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Yu C, Wang K, Zhang K, Liu R, Zheng P. Full-scale upgrade activated sludge to continuous-flow aerobic granular sludge: Implementing microaerobic-aerobic configuration with internal separators. Water Res 2024; 248:120870. [PMID: 38007885 DOI: 10.1016/j.watres.2023.120870] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2023] [Revised: 11/10/2023] [Accepted: 11/12/2023] [Indexed: 11/28/2023]
Abstract
Aerobic granular sludge (AGS) has been successfully used in sequencing batch reactors. However, their application to existing continuous-flow systems remains challenging. In this study, a novel microaerobic-aerobic configuration with internal separators was implemented in a full-scale municipal wastewater treatment facility with a nominal capacity of 2.5 × 104 m3 d-1. Sludge characteristics, pollutant removal and associated pathways, shifts in the microbial community, and underlying granulation mechanisms were investigated. Following a two-month operation period, the transition from flocculent-activated sludge to well-defined AGS with distinct boundaries and compact structures was successfully achieved. The average size of sludge increased from 31.9 to 138.5 μm, with granules larger than 200 μm constituting 28.9 % of the total sludge and SVI30 averaging 51.4 ± 8.2 mL g-1. The 95th percentile effluent COD, NH4+-N, and TN concentrations were 35.0, 1.2, and 13.3 mg L-1, respectively. The primary pathways for pollutant removal were identified as simultaneous nitrification, denitrification, and phosphorus removal within the microaerobic tanks. The enrichment of denitrifying phosphorus-accumulating organisms, including Hydrogenophaga, Accumulibacter, Azospira, Dechloromonas, and Pseudomonas, provides an essential microbial foundation. Furthermore, computational fluid dynamics modeling revealed that the incorporation of internal separators in aerobic tanks induced shifts in the flow pattern, transitioning from a single-circulation cell to multiple vortical cells. This alteration amplified the local velocity gradients, generating the required shear forces to drive granulation. Moreover, mass balance analysis revealed that the microaerobic and aerobic tanks operated under feast and famine conditions, respectively, creating a microbial selection pressure that favored granulation. This process eliminates the need for external clarifiers, resulting in a footprint reduction of 38.2 % and one-third energy savings for sludge reflux. This study offers valuable insights into the application of continuous-flow AGS to upgrade existing activated sludge systems with limited retrofitting requirements.
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Affiliation(s)
- Cheng Yu
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China
| | - Kaijun Wang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China.
| | - Kaiyuan Zhang
- Beijing Huayide Environmental Technology Co. Ltd., Beijing 100084, PR China
| | - Ruiyang Liu
- Beijing Huayide Environmental Technology Co. Ltd., Beijing 100084, PR China
| | - Pingping Zheng
- Beijing Huayide Environmental Technology Co. Ltd., Beijing 100084, PR China
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An Z, Wang J, Zhang X, Bott CB, Angelotti B, Brooks M, Wang ZW. Coupling physical selection with biological selection for the startup of a pilot-scale, continuous flow, aerobic granular sludge reactor without treatment interruption. Water Res X 2023; 19:100186. [PMID: 37332326 PMCID: PMC10276156 DOI: 10.1016/j.wroa.2023.100186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/17/2023] [Revised: 05/29/2023] [Accepted: 05/31/2023] [Indexed: 06/20/2023]
Abstract
This study removes two technical constraints for transitioning full-scale activated sludge infrastructure to continuous flow, aerobic granular sludge (AGS) facilities. The first of these is the loss of treatment capacity as a result of the rapid washout of flocculent sludge inventory and in turn the potential loss of nitrification during initial AGS reactor startup. The second is the physical selector design which currently is limited to either the complex sequencing batch reactor selection or sidestream hydrocyclones. Briefly, real wastewater data collected from this study suggested that by increasing the surface overflow rate (SOR) of an upflow clarifier to 10 m h - 1, the clarifier can be taken advantage of as a physical selector to separate flocculant sludge from AGS. Redirecting the physical selector underflow and overflow sludge to the feast and famine zones of a treatment train, respectively, can create a biological selection that not only promotes AGS formation but also safeguards the effluent quality throughout the AGS reactor startup period. This study provides a novel concept for economically implementing continuous flow AGS within existing full-scale, continuous flow treatment trains.
