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Accelerated Startup of PN/A Biofilm in ZeeNAMMOX
TMwithout
92 Materials and methods
As can be seen from Figure 1, three lab-scale ZeeNAMMOXTM pilots were constructed to examine the impacts of the gas phase O2 management strategies and one full-scale ZeeNAMMOXTM is designed to verify the optimal conditions under field conditions. ZeeNAMMOXTM models were set up in Biowin and calibrated using the results from the lab-scale pilots. Refer to Table 1 for the main design and operational conditions for these pilots.
All these pilots were or will be seeded with nitrifying activated sludge only, which is readily available in most wastewater treatment plants. Seed sludge for ZeeNAMMOXTM is normally washed out of the system in a few days since there is no secondary clarifier for sludge return. Process air flow rate and oxyen level are measured or monitored to determine the oxygen transfer rate (OTR). Samples of feed and effluent are taken for the tests of NH4+-N, NO2--N, NO3--N, and other parameters, and the results are used to determined the key performance indicators (KPIs) such as ammonium oxidation rate (AOR) and total inorganic nitrogen removal rate (TINRR).
Figure 1. ZeeNAMMOXTM pilots (a & b) and model configuration in Biowin (c) Table 1 Main design and operational parameters of ZeeNAMMOXTM pilots
Parameter unit R1 R2 R3 Field Demo
Tank volume L 6.5 6.5 6.5 12,000
Membrane
surface area m2 0.25 0.25 0.25 1,920
Wastewater n/a Diluted
centrate Diluted
centrate Diluted
centrate centrate
Feed flow rate L/d ~16.0 ~18.7 ~17.6 12,000
Feed NH4+-N mgN/L ~167 ~167 ~167 1,000
Bulk T °C ~34 ~34.4 ~35.6 >30.0
Bulk pH n/a ~7.8 ~7.8 ~7.8 7-8
Bulk DO mg/L ~0.1 ~0.1 ~0.1 <0.5
M-inlet-O2 gO2/m2/d 14 23 30 14-30
Results and discussion
ZeeNAMMOX Effluent Centrate
(a)
(b)
(c)
93 Three lab-scale ZeeNAMMOXTM pilots were seeded with same nitrifying activated sludge from an on-site membrane bioreactor (MBR). The initial MLSS in the pilots after seeding were around 2.5 g/L.
After an overnight initial attachment with the pilots being operated in batch mode, the seed sludge in the bulk liquid was gradually washed out in several days after the pilots were changed into continuous mode with the main operational conditions shown in Table 1.
Startup period: The startup period was determined by the time to achieve stable TIN removal rate in each pilot. As can be seen from Figure 2, the startup periods of R1, R2, and R3 are around 50 days, 80 days and 110 days, respectively. To the best of my knowledge, a startup period of 50 days is the shortest time to establish a single PN/A biofilm without anammox inoculum. Since these pilots were operated at different oxygen mass rates in the inlet air (M-inlet-O2) while other operational conditions were quite similar, it can be concluded that the difference in startup periods was mainly resulted from the difference in M-inlet-O2. Since lower M-inlet-O2 results in shorter startup period, it is recommended to minimize the oxygen supply during startup in ZeeNAMMOXTM. The inhibition of oxygen at higher M-inlet-O2 must have delayed the accumulation of anammox in the biofilm.
Performance at steady state: the AOR, TINRR and the ratio of TINRR/AOR at stable state are also presented in Figure 2. It can be seen from Figure 2 that AOR increases with the increase in M-inlet-O2 within the range of 14 to 30 gO2/m2/d; however, TINRR reaches a peak within the same range of M-inlet-O2. Therefore, there should be an optimal M-inlet-O2 to maximize AOR and TINRR at the same time. M-inlet-O2 Higher than this optimal M-inlet-O2 might increase AOR, however, it might start to compromise the performance of TIN removal. It seems that the optimal M-inlet-O2 might be higher than 23 gO2/m2/d, since the TINRR/AOR ratio at this point is 0.98, which is still much higher than the theoretical ratio of 0.89 for PN/A process (Strous et al., 1998).
