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Granular Sludge Session Flash presentations

In document IWA Biofilms 2020 (Sider 44-56)

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Granular Sludge Session

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Anammox Granule Enlargement by Heterogenous Granule Self-assembly

Wang, W.* and Wang, Y.*

**State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China, +86 (21)65984275 Keywords: Color; Granular sludge; Heterogeneity

Summary of key findings

Here, we propose a novel anammox granule enlargement mechanism by the self-assembly of

heterogenous anammox granules. Two different colors of anammox granules, dark-red granules (DR- Granules) and bright-red granules (BR-Granules) were found in an expanded granular sludge bed (EGSB) reactor. These two heterogenous granules were not isolated but were assembled into granules with a larger DR-Granule in the center and many smaller BR-Granules aggregated on the surface, increasing the overall granular size. Their physiochemical characteristics in terms of extracellular polymeric substances (EPS), adherence, rheological properties, and microbial compositions, were identified and compared to elucidate the interaction between the different color granules.

Background and relevance

Sludge granules are compact and dense aggregates (diameter larger than 200 μm) and formed through self-immobilization of microorganisms (Liu et al., 2009). Granular sludge technology has several advantages over dispersed sludge technology for sustainable wastewater treatment. These include excellent settleability, high biomass concentration, small footprint, great capacity to withstand high loadings, and high nutrient removal efficiency. Although great efforts have been made to investigate granulation mechanisms, no consensus has as yet been achieved, and the exact formation mechanism is still a mystery. Specifically, the process of granular size evolution is rarely mentioned or simply referred to as granule formation, even though it is an important part of the granule life cycle.

Granular sludge is a broadly spherical aggregate with different diameters (0.2–25 mm) (Zhu et al., 2018), and there are no two identical granules inside a reactor in terms of size, color, shape, etc. The heterogeneity among granules is very useful for investigation of some properties of granules. In the EGSB reactor used in this study, two colors of heterogenous anammox granules were found: DR- Granules and BR-Granules. These two types of granules were assembled in structures characterized by a larger DR-Granule in the center with many smaller BR-Granules aggregated on the surface. To understand the formation of these special anammox granules, the differences in EPS, adherence, rheological properties, and microbial compositions between the two heterogenous colors of anammox granules were analyzed and compared. Finally, a heterogenous anammox granule self-assembly mechanism was proposed to explain the enlargement of these anammox granules.To the best of our knowledge, the color segregation of anammox granules in the same reactor and the self-assembly of heterogenous anammox granules to enlarge granular size have not been reported previously.

Understanding the self-assembly mechanism by which the granular size increases will augment existing knowledge of granular size evolution, aid in understanding of the granulation process, and provide theoretical and engineering bases for the practical application of anammox granular techniques.

Results

Numerous special anammox granules were also observed in which many smaller BR-Granules adhered to the surface of a bigger DR-Granule that formed a core; this combination displayed a cauliflower-like surface (Fig. 1.1a–c). Furthermore, some large BR-Granules were observed which broke easily when touched and contained small DR core inside (Fig. 1.1d–f). Most of the DR-Granules

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had a compact structure with a lower ash content (12.9 ± 4.1%), while most of the BR -Granules had a fluffy structure and a higher ash content (14.6 ± 1. 9%; p = 0.46).

In DR-EPS, the concentrations of proteins, polysaccharides, humic acids, and DNA were 72.8 ± 12.8, 30.7 ± 1.7, 23.3 ± 9.0, and 10.4 ± 1.4 mg/g VSS, respectively; while those in BR -EPS were 129.8 ± 15.1, 74.1 ± 14.0, 53.7 ± 5.0, and 20.3 ± 1.9 mg/g VSS, respectively ( Fig. 1.2a). Thus, the total EPS concentration was 92% higher in BR-EPS than in DR-EPS (263.8 ± 12.6 vs. 137.2 ± 13.1 mg/g VSS;

p = 0.0002). The α-helix/(β-sheet and random coil) value of DR-EPS was 0.32 ± 0.03, which was lower than that of BR-EPS (0.62 ± 0.12; Fig. 1.2b and c; p = 0.015). A lower α-helix/(β-sheet and random coil) ratio corresponds to a looser protein structure, Therefore, the proteins in DR-EPS thus had a looser structure that exposed the inner hydrophobic functional groups and thus intensified the interactions between functional groups and promoted aggregation.

