| 1. |
- Ekholm, Jennifer, et al.
(author)
-
Full-scale aerobic granular sludge for municipal wastewater treatment – granule formation, microbial succession, and process performance
- 2022
-
In: Environmental Science: Water Research & Technology. - 2053-1419. ; :8, s. 3138-3154
-
Journal article (peer-reviewed)abstract
- Aerobic granular sludge (AGS) plants have gained growing interest and application due to their low energy demand, small footprint, and low operational costs. However, the fulfilment of strict discharge limits for nitrogen and phosphorus, vast seasonal temperature variations, and large peaks in influent flows may pose challenges to the implementation of AGS. Moreover, the knowledge about microbial community assembly and process performance under varying environmental conditions in full-scale reactors is still limited. In this study, the first implementation of the AGS process in the Nordic countries was assessed. In two full-scale AGS reactors with different seeding sludges, the start-up was associated with rapid changes in microbial community composition in both, but only successful granulation in one. As a consequence, the non-granulated reactor was eventually reseeded with biomass from the better granulated reactor. This resulted in a convergence of the microbial communities in the two reactors with the maintenance of stable sludge concentrations (6–8 g L−1) with large granules (50–80% with diameter >2 mm) and fast settling of biomass (SVI30/SVI10 of 0.9–1). Immigration from the influent wastewater was a minor factor affecting the microbial community once the granules had formed, while the seasonal variations in environmental factors were identified as important. Key guilds of AOB (Nitrosomonas), NOB (mainly Ca. Nitrotoga), PAOs (mainly Tetrasphaera), and GAOs (mainly Ca. Competibacter) varied considerably in abundance throughout the study period. After 15 months, stable organic matter, nitrogen, and phosphorus removal were attained with low effluent concentrations. During the start-up, the BOD7/N ratio, influent flow, and temperature were important factors influencing the performance of the AGS.
|
|
| 2. |
- Ekholm, Jennifer, 1992, et al.
(author)
-
Full-scale aerobic granular sludge for municipal wastewater treatment - granule formation, microbial succession, and process performance
- 2022
-
In: Environmental Science: Water Research and Technology. - : Royal Society of Chemistry (RSC). - 2053-1419 .- 2053-1400. ; 8:12, s. 3138-3154
-
Journal article (peer-reviewed)abstract
- Aerobic granular sludge (AGS) plants have gained growing interest and application due to their low energy demand, small footprint, and low operational costs. However, the fulfilment of strict discharge limits for nitrogen and phosphorus, vast seasonal temperature variations, and large peaks in influent flows may pose challenges to the implementation of AGS. Moreover, the knowledge about microbial community assembly and process performance under varying environmental conditions in full-scale reactors is still limited. In this study, the first implementation of the AGS process in the Nordic countries was assessed. In two full-scale AGS reactors with different seeding sludges, the start-up was associated with rapid changes in microbial community composition in both, but only successful granulation in one. As a consequence, the non-granulated reactor was eventually reseeded with biomass from the better granulated reactor. This resulted in a convergence of the microbial communities in the two reactors with the maintenance of stable sludge concentrations (6-8 g L-1) with large granules (50-80% with diameter >2 mm) and fast settling of biomass (SVI30/SVI10 of 0.9-1). Immigration from the influent wastewater was a minor factor affecting the microbial community once the granules had formed, while the seasonal variations in environmental factors were identified as important. Key guilds of AOB (Nitrosomonas), NOB (mainly Ca. Nitrotoga), PAOs (mainly Tetrasphaera), and GAOs (mainly Ca. Competibacter) varied considerably in abundance throughout the study period. After 15 months, stable organic matter, nitrogen, and phosphorus removal were attained with low effluent concentrations. During the start-up, the BOD7/N ratio, influent flow, and temperature were important factors influencing the performance of the AGS.
|
|
| 3. |
- Ekholm, Jennifer, 1992, et al.