Figure 2. Startup periods and the performance at stable states at different oxygen supply rates
Simulation in Biowin: calibration and sentivity studies were carried out in Biowin. Figure 2 shows the dynamic simulation of the performance in R2. One of the most sensitive parameters is the maximum specific growth rate of anammox, which was reduced below the default value to match the startup period. In the case of R2, it was reduced from the default value of 0.2d-1 to 0.05d-1. It should be noted that the maximum specific growth rate should be treated as a lumped growth rate, which might have included the impacts from some operational conditions. Since lower maximum specific growth rates are used to match the performance, this might indicate the operational conditions were not ideal for anammox to reach its maximum growth rate. In other words, this supports that the startup period of ZeeNAMMOXTM can be greatly reduced by optimizing the operational conditions and anammox inoculum might not be that critical.
1 0.98
0.59
0 1 2 3 4 5 6
0 20 40 60 80 100 120
14 23 30
AOR, TINRR (gN/m2/d) and TINRR/AOR ratio
Startup period (d)
Oxygen supply rate in inlet air (gO2/m2/d)
Startup period AOR TINRR TINRR/AOR ratio
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Figure 3. Dynamic simulation in Biowin
References (not incluced in page count, but please keep to a reasonable length)
Coutts, D., Long, Z., Peeters, J., Houweling, D., DiPofi, M., 2020(a). Side Stream Treatment with Membrane Aerated Biofilm Reactors - no Carbon, no Alkalinity and no Bubbles. IWA World Water Congress & Exhibition 2020.
Coutts, D., Di Pofi, M., Baumgarten, S., Guglielmi, G., Peeters, J., Houweling, D., 2020(b). Side-Stream treatment with Membrane Aerated Biofilm Reactors – the Simple, Robust and Energy Efficient Path. IWA Nutrient Removal and Recovery Conference 1 - 3 September 2020, Helsinki, Finland
Dimitrova, I., Dabrowska, A., Ekstrom, S., 2020. Startup of a full-scale partial nitritation-anammox MBBR without inoculum at Klagshamn WWTP. Water Science & Technology (2020) 81.9: 2033-2042.
Klaus, S., Baumler, R., Rutherford, B., Thesing, G., Zhao, H., Bott, C., 2017. Startup of a partial nitritation-anammox MBBR and the implementation of pH-based aeration control. Water Environment Research 89(6): 500-508.
Strous, M., Heijnen, J.J., Kuenen, J.G., Jetten, M. S. M., 1998. The sequencing batch reactor as a powerful tool for the study of slowly growing anaerobic ammonium-oxidizing microorganisms. Appl Microbiol Biotechnol (1998) 50: 589-596.
Long, Z., Houweling, D., Ireland, J., Peeters, J., Coutts, D., and Reeve, M., 2020. NOB Suppression in a Single ZeeNAMMOXTM Biofilm with the Coexistence of AOB and Anammox. IWA Biofilms 2020 Virtual Conference.
Presenting Author Dr Long
SUEZ Water Technologies and Solutions
Is the presenting author an IWA Young Water Professional? Y/N (i.e. an IWA member under 35 years of age) N
Bio: Zebo Long, a senior researcher with Suez WTS based in Canada. Zebo has over 10 years of working experience with expertise in wastewater treatment process design, system simulation, and microbial characterization. As a key team member, Zebo has developed ZeeLung membrane aerated biofilm (ZeeLung MABR) technology, which is widely considered as a disruptive innovation due to its high energy efficiency, low footprint, and reliable performance. Currently, Zebo is focusing on the development of ZeeNAMMOX, an innovative application of ZeeLung MABR in side-stream nitrogen removal.
0 1 2 3 4 5 6
0 20 40 60 80 100 120
AOR & TINRR (gN/m2/d)
Time (d)
AOR-R2 AOR-simulation TINRR-R2 TINRR-simulation
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