Adhesion properties were revealed using a quartz crystal microbalance technique with dissipation monitoring technique. Results found thet the anammox microbes from BR-Granules were more viscous than those from DR-Granules and formed a more rigid and compact adhered layer on the gold- coated sensor surface (Fig. 1.3a–c). Rheological measurements showed that the storage modulus (G′) of DR-Granules was 23.1 ± 0.7 kPa, which was much higher than that of BR -DR-Granules, 10.2 ± 0.6 kPa (p <

0.001; Fig. 1.3d–f). The yield stress (τc) of DR-Granules was also significantly higher than that of BR-Granules (932.5 ± 37.7 and 488.6 ± 72.3 Pa, respectively; p < 0.001). Therefore, the DR-BR-Granules had higher mechanical intensity than the BR-Granules. High-throughput sequencing found that the

BR-Granules had a higher relative abundance of total anammox bacteria than the DR-Granules (81.8 ± 5.3% vs. 71.2 ± 4.3%; p = 0.056), while the DR-Granules had a higher relative abundance of Ca.

Kuenenia (2.9 ± 0.4% vs. 0 .4 ± 0.1%; p = 0.0003; Fig. 1.4), which are nitrite K-strategy bacteria and dominate at low substrate concentration. qPCR results further confirmed that the absolute abundance of total anammox bacteria in the BR-Granules was (4.0 ± 0.4) ×10 11 copies/g VSS, approximately 57% higher than that in the DR-Granules [(2.6 ± 0.3) ×10 11 copies/g VSS] (p = 0.009).

Discussion

Based on visual observation and analysis of the different properties of heterogenous granules, a novel anammox granule enlargement mechanism by heterogenous granule self-assembly is proposed (Fig.

1.5). Specifically, at the same hydraulic shear force in the same reactor, the DR-Granules with high granule intensity were bigger, and the BR-Granules with low granule intensity tended to be smaller (Fig. 1.5b and c). The smaller BR-Granules had a higher EPS concentration, more compact protein secondary structure, and higher adherence rate to the surface of the bigger DR-Granules (Figs. 1.2a and 1.3a–c). The initial adhesion of two anammox granules could also be the adhesion of one granule to an inert site on the surface of the other granule, similar to that happened in the inert nuclei model for anaerobic granulation (Lettinga et al., 1980). The surfaces of the DR-Granules have many adhesion sites (like the abiotic gold-coated sensor surface) such as calcium and magnesium deposits, to which the smaller BR-Granules adhere. Through frequent collision and information exchange, a large number of BR-Granules tightly adhere to the surface of a bigger DR-Granule (Fig. 1.1a–c) and then grow along the DR-Granule surface, forming larger new granules that appear bright red (Fig. 1.5d).

However, as these granules grow, their substrate diffusion resistance increases, leading to lower substrate availability in the granular core. Such a starvation scenario stimulates anammox bacteria to secrete more EPS, which further prevents substrate from spreading inward, thus favoring the growth of nitrite K-strategy Ca. Kuenenia in the inner dark-red part of the granule (Fig. 1.4b). The higher EPS concentration in BR-Granules causes their lower intensity (Fig. 1.3f). The self-assembled anammox granules with low intensity easily disintegrate under the shear force in the water (Fig. 1.5e), releasing their inner dark-red cores of larger anammox granules, and the outer bright-red layer reforms as smaller BR-Granules.

In addition to self-assembling granules with different colors, it is likely that anammox granules can grow by the self-assembly of other heterogenous granules, including granules with different sizes and shapes. However, because of the hydraulic shear force in the bioreactor, only tightly adhered self-

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assembling granules can maintain their structure. The granules observed in this study, which have a large core granule surrounded by many small granules, are one example of such a structure. Further, this heterogenous granule self-assembly enlargement mechanism might also apply to other kinds of sludge granules, but this needs further verification.

Figure 1.1 Micro-observations of anammox granules using a stereoscopic microscope. (a–c) Many small BR-Granules adhering on the surface of a large DR-Granule; (d–f) large BR-Granules broke easily when touched, revealing small DR-Granules inside.

