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Environmental Protection by Aerobic Granular Sludge Process

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A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Environmental and Green Processes".

Deadline for manuscript submissions: closed (30 December 2022) | Viewed by 24936

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Dr. Yongqiang Liu

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Faculty of Engineering and Physical Sciences, University of Southampton, Southampton SO16 7QF, UK
Interests: biological wastewater treatment; aerobic granulation; membrane technology; LCA; thermochemical technology for resource recovery

Special Issue Information

This Special Issue is in memory of Prof Joo Hwa Tay for his significant contribution to the advancement of acerbic granule technology!

text

Dear Colleagues,

It is well accepted that, as an economically attractive and environmentally friendly technology, the aerobic granular sludge process (AGSP) has many advantages over the conventional activated sludge biological nutrient removal (CAS-BNR) system, including smaller footprint with higher treatment capacity, lower energy and operational cost, no chemical addition, better effluent quality, and higher tolerance to toxins and shock loadings. As the technology matures in the past fifteen years, more and more engineering application have been established. However, some fundamental questions still remain unanswered:

What is the best way to achieve a fast and stable granulation?
How to maximize granule stability under disturbance or harsh conditions?
How to improve the performance when toxins and/or recalcitrant pollutants are targeted using the AGSP technology?
How to facilitate resource recovery with aerobic granular sludge?
What are the key parameters for process design when scaling up the AGSP reactors?
How to model the AGSP system, especially in regard to pollutant removal kinetics?

To address these questions, more investigations into the granulation and pollutant removal mechanisms are in urgent need.

This Special Issue on “Environmental Protection by Aerobic Granular Sludge Process” aims to discuss novel advances in the development and study of process control, optimization, and scaling up for the AGSP. Topics include, but are not limited to:

Strategies for a fast and stable granulation process
Strategies to maintain granule stability and identification of key parameters
Strategies for stable nutrient removal and resource recovery
Process optimization for the removal of challenging pollutants with the AGSP
Process scaling up
Process modeling

Dr. Yongqiang Liu
Guest Editor

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Keywords

Environmental protection
Aerobic granular sludge process
Process control
Process optimization
Nutrient removal
Resource recovery
Scale up
Toxin removal
Persistent pollutants
Mechanisms

Published Papers (12 papers)

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Editorial

Jump to: Research, Review

5 pages, 165 KiB

Open AccessEditorial

Environmental Protection through Aerobic Granular Sludge Process

by Yong-Qiang Liu

Processes 2024, 12(2), 243; https://doi.org/10.3390/pr12020243 - 24 Jan 2024

Viewed by 1046

Abstract

Aerobic granular sludge (AGS) represents a significant advancement in wastewater treatment technology [...] Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

Research

Jump to: Editorial, Review

13 pages, 5226 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Effects of Nitrate Recycle on the Sludge Densification in Plug-Flow Bioreactors Fed with Real Domestic Wastewater

by Jie-Fu Wang, Zhao-Hui An, Xue-Yao Zhang, Bob Angelotti, Matt Brooks and Zhi-Wu Wang

Processes 2023, 11(7), 1876; https://doi.org/10.3390/pr11071876 - 22 Jun 2023

Viewed by 1250

Abstract

The impact of adding a modified Ludzack–Ettinger (MLE) configuration with Nitrate Recycle (NRCY) on continuous-flow aerobic granulation has yet to be explored. The potential negative effects of MLE on sludge densification include that: (1) bioflocs brought by NRCY could compete with granules in feast zones; and (2) carbon addition to anoxic zones could increase the system organic loading rates and lead to higher feast-to-famine ratios. Two pilot-scale plug flow reactor (PFR) systems fed with real domestic wastewater were set up onsite to test these hypotheses. The results showed that MLE configuration with NRCY could hinder the sludge granulation, but the hindrance could be alleviated by the NRCY location change which to some extent also compensates for the negative effect of higher feast-to-famine ratios due to carbon addition in MLE. This NRCY location change can be advantageous to drive sludge densification without a radical washout of the sludge inventory, and had no effects on the chemical oxygen demand (COD) and nitrogen removal efficiencies. The PFR pilot design for the MLE process with a modified NRCY location tested in this study could be developed as an alternative to hydrocyclones for full-scale, greenfield, continuous sludge densification applications. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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20 pages, 1939 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Feasibility Study of Applying Anaerobic Step-Feeding Mode for the Treatment of High-Strength Wastewater in Granular Sequencing Batch Reactors (GSBRs)