(author)
-
Microbiome structure and function in parallel full-scale aerobic granular sludge and activated sludge processes
- 2024
-
In: Applied Microbiology and Biotechnology. - 1432-0614 .- 0175-7598. ; 108:1
-
Journal article (peer-reviewed)abstract
- Abstract: Aerobic granular sludge (AGS) and conventional activated sludge (CAS) are two different biological wastewater treatment processes. AGS consists of self-immobilised microorganisms that are transformed into spherical biofilms, whereas CAS has floccular sludge of lower density. In this study, we investigated the treatment performance and microbiome dynamics of two full-scale AGS reactors and a parallel CAS system at a municipal WWTP in Sweden. Both systems produced low effluent concentrations, with some fluctuations in phosphate and nitrate mainly due to variations in organic substrate availability. The microbial diversity was slightly higher in the AGS, with different dynamics in the microbiome over time. Seasonal periodicity was observed in both sludge types, with a larger shift in the CAS microbiome compared to the AGS. Groups important for reactor function, such as ammonia-oxidising bacteria (AOB), nitrite-oxidising bacteria (NOB), polyphosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs), followed similar trends in both systems, with higher relative abundances of PAOs and GAOs in the AGS. However, microbial composition and dynamics differed between the two systems at the genus level. For instance, among PAOs, Tetrasphaera was more prevalent in the AGS, while Dechloromonas was more common in the CAS. Among NOB, Ca. Nitrotoga had a higher relative abundance in the AGS, while Nitrospira was the main nitrifier in the CAS. Furthermore, network analysis revealed the clustering of the various genera within the guilds to modules with different temporal patterns, suggesting functional redundancy in both AGS and CAS. Key points: • Microbial community succession in parallel full-scale aerobic granular sludge (AGS) and conventional activated sludge (CAS) processes. • Higher periodicity in microbial community structure in CAS compared to in AGS. • Similar functional groups between AGS and CAS but different composition and dynamics at genus level. Graphical abstract: (Figure presented.).
|
|
| 4. |
- Bengtsson, Simon, 1977, et al.
(author)
-
A comparison of aerobic granular sludge with conventional and compact biological treatment technologies
- 2019
-
In: Environmental Technology (United Kingdom). - : Informa UK Limited. - 1479-487X .- 0959-3330. ; 40:21, s. 2769-2778
-
Journal article (peer-reviewed)abstract
- The aerobic granular sludge (AGS) technology is growing towards becoming a mature option for new municipal wastewater treatment plants and capacity extensions. A process based on AGS was compared to conventional activated sludge processes (with and without enhanced biological phosphorus removal), an integrated fixed-film activated sludge (IFAS) process and a membrane bioreactor (MBR) by estimating the land area demand (footprint), electricity demand and chemicals’ consumption. The process alternatives compared included pre-settling, sludge digestion and necessary post-treatment to achieve effluent concentrations of 8 mg/L nitrogen and 0.2 mg/L phosphorus at 7°C. The alternative based on AGS was estimated to have a 40–50% smaller footprint and 23% less electricity requirement than conventional activated sludge. In relation to the other compact treatment options IFAS and MBR, the AGS process had an estimated electricity usage that was 35–70% lower. This suggests a favourable potential for processes based on AGS although more available experience of AGS operation and performance at full scale is desired.
|
|
| 5. |
- Bengtsson, Simon, 1977, et al.
(author)
-
Treatment of municipal wastewater with aerobic granular sludge
- 2018
-
In: Critical Reviews in Environmental Science and Technology. - : Informa UK Limited. - 1064-3389 .- 1547-6537. ; 48:2, s. 119-166
-
Journal article (peer-reviewed)abstract
- Treatment of municipal wastewaters with aerobic granular sludge (AGS) has been extensively researched in the past decade and has now become a mature option for implementation. Aerobic granules are distinguished from activated sludge flocs through their larger size and more compact and spherical structure. Due to these properties, granules settle rapidly and can therefore contribute to compact treatment processes through high sludge concentrations and short settling times. In this review, the factors that promote granulation in treatment processes are identified and discussed and the experience of municipal wastewater treatment with AGS at laboratory-, pilot-, and full-scale are critically evaluated. The most important factors to promote granulation include exposing the biomass to relatively high concentrations of contaminants in sequencing batch reactors, promoting slow-growing microorganisms and applying a relatively short settling time. Enhanced biological phosphorus removal is preferably integrated with AGS and the large size of the granules makes simultaneous nitrification (at the surface of the granules) and denitrification (at the inner, anoxic parts) feasible. We propose directions for future research including further optimization of AGS to obtain stable and low effluent nutrient concentrations in line with increasingly stringent upcoming effluent demands.