Figure 1.2 Chemical composition (a) and second derivative resolution-enhanced curve-fitted amide I region (1700–1600 cm−1) for proteins from DR-EPS (b) and BR-EPS (c).

Figure 1.3 Adherence (a–c) and rheological properties (d–f) of DR-Granule and BR-Granule samples.

Figure 1.4 Microbial community composition of anammox granules with different colors (i.e., BR and DR) at the phylum (a) and genus (b) levels.

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Figure 1.5 Photographs of anammox granules (a–e) and proposed enlargement mechanism for anammox granule by self-assembly of heterogenous granules (f). (a) The separated anammox granules with two different colors; (b, c) the self-assembled anammox granules; (d) the mature self-assembling anammox granule appeared BR color; (e) the broken BR-Granule contained smaller DR-Granule inside.

References (not incluced in page count, but please keep to a reasonable length)

Lettinga, G.A.F.M., Van Velsen, A.F.M., Hobma, S.W., Dezeeuw, W. and Klapwijk, A. (1980) Use of the upflow sludge blanket (USB) reactor concept for biological wastewater-treatment, especially for anaerobic treatment, Biotechnology and Bioengineering, 22 (4), 699-734

Liu, X.W., Sheng, G.P. and Yu, H.Q. (2009) Physicochemical characteristics of microbial granules, Biotechnology Advances, 27 (6), 1061-1070

Zhu, G., Wang, S., Ma, B., Wang, X., Zhou, J., Zhao, S. and Liu, R. (2018) Anammox granular sludge in low-ammonium sewage treatment: not bigger size driving better performance, Water Research, 142, 147-158

Presenting Author Dr. Wang PhD candidate Tongji University

Is the presenting author an IWA Young Water Professional? Y/N N

Bio: PhD candidate in College of Environmental Science and Engineering, Tongji University, Shanghai, China. The main research direction is the new technology of bioautotrophic nitrogen removal technology.

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Impact of substrate concentration on granular fermentation for caproic acid production

Mariën, Q.*, Candry, P.*, Rabaey, K.*, Carvajal-Arroyo, J. M.*, Ganigué, R.*

* Center for Microbial Ecology and Technology (CMET), Ghent University, Coupure Links 653, 9000 Ghent, Belgium

Keywords: fermentative granules; caproic acid; substrate concentration.

Summary of key findings

Recently, our laboratory demonstrated the feasibility of high rate caproic acid production, up to 13.7 g·L-1·d-1 from a biorefinery sidestream, by chain elongating granular biofilms in an expanded granular sludge bed reactor. In this study, we investigated the effect of substrate concentration on this system as a crucial first step towards feedstock diversification. We observed improved aggregation and

granulation with decreasing substrate concentrations, leading to higher retained biomass concentrations.

Conversely, higher substrate concentrations led to larger granules. Additionally, we found that caproic acid product selectivity remained constant at 48 ± 3% with increasing substrate concentration, up until 50 gCOD·L-1, after which product toxicity exerted by high caproic acid concentrations shifted the selectivity towards butyric acid.

Background and relevance

Today’s increasing organic waste production poses a challenge for the conversion of liquid waste streams into added-value products beyond low-value methane. A suitable alternative has been suggested to be the production of medium chain carboxylic acids (MCCAs) via a microbial process called chain elongation. In this process, an electron donor – e.g. ethanol or lactic acid– is used to elongate acetic acid to butyric acid, which is in turn elongated to caproic acid. MCCAs, and in particular caproic acid (C6), have a multitude of applications as feed additives, antimicrobial compounds and can be utilised in production of fragrances, rubbers, dyes and pharmaceuticals (Angenent et al., 2016). Lactic acid chain elongation has been proposed as a suitable alternative to ethanol, due to its potential coupling with lactic acid production from carbohydrates, eliminating the need for exogeneous ethanol addition (Chen et al., 2017; Zhu et al., 2015).

One key limitation in these production systems are production rates, an issue that was raised early on in the new wave of MCCA-research of the 2010s (Agler et al., 2011). Granular sludge are self-

aggregating biofilms, offering retention of high biomass concentrations that in turn enable higher conversion rates. These have been applied in other wastewater treatment technologies, and have recently found their way to MCCA production (Carvajal-Arroyo et al., 2019; Roghair et al., 2016; Wu et al., 2021). Moreover, our group recently demonstrated the feasibility of C6 production using fermentative granular biofilms in an expanded granular sludge bed (EGSB) reactor, by achieving productivities up to 13.7 gC6·L-1·d-1 from a real biorefinery sidestream (Carvajal-Arroyo et al., 2019).