by Elsayed Mady, Jan Oleszkiewicz and Qiuyan Yuan

Processes 2023, 11(1), 75; https://doi.org/10.3390/pr11010075 - 28 Dec 2022

Viewed by 1679

Abstract

This study investigated the feasibility of applying an anaerobic step-feeding strategy to enhance the performance of granular sequencing batch reactors (GSBRs) in terms of operational stability of the cultivated mature granules and nutrient removal efficiencies. Two identical 5 L reactors were operated with a total cycle time of 8 h. GSBRs were operated with high-strength synthetic wastewater (COD = 1250 ± 43, ammonium (NH₄-N) = 115.2 ± 4.6, and orthophosphate (PO₄-P) = 17.02 ± 0.9 mg/L) for 360 days through three stages: (1) Cultivation, 125 days (>2.1 mm); (2) Maturation, 175 days (>3 mm); (3) alternate feed loading strategy for R2 only for 60 days (anaerobic step-feeding). The granulation process, the physical properties of the granules, the nutrients, and the substrate removal performance were recorded during the entire operational period. For the cultivation and maturation stages, both reactors followed the fast single feeding mode followed by anaerobic mixing, and the results indicated a strong correlation between R1 and R2 due to the same working conditions. During the cultivation stage, adopting high organic loading rate (OLR) at the reactor start-up did not accelerate the formation of granules. Removal efficiency of PO₄-P was less than 76% during the maturation period, while it exceeded 90% for COD, and was higher than 80% for NH₄-N without effect of nitrite or nitrate accumulations due to simultaneous nitrification–denitrification. After changing filling mode for R2 only, there was unexpected deterioration in the performance and a rapid disintegration of the matured granules (poor settleability) accompanied by poor effluent quality due to high content of suspended solids because of applying selection pressure of short settling time. Consequently, GSBRs operation under the effect of fast single feeding mode followed by anaerobic mixing favors stable long-term granule stability. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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17 pages, 2509 KiB

Open AccessArticle

The Dynamic Shift of Bacterial Communities in Hybrid Anaerobic Baffled Reactor (ABR)—Aerobic Granules Process for Berberine Pharmaceutical Wastewater Treatment

by Yan Wang, Yongqiang Liu, Juan Li, Ruirui Ma, Ping Zeng, Choon Aun Ng and Fenghua Liu

Processes 2022, 10(12), 2506; https://doi.org/10.3390/pr10122506 - 25 Nov 2022

Cited by 3 | Viewed by 1216

Abstract

Because of its anticancer, anti-inflammatory, and antibiotic properties, berberine has been used extensively in medication. The extensive production of berberine results in the generation of wastewater containing concentrated residual berberine. However, to date, limited related studies on the biological treatment of berberine wastewaters have been carried out. A lab-scale anaerobic baffled reactor (ABR)–aerobic granular sludge (AGS) process was developed for berberine removal from synthetic wastewater. The system showed effective removal of the berberine. In order to better understand the roles of the bacterial community, the ABR–aerobic granular sludge system was operated in the state with the highest BBR removal rate in this study. The bacterial community dynamics were studied using the 16S rDNA clone library. The results showed that the hybrid ABR-AGS process achieved 92.2% and 94.8% overall removals of berberine and COD, respectively. Bacterium was dominant species in ABR, while the CFB group bacteria and Betaproteobacteria were dominant species in AGS process. The uncultured bacterium clone B135, Bacillus endophyticus strain a125, uncultured bacterium mle1-42, uncultured bacterium clone OP10D15, and uncultured bacterium clone B21.29F54 in ABR, and uncultured bacterium clone F54, uncultured bacterium clone ZBAF1-105, uncultured bacterium clone SS-9, and uncultured bacterium clone B13 in AGS process were identified as functional species in the biodegradation of berberine and/or its metabolites. Both anaerobic and aerobic bacterial communities could adapt appropriately to different berberine selection pressures because the functional species’ identical functions ensured comparable pollutant removal performances. The information provided in this study may help with future research in gaining a better understanding of berberine biodegradation. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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20 pages, 2944 KiB