|
|
| 6. |
- Ekholm, Jennifer, 1992, et al.
(author)
-
Case study of aerobic granular sludge and activated sludge—Energy usage, footprint, and nutrient removal
- 2023
-
In: Water Environment Research. - 1061-4303 .- 1554-7531. ; 95:8
-
Journal article (peer-reviewed)abstract
- This study demonstrates a comparison of energy usage, land footprint, and volumetric requirements of municipal wastewater treatment with aerobic granular sludge (AGS) and conventional activated sludge (CAS) at a full-scale wastewater treatment plant characterized by large fluctuations in nutrient loadings and temperature. The concentration of organic matter in the influent to the AGS was increased by means of hydrolysis and bypassing the pre-settler. Both treatment lines produced effluent concentrations below 5 mg BOD7 L−1, 10 mg TN L−1, and 1 mg TP L−1, by enhanced biological nitrogen- and phosphorus removal. In this case study, the averages of volumetric energy usage over 1 year were 0.22 ± 0.08 and 0.26 ± 0.07 kWh m−3 for the AGS and CAS, respectively. A larger difference was observed for the energy usage per reduced population equivalents (P.E.), which was on average 0.19 ± 0.08 kWh P.E.−1 for the AGS and 0.30 ± 0.08 kWh P.E.−1 for the CAS. However, both processes had the potential for decreased energy usage. Over 1 year, both processes showed similar fluctuations in energy usage, related to variations in loading, temperature, and DO. The AGS had a lower specific area, 0.3 m2 m−3 d−1, compared to 0.6 m2 m−3 d−1 of the CAS, and also a lower specific volume, 1.3 m3 m−3 d−1 compared to 2.0 m3 m−3 d−1. This study confirms that AGS at full-scale can be compact and still have comparable energy usage as CAS. Practitioner Points: Full-scale case study comparison of aerobic granular sludge (AGS) and conventional activated sludge (CAS), operated in parallel. AGS had 50 % lower footprint compared to CAS. Energy usage was lower in the AGS, but both processes had potential to improve the energy usage efficiency. Both processes showed low average effluent concentrations.
|
|
| 7. |
- Ekholm, Jennifer, 1992, et al.
(author)
-
Influence of decreasing temperature on aerobic granular sludge - microbial community dynamics and treatment performance
- 2024
-
In: Bioresource Technology Reports. - 2589-014X. ; 25
-
Journal article (peer-reviewed)abstract
- Municipal wastewater in temperate climates is characterized by seasonal temperature changes. Temperature is a determining factor for biological processes, but the impact of gradually decreasing temperature on aerobic granular sludge (AGS) has been largely unexplored. In this study, the influence of decreasing temperature from 20 °C to 6 °C on AGS was investigated at rates of 0.5 and 1 °C per week. Temperature was a major driver for microbial community change, where the community response could be divided into three main subclusters. Strains within the guilds of ammonium- and nitrite-oxidising bacteria (AOB and NOB) as well as polyphosphate- and glycogen-accumulating organisms (PAOs and GAOs) grouped in different subclusters, indicating variable responses among and between the guilds. The phosphorous removal rate was sufficient for complete removal at all temperatures, presumably due to functional redundancy within the PAOs. The nitrification rate was, however, seriously impaired below 13 °C, despite diversity within AOB and NOB.
|
|