However, the potential of this system was only demonstrated with a single feedstock and little is known about its benefits for other differently concentrated streams such as wastewaters from the brewery, dairy and food processing industries. Here, we investigated the effect of substrate

concentration as a first step towards feedstock diversification for high rate granular C6 production.

Results

Reduced substrate concentrations were investigated by diluting solids-free thin stillage (total substrate concentration of 44.15 gCOD·L-1; total carbohydrate content of 19.76 g·L-1), to respectively 75%, 50%

and 25% of its substrate concentration and feeding it to an EGSB reactor. In terms of product

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spectrum, the C6 concentration in the effluent decreased from 4.35 ± 0.25 g·L-1 at 100% to 1.59 ± 0.27 g·L-1 at 25%. However, the overall C6 selectivty remained constant at 48 ± 3% and lower substrate concentrations resulted in higher conversion efficiencies (Figure 1.1). Lower substrate concentrations also consistently yielded the highest amounts of total biomass (combination of planktonic and granular) due to substantial growth of the granular bed (Figure 2.1). Illumina 16S rRNA sequencing revealed that the reactor community was largely dominated by OTU classified as Caproiciproducens (86.41% of granular and 79.11% of planktonic community) and the lactic acid producing Olsenella genus (7.3% of granular and 17.68% of planktonic community). Below 44.15 gCOD·L-1, granule size was not affected, with granular diameters between 2.3 and 3.7 mm. Noteworthy was the appearance of floccular biomass at 25% stillage feedstock (Figure 2.1).

In a second experiment, solids-free thin stillage was amended with D-glucose to respectively 110%, 125% and 200% of the original COD. At increased carbohydrate loading, butyric acid accumulated, eventually reaching up to similar concentrations as C6 (from 1.78 ± 0.20 g·L-1 at 100% to 4.03 ± 0.48 g·L-1 at 125%; C6 at 4.35 ± 0.49 g·L-1; Figure 1.1). This in turn resulted in a strong decrease in C6 product selectivity. Analysing granule size at increased carbohydrate loading was not possible due to granule instability during sampling, but granules were visually larger (diameter approximately up to 1 cm; Figure 2.1).

Discussion

In this study, we investigated the response of C6 producing granular biofilms to varying substrate concentrations as a proxy for its potential to convert different waste feedstocks, leading to three key observations: (i) reduced substrate concentrations do not affect selectivity and increase conversion efficiency, (ii) increased substrate concentrations reduce selectivity and reduce conversion efficiency, and (iii) increased substrate concentrations affect granule growth and size although mechanisms are unclear.

The constant selectivity and increased substrate conversion efficiencies at low substrate concentrations demonstrate that high COD concentrations are no prerequisite for C6 production in an EGSB. However, the low product concentrations may pose challenges for efficient product extraction. High substrate concentrations on the other hand do not lead to increased C6 concentrations, likely due to product toxicity. MCCAs exert toxicity due to their amphipathic structure, which allows insertion of the undissociated acids in the membrane and even migration followed by acidification of the cytoplasm.

Planktonic ethanol chain elongation microbiomes have been reported to be inhibited at undissociated C6 concentrations around 7.5 mM, which are comparable to those achieved in this study of 7.25 ± 0.85 mM (Ge et al., 2015). Other planktonic lactic acid chain elongation studies have achieved undissociated C6 concentrations ranging from 7.4 mM (Zhu et al., 2015) up to 17.2 mM (Duber et al., 2018). The use of a granular biofilm may impose additional diffusional limitations and increase product toxicity since high intra-granule C6 concentrations may limit further conversion and lead to lower bulk C6

concentrations. Overall, this implies in-situ product extraction may be necessary to maintain high selectivities.

