� � � ��� � � ��� � ��� X 4 : Anoxic growth of nitrate reduction to nitrogen gas � � �� � ��� � 0,8 � � ↑ �2 · �� � � 1,6 �� � � 1,2 · � � � 1,6 �� � � ��� � � �� � � ��� � � �,��� � � � ��� · · � · � ��,��� · � �,��� � ��,��� � � � � �� � � �� � � ��� � � ��� � ��� X5: Oxic growth of VFA (as Acetate) reduction to carbon dioxide 2 �� � ↑ �2 · � � � 2 · � � � �� � ���� ��� � � The different bioroutes for assimilating COD and TKN � ��� � � �,��� � � � ��� · · � ��,��� · � �,��� � �� � � � � ��� � � ��� X 1 =nitrosomonas, autotrophic bacteria � ��� X 2 =nitrobacter, autotrophic bacteria X 3 , X 4 , X 5 =heterotrophic bacteria

Mathematical model Physic-chemical equilimbrium equations of the considered model � ��� �� � � � � � ��� � �� � · � � � �� � � �� � � · � � � � � � � ���� � �� � � ���� �� � ��� � ��� � � · � � � � � � � ��� � ��� � � ��� ��� � � � � � �� � �� � �� · � � �� � � � � ���� � �� � � ���� �� � � ��� � � ��� � � � ��� � � � �� � � � � � ��� � � · �� � � � � � � � � Where [ ] = molar concentration The different bioroutes for assimilating COD and TKN Total Inorganic Carbon : [TIC] = [CO 2 ] +[HCO 3 - ] +[CO 3 -2 ] X 1 =nitrosomonas, autotrophic bacteria Charge balance : ∆ ch = -[H + ] +K w /[H + ] +[HCO 3 - ] +2 [CO 3 -2 ]+[NO 2 - ] +[NO 3 - ]-[NH 4 + ]-C z X 2 =nitrobacter, autotrophic bacteria X 3 , X 4 , X 5 =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 N 2 O 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

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