Open AccessFeature PaperArticle

Cultivation of Nitrifying and Nitrifying-Denitrifying Aerobic Granular Sludge for Sidestream Treatment of Anaerobically Digested Sludge Centrate

by Guillian Morgan and Rania Ahmed Hamza

Processes 2022, 10(9), 1687; https://doi.org/10.3390/pr10091687 - 25 Aug 2022

Viewed by 1926

Abstract

In this study, three 1.2-L aerobic granular sludge sequencing batch reactors (AGS-SBRs) were used to cultivate nitrifying and nitrifying-denitrifying granules (w/supplemental carbon) and investigate sidestream treatment of synthetic-centrate and real-centrate samples from Ashbridges Bay Treatment Plant (ABTP) in Toronto, Ontario, Canada. Results showed that although the cultivation of distinct granules was not observed in the nitrifying reactors, sludge volume index (SVI₃₀) values achieved while treating real and synthetic centrate were 72 ± 12 mL/g and 59 ± 11 mL/g (after day 14), respectively. Ammonia-nitrogen (NH₃-N) removal in the nitrifying SBRs were 93 ± 19% and 94 ± 16% for real and synthetic centrate, respectively. Granules with a distinct round structure were successfully formed in the nitrifying-denitrifying SBR, resulting in an SVI₃₀ of 52 ± 23 mL/g. NH₃-N, chemical oxygen demand (COD) and phosphorus (P) removal in the nitrifying-denitrifying SBR were 92 ± 9%, 94 ± 5%, and 81 ± 14% (7th to 114th day), respectively with a low nitrite (NO₂-N) and nitrate (NO₃-N) concentration in the effluent indicating simultaneous nitrification-denitrification (SND) activity. High nutrient removal efficiencies via the nitrification and SND pathways shows that AGS technology is a viable process for treating sidestreams generated in a WWTP. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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16 pages, 26647 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Phosphorus Removal from Aerobic Granular Sludge: Proliferation of Polyphosphate-Accumulating Organisms (PAOs) under Different Feeding Strategies

by Oliver Terna Iorhemen, Sandra Ukaigwe, Hongyu Dang and Yang Liu

Processes 2022, 10(7), 1399; https://doi.org/10.3390/pr10071399 - 18 Jul 2022

Cited by 7 | Viewed by 2338

Abstract

Aerobic granular sludge (AGS) is known for high phosphorus removal from wastewaters, and phosphorus can be recovered from high phosphorus-containing waste sludge granules. This study aimed at determining the feeding strategy that provides the best performance in terms of the proliferation of polyphosphate-accumulating organisms (PAOs) and phosphorus removal. Using three AGS bioreactors, this study compared phosphorus removal and the proliferation dynamics of PAOs under three different feeding strategies: anaerobic slow feeding (R1), pulse feeding + anaerobic mixing (R2), and pulse feeding (R3). Results indicate that R1 and R2 achieved significantly higher phosphorus removal (97.6 ± 3% for R1 and 98.3 ± 1% for R2) than R3 (55 ± 11%). The anaerobic slow feeding procedure (R1) achieved the highest specific phosphorus release rate (SPRR) and specific phosphorus uptake rate (SPUR) as compared to the other two feeding conditions. 16S ribosomal ribonucleic acid (rRNA) gene sequencing assay of the microbial community for the three feeding strategies indicated that although the feeding strategy impacted reactor performance, it did not significantly alter the microbial community. The bacteria community composition maintained a similar degree of diversity. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the dominant bacterial phyla in the system. Dominant PAOs were from the class Betaproteobacteria and the genera Paracoccus and Thauera. Glycogen-accumulating organisms were significantly inhibited while other less-known bacteria such as Wandonia and Hyphomonas were observed in all three reactors. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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17 pages, 5632 KiB

Open AccessArticle

Reproducibility of Aerobic Granules in Treating Low-Strength and Low-C/N-Ratio Wastewater and Associated Microbial Community Structure

by Hongxing Zhang, Yong-Qiang Liu, Shichao Mao, Christain E. W. Steinberg, Wenyan Duan and Fangyuan Chen