The consistent observation of highest amounts of total biomass at lower substrate concentrations suggest that substrate limitation and/or starvation may have a positive impact on biomass aggregation and thus retention in the reactor, but the mechanism remains unclear. Granules in the 25% to 100%

periods were of similar size to those found by Carvajal-arroyo et al., but substantially larger than other fermentative granules earlier reported (Roghair et al., 2016; Tamis et al., 2015; Wu et al., 2021). The larger granules observed at higher substrate concentrations have not been reported before and their formation mechanism remains unclear.

Overall, this study demonstrates that chain elongation in EGSBs offers a strong tool for the valorisation of carbohydrate-rich streams and could be expanded towards more dilute and concentrated waste streams in combination with efficient in-situ product extraction.

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Figure 1.1 Carboxylic acid concentration (A), selectivity (B) and substrate conversion efficiency (C) in function of the substrate concentration.

Figure 2.1 Evolution of the granular bed throughout varying substrate concentrations. The blue line indicates the same reference height in each picture.

References

Agler, M. T., Wrenn, B. A., Zinder, S. H., & Angenent, L. T. (2011). Waste to bioproduct conversion with undefined mixed cultures: The carboxylate platform. Trends in Biotechnology, 29(2), 70–78.

Angenent, L. T., Richter, H., Buckel, W., Spirito, C. M., Steinbusch, K. J. J., Plugge, C. M., … Hamelers, H. V. M. (2016).

Chain Elongation with Reactor Microbiomes: Open-Culture Biotechnology to Produce Biochemicals. Environmental Science and Technology, 50(6), 2796–2810.

Carvajal-Arroyo, J. M., Candry, P., Andersen, S. J., Props, R., Ganigué, R., Seviour, T., & Rabaey, K. (2019). Granular fermentation enables high rate caproic acid production from solid-free thin stillage. Green Chemistry, 32, 1–35.

Chen, W. S., Strik, D. P. B. T. B., Buisman, C. J. N., & Kroeze, C. (2017). Production of Caproic Acid from Mixed Organic

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Waste: An Environmental Life Cycle Perspective. Environmental Science and Technology, 51(12), 7159–7168.

Duber, A., Jaroszynski, L., Zagrodnik, R., Chwialkowska, J., Juzwa, W., Ciesielski, S., & Oleskowicz-Popiel, P. (2018).

Exploiting the real wastewater potential for resource recovery-: N -caproate production from acid whey. Green Chemistry, 20(16), 3790–3803.

Ge, S., Usack, J. G., Spirito, C. M., & Angenent, L. T. (2015). Long-Term n-Caproic Acid Production from Yeast- Fermentation Beer in an Anaerobic Bioreactor with Continuous Product Extraction. Environmental Science and Technology, 49(13), 8012–8021.

Roghair, M., Strik, D. P. B. T. B., Steinbusch, K. J. J., Weusthuis, R. A., Bruins, M. E., & Buisman, C. J. N. (2016). Granular sludge formation and characterization in a chain elongation process. Process Biochemistry, 51(10), 1594–1598.

Tamis, J., Joosse, B. M., van Loosdrecht, M. C. M., & Kleerebezem, R. (2015). High-rate volatile fatty acid (VFA) production by a granular sludge process at low pH. Biotechnology and Bioengineering, 112(11), 2248–2255.

Wu, Q., Feng, X., Chen, Y., Liu, M., & Bao, X. (2021). Continuous medium chain carboxylic acids production from excess sludge by granular chain-elongation process. Journal of Hazardous Materials, 402(May 2020), 123471.

Zhu, X., Tao, Y., Liang, C., Li, X., Wei, N., Zhang, W., … Bo, T. (2015). The synthesis of n-caproate from lactate: A new efficient process for medium-chain carboxylates production. Scientific Reports, 5(January), 1–9.

Presenting Author

Ir. Quinten Mariën PhD candidate

Center for Microbial Ecology and Technology (CMET), Ghent University Is the presenting author an IWA Young Water Professional? Y/N (i.e. an IWA member under 35 years of age)

Bio: Quinten Mariën is a bioprocess engineer and PhD researcher. After graduating with a Master in bioscience engineering, specialised in chemistry and bioprocess technology, he obtained a PhD fellowship from the Flanders Research Foundation.

He is fascinated by the potential of microbial technology in resource recovery and valorization from liquid and gaseous waste streams. His PhD research at Ghent University (Belgium) focuses on the development of novel

biofilm reactor technologies for high-rate fermentation and carbon capture. In his off time, he enjoys nature, great food and the occasional good book.

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Conductivity based dynamic control of the anaerobic step in an EBPR AGS SBR treating dairy wastewater

F. De Vleeschauwer*, T. Dobbeleers*, M. Caluwe*, C. Copot**, J. Dries*

*Research group BioWAVE, Faculty of Applied Engineering, University of Antwerp, Campus Groenenborger, Groenenborgerlaan 171, 2020 Antwerp, Belgium, flinn.devleeschauwer@uantwerpen.be,

thomas.dobbeleers@uantwerpen.be, michel.caluwé@uantwerpen.be, jan.dries2@uantwerpen.be

** Research group Op3Mech, Faculty of Applied Engineering, University of Antwerp, Campus Groenenborger, Groenenborgerlaan 171, 2020 Antwerp, Belgium, cosmin.copot@uantwerpen.be

Keywords: Aerobic granular sludge (AGS), enhanced biological phosphorus removal (EBPR); dynamic control

Summary of key findings

This study investigated an aerobic granular sludge reactor (AGS) with dynamically controlled anaerobic and aerobic steps. The reactor was fed dairy wastewater and applied a conductivity based anaerobic control and an oxygen uptake rate (OUR) based aerobic control. A hybrid AGS was formed and retained (DV10, DV50 and DV90 respectively 105±5µm, 336.5 ± 5.6 µm and 672±27µm). The anaerobic control successfully ensured an optimal anaerobic DOC uptake (96±5%). The effluent COD and PO4-P were 29±8 mgO2/l and 0.71±0.53mgPO4-P. The COD and PO4-P removal efficiency were respectively 95.6±2.6% and 93.5±4.7%. The dynamic control strategy successfully controlled the anaerobic step duration and ensured an optimal anaerobic DOC uptake. This strategy could be used in industrial EBPR AGS SBR treatment systems to optimize the anaerobic step operation.

Background and relevance

Up to date, an increasing number of full-scale anaerobic/aerobic AGS sewage wastewater treatment plants have been commissioned while only a few full scale industrial anaerobic/aerobic AGS wastewater treatment plants have been reported. This difference can be explained by the difficulty of treating complex and variable wastewater such as industrial wastewater with AGS. For example aerobic COD leakage is a threat to anaerobic/aerobic AGS systems with a static anaerobic step and varying COD concentrations. A possible solution is the use of sensor guided dynamically controlled anaerobic/aerobic AGS systems.

De Vleeschauwer et al., (2019) reported the use of a conductivity based anaerobic control strategy to dynamically control the duration of the anaerobic step in an EBPR system fed with synthetic wastewater.

The anaerobic control strategy is based on the correlation between the anaerobic conductivity profile and the PO4-P concentration profile. The conductivity increases during the PO4-P release and stagnates once the PO4-P release terminates (Maurer and Gujer., 1995).

In the current study, we investigate the application of this novel conductivity based strategy on a lab scale SBR treating real industrial wastewater. The dairy wastewater selected had a COD of 896 ± 471mg/l, a COD/P ratio of 79.2±33 and a COD/N ratio of 19.1±8.3.

A lab-scale AGS SBR was operated with an anaerobic/aerobic strategy for 92 days. The anaerobic step duration was controlled using a conductivity sensor. The same strategy was used as reported in De Vleeschauwer et al., (2019).

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The MLSS, MLVSS, SVI5 and SVI30 were analysed according to the standard methods (APHA 1998). The COD, PO4-P, NH4-N, NO3-N and NO2-N was analysed using Hanna instruments® chemical test kits. The DOC was measured with a Sievers InnovOx® laboratory TOC analyser. Sludge particle size (DV50) was determined with a Master size 3000 particle size analyser (De Vleeschauwer et al., 2019).

The reactor was seeded with sludge form a municipal wastewater treatment plant operated in cycles with 8 steps; aerobic idle (30min), anaerobic (10min), anaerobic feed (flow dependent), anaerobic (dynamic), aerobic (dynamic), anoxic (60 min), settling (10 min) and discharge (5min).