Processes 2022, 10(3), 444; https://doi.org/10.3390/pr10030444 - 23 Feb 2022

Cited by 8 | Viewed by 1730

Abstract

Long-term stability of the aerobic granular sludge system is essentially based on the microbial community structure of the biomass. In this study, the physicochemical and microbial characteristics of sludge and wastewater treatment performance were investigated regarding formation, maturation, and long-term maintenance of granules in two parallel sequencing batch reactors (SBR), R1 and R2, under identical conditions. The aim was to explore the linkage between microbial community structure of the aerobic granules, their long-term stability, as well as the reproducibility of granulation and long-term stability. The two reactors were operated with a COD concentration of 400 mg/L and a chemical oxygen demand to nitrogen (COD/N) ratio of 4:1 under anoxic–oxic conditions. It was found that although SVI₃₀, sludge size, and distributions in R1 and R2 were different, aerobic granules were formed, and they maintained long-term stability in both reactors for 320 days, implying that a certain level of randomness of granulation does not affect the long-term stability and performance for COD and N removal. In addition, a significant reduction in the richness and diversity of microbial production was observed after the sludge was converted from inoculum or flocs to granules, but this did not negatively affect the performance of wastewater treatment. Among the predominant microbial species in aerobic granules, Zoogloea was identified as the most important bacteria present during the whole operation with the highest abundance, while Thauera was the important genus in the formation and maturation of the aerobic granules, but it cannot be maintained long-term due to the low food-to-microorganisms ratio (F/M) in the system. In addition, some species from Ohtaekwangia, Chryseobacterium, Taibaiella, and Tahibacter were found to proliferate strongly during long-term maintenance of aerobic granules. They may play an important role in the long-term stability of aerobic granules. These results demonstrate the reproducibility of granulation, the small influence of granulation on long-term stability, and the robustness of aerobic granulation for the removal of COD and N. Overall, our study contributes significantly to the understanding of microbial community structure for the long-term stability of aerobic granular sludge in the treatment of low-COD and low-COD/N-ratio wastewater in practice. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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14 pages, 1328 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Hydroxyapatite Precipitation and Accumulation in Granules and Its Effects on Activity and Stability of Partial Nitrifying Granules at Moderate and High Temperatures

by Yong-Qiang Liu and Simone Cinquepalmi

Processes 2021, 9(10), 1710; https://doi.org/10.3390/pr9101710 - 24 Sep 2021

Cited by 6 | Viewed by 1947

Abstract

Precipitation and accumulation of calcium phosphate in granular sludge has attracted research attention recently for phosphate removal and recovery from wastewater. This study investigated calcium phosphate accumulation from granulation stage to steady state by forming heterotrophic granules at different COD/N ratios at 21 and 32 °C, respectively, followed by the transformation of heterotrophic granules to partial nitrifying granules. It was found that mature granules accumulated around 60–80% minerals in granules, much higher than young granules with only around 30% ash contents. In addition, high temperature promoted co-precipitation of hydroxyapatite and calcite in granules with more calcite than hydroxyapatite and only 4.1% P content, while mainly hydroxyapatite was accumulated at the moderate temperature with 7.7% P content. The accumulation of minerals in granules at the high temperature with 75–80% ash content also led to the disintegration and instability of granules. Specific ammonium oxidation rates were reduced, as well, from day 58 to day 121 at both temperatures due to increased mineral contents. These results are meaningful to control or manipulate granular sludge for phosphorus removal and recovery by forming and accumulating hydroxyapatite in granules, as well as for the maintenance of microbial activities of granules. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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18 pages, 2156 KiB

Open AccessFeature PaperArticle

Effect of an Increased Particulate COD Load on the Aerobic Granular Sludge Process: A Full Scale Study

by Sara Toja Ortega, Mario Pronk and Merle K. de Kreuk

Processes 2021, 9(8), 1472; https://doi.org/10.3390/pr9081472 - 23 Aug 2021

Cited by 8 | Viewed by 2683

Abstract

High concentrations of particulate COD (pCOD) in the influent of aerobic granular sludge (AGS) systems are often associated to small granule diameter and a large fraction of flocculent sludge. At high particulate concentrations even granule stability and process performance might be compromised. However, pilot- or full-scale studies focusing on the effect of real wastewater particulates on AGS are scarce. This study describes a 3-month period of increased particulate loading at a municipal AGS wastewater treatment plant. The pCOD concentration of the influent increased from 0.5 g COD/L to 1.3 g COD/L, by adding an untreated slaughterhouse wastewater source to the influent. Sludge concentration, waste sludge production and COD and nutrient removal performance were monitored. Furthermore, to investigate how the sludge acclimatises to a higher influent particulate content, lipase and protease hydrolytic activities were studied, as well as the microbial community composition of the sludge. The composition of the granule bed and nutrient removal efficiency did not change considerably by the increased pCOD. Interestingly, the biomass-specific hydrolytic activities of the sludge did not increase during the test period either. However, already during normal operation the aerobic granules and flocs exhibited a hydrolytic potential that exceeded the influent concentrations of proteins and lipids. Microbial community analysis also revealed a high proportion of putative hydrolysing and fermenting organisms in the sludge, both during normal operation and during the test period. The results of this study highlight the robustness of the full-scale AGS process, which can bear a substantial increase in the influent pCOD concentration during an extended period. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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15 pages, 2222 KiB

Open AccessFeature PaperArticle

Effect of Salinity on Cr(VI) Bioremediation by Algal-Bacterial Aerobic Granular Sludge Treating Synthetic Wastewater

by Bach Van Nguyen, Xiaojing Yang, Shota Hirayama, Jixiang Wang, Ziwen Zhao, Zhongfang Lei, Kazuya Shimizu, Zhenya Zhang and Sinh Xuan Le

Processes 2021, 9(8), 1400; https://doi.org/10.3390/pr9081400 - 13 Aug 2021

Cited by 10 | Viewed by 2734

Abstract

Heavy metal-containing wastewater with high salinity challenges wastewater treatment plants (WWTPs) where the conventional activated sludge process is widely applied. Bioremediation has been proven to be an effective, economical, and eco-friendly technique to remove heavy metals from various wastewaters. The newly developed algal-bacterial aerobic granular sludge (AGS) has emerged as a promising biosorbent for treating wastewater containing heavy metals, especially Cr(VI). In this study, two identical cylindrical sequencing batch reactors (SBRs), i.e., R1 (Control) and R2 (with 1% additional salinity), were used to cultivate algal-bacterial AGS and then to evaluate the effect of salinity on the performance of the two SBRs. The results reflected that less filamentation and a rougher surface could be observed on algal-bacterial AGS when exposed to 1% salinity, which showed little influence on organics removal. However, the removals of total inorganic nitrogen (TIN) and total phosphorus (TP) were noticeably impacted at the 1% salinity condition, and were further decreased with the co-existence of 2 mg/L Cr(VI). The Cr(VI) removal efficiency, on the other hand, was 31–51% by R1 and 28–48% by R2, respectively, indicating that salinity exposure may slightly influence Cr(VI) bioremediation. In addition, salinity exposure stimulated more polysaccharides excretion from algal-bacterial AGS while Cr(VI) exposure promoted proteins excretion. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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12 pages, 4858 KiB

Open AccessFeature PaperArticle

Long-Term Stability of Nitrifying Granules in a Membrane Bioreactor without Hydraulic Selection Pressure

by Zhaohui An, Xueyao Zhang, Charles B. Bott and Zhi-Wu Wang

Processes 2021, 9(6), 1024; https://doi.org/10.3390/pr9061024 - 10 Jun 2021

Cited by 1 | Viewed by 2061

Abstract

To understand the long-term stability of nitrifying granules in a membrane bioreactor (GMBR), a membrane module was submerged in an airlift reactor to eliminate the hydraulic selection pressure that was believed to be the driving force of aerobic granulation. The long-term monitoring results showed that the structure of nitrifying granules could remain stable for 305 days in the GMBR without hydraulic selection pressure; however, the majority of the granule structure was actually inactive due to mass diffusion limitation. As a consequence, active biomass free of mass diffusion limitation only inhabited the top 60–80 µm layer of the nitrifying granules. There was a dynamic equilibrium between bioflocs and membrane, i.e., 25% of bioflocs attached on the membrane surface within the last nine days of the backwash cycle in synchronization with the emergence of a peak of soluble extracellular polymeric substances (sEPS), with a concentration of around 47 mg L⁻¹. Backwash can eventually detach and return these bioflocs to the bulk solution. However, the rate of membrane fouling did not change with and without the biofloc attachment. In a certain sense, the GMBR investigated in this study functioned in a similar fashion as an integrated fixed-film activated sludge membrane bioreactor and thus defeated the original purpose of GMBR development. The mass diffusion problem and sEPS production should be key areas of focus in future GMBR research. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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Review

Jump to: Editorial, Research

14 pages, 296 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Review on Digestibility of Aerobic Granular Sludge

by Mohamed S. Zaghloul, Asmaa M. Halbas, Rania A. Hamza and Elsayed Elbeshbishy

Processes 2023, 11(2), 326; https://doi.org/10.3390/pr11020326 - 19 Jan 2023

Cited by 4 | Viewed by 1893

Abstract

Full-scale wastewater treatment plants utilizing aerobic granular sludge technology are being built in many countries worldwide. As with all biological wastewater treatment plants, the produced waste biomass must be stabilized to protect the population, wildlife, and the environment. Digestion is usually used to break down the complex organics in the waste sludge; however, the digestibility of aerobic granular sludge still needs to be fully understood compared to the conventional activated sludge. This paper reviews the studies published on the digestibility of waste aerobic granular sludge to date. Studies comparing aerobic granular sludge and activated sludge in terms of composition, properties, and digestibility are highlighted. The impact of biological composition and physical properties on the digestibility of sludge is reviewed in terms of biomethane production and biodegradability. The effect of pre-treatment is also covered. Areas for future research are presented. Full article

(This article belongs to the Special Issue Environmental Protection by Aerobic Granular Sludge Process)

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