Results

Throughout the 92 day study the influent COD varied from 263 mg/l to 2444 mg/l and was on average 896±471mg/l. The effluent COD and PO4-P remained low at respectively 29±8mg/l and 0.71±0.53mg/l. The COD and PO4-P removal efficiencies were 95.6±2.6% and 93.5±4.7%.

Figure 1.1 (a) typical observed in-situ measurement (day 86), (b) typical observed correlation between the conductivity slope and the PO4-P concentration during the anaerobic step (day 86).

Figure 1 (a) shows a typical in-situ measurement taken on day 86. In Figure 1 (b) the correlation between the PO4-P concentration and the conductivity slope is shown. When the conductivity slope decreased below the setpoint of 1.5 µS/cm.day the anaerobic step was terminated.

The anaerobic step of an EPBR AGS SBR treating dairy waste water was successfully controlled using the conductivity profile. The anaerobic step duration was elongated or shortened depending on the influent COD concentration. Almost complete anaerobic DOC uptake was observed, with an average value of 96±5%. A stable hybrid AGS sludge was formed and retained. The DV50 stabilized at 336.5 ±

5.6 µm.

Discussion

The dynamic control strategy reported by De Vleeschauwer et al (2019) was successfully applied on an EBPR AGS SBR treating dairy wastewater. Similar COD and PO4-P removal efficiencies were obtained as statically operated AGS SBR and conventional SBR systems treating dairy wastewater. (Arrojo et al 2004, Kushwaha et al., 2011 and Bumbac et al., 2015).

The anaerobic conductivity profile was very similar to the profile seen in an acetate fed AGS SBR (Kishida et al., 2008 and De Vleeschauwer et al.,2019). The more complex composition of dairy wastewater had little effect on the anaerobic conductivity profile. As with the acetate fed AGS the anaerobic strategy had a high efficiency of 96.5 % compared to 98.2 %.

References

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APHA, 1998. Standard Methods for the Examination of Water and Wastewater, 20th ed. American Health Association/American Water Works Association/Water Environment Federation, Washington DC, USA.

Arrojo, B., Mosquera-Corral, A., Garrido J.M., Méndez, R. 2004 Aerobic granulation with industrial wastewater in sequencing batch reactors. Water Research 38, 3389-3399.

Bumbac, C., Ionescu, I.A., Tiron, O., Badescu, V.R. 2015 Continuous ow aerobic granular sludge reactor for dairy wastewater treatment. Water Science and Technology 71 (3), 440-445.

De Vleeschauwer, F., Caluwé, M., Dobbeleers, T., Stes, H., Dockx, L., Kiekens, F., D'Aes, J., Copot, C., Dries, J. 2019.

Performance and stability of a dynamically controlled EBPR anaerobic/aerobic granular sludge reactor. Bioresource Technology, 280, 151-157.

Kishida, N., Tsuneda, S., Sakakibara, Y., Kim, H., Sudo, R. 2008 Real-time control strategy for simultaneous nitrogen and phosphorus removal using aerobic granular sludge. Water science and Technology 58, 445-450.

Kushwaha, J.P., Srivastava, V.C., Indra Deo Mall, I.D., An Overview of Various Technologies for the Treatment of Dairy Wastewaters 2011 Food Science and Nutrition, ISSN: 1040-8398 print/1549-7852 online DOI: 10.1080/10408391003663879.

Maurer, M., Gujer, W. 1995 Monitoring of microbial phosphate release in batch experiments using electric conductivity.

Water Research 29 (11), 2613-2617.

Presenting Author

Mr. De Vleeschauwer PhD student

Is the presenting author an IWA Young Water Professional?

(i.e. an IWA member under 35 years of age) No, an old IWA Water Professional

Bio: Flinn is a “not so young” PhD student. After graduating with a degree in industrial biochemistry he quickly found his way into the water research world without ever leaving it.

He started as a research assistant studying aerobic granular sludge systems treating industrial wastewaters. This was followed by an enriching career in the local water municipal as project team leader. Thereafter he found his way back to the academic world as a PhD student at the University of Antwerp studying the anaerobic dynamic control of anaerobic/aerobic granular sludge systems treating industrial wastewater.

Nearly coming to the end of his PhD, he is now looking forward to a challenging continuation of his research project.

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Granular Sludge Session

In document IWA Biofilms 2020 (Sider 44-56)