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Affiliation(s)
- Zhaohui An
- Department of Biological Systems Engineering, Virginia Tech, 1230 Washington St. SW, Blacksburg, VA 24061, USA
| | - Jiefu Wang
- Department of Biological Systems Engineering, Virginia Tech, 1230 Washington St. SW, Blacksburg, VA 24061, USA
| | - Xueyao Zhang
- Department of Biological Systems Engineering, Virginia Tech, 1230 Washington St. SW, Blacksburg, VA 24061, USA
| | - Charles B. Bott
- Hampton Roads Sanitation District, 1434 Air Rail Avenue, Virginia Beach, VA 23455, USA
| | - Bob Angelotti
- Upper Occoquan Service Authority, 14631 Compton Rd, Centreville, VA 20121, USA
| | - Matt Brooks
- Upper Occoquan Service Authority, 14631 Compton Rd, Centreville, VA 20121, USA
| | - Zhi-Wu Wang
- Department of Biological Systems Engineering, Virginia Tech, 1230 Washington St. SW, Blacksburg, VA 24061, USA
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Wan C, Fu L, Li Z, Liu X, Lin L, Wu C. Formation, application, and storage-reactivation of aerobic granular sludge: A review. J Environ Manage 2022; 323:116302. [PMID: 36150350 DOI: 10.1016/j.jenvman.2022.116302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 08/31/2022] [Accepted: 09/14/2022] [Indexed: 06/16/2023]
Abstract
It was an important discovery in wastewater treatment that the microorganisms in the traditional activated sludge can form aerobic granular sludge (AGS) by self-aggregation under appropriate water quality and operation conditions. With a typical three-dimensional spherical structure, AGS has high sludge-water separation efficiency, great treatment capacity, and strong tolerance to toxic and harmful substances, so it has been considered to be one of the most promising wastewater treatment technologies. This paper comprehensively reviewed AGS from multiple perspectives over the past two decades, including the culture conditions, granulation mechanisms, metabolic and structural stability, storage, and its diverse applications. Some important issues, such as the reproducibility of culture conditions and the structural and functional stability during application and storage, were also summarized, and the research prospects were put forward. The aggregation behavior of microorganisms in AGS was explained from the perspectives of physiology and ecology of complex populations. The storage of AGS is considered to have large commercial potential value with the increase of large-scale applications. The purpose of this paper is to provide a reference for the systematic and in-depth study on the sludge aerobic granulation process.
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Affiliation(s)
- Chunli Wan
- Department of Environmental Science and Engineering, Fudan University, Shanghai, 200438, China
| | - Liya Fu
- Research Center of Environmental Pollution Control Engineering Technology, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China
| | - Zhengwen Li
- Department of Environmental Science and Engineering, Fudan University, Shanghai, 200438, China
| | - Xiang Liu
- Department of Environmental Science and Engineering, Fudan University, Shanghai, 200438, China.
| | - Lin Lin
- Environmental Science and New Energy Technology Research Center, Tsinghua-Berkeley Shenzhen Institute, Tsinghua University, Shenzhen, 518055, China
| | - Changyong Wu
- Research Center of Environmental Pollution Control Engineering Technology, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
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Xu D, Li J, Liu J, Ma T. Rapid aerobic sludge granulation in an integrated oxidation ditch with two-zone clarifiers. Water Res 2020; 175:115704. [PMID: 32208174 DOI: 10.1016/j.watres.2020.115704] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 02/29/2020] [Accepted: 03/08/2020] [Indexed: 06/10/2023]
Abstract
Aerobic granular sludge (AGS) was rapidly cultivated in an integrated oxidation ditch with two-zone clarifiers by using a novel external sludge treatment and return mode to treat low concentrations of actual domestic sewage. The selective pressure created by the two-zone clarifiers can retain the well-settling granules and discharge light flocs with poor settleability. The granules stayed in the reactor, which induced bacterial attachment to the granules that acted as nuclei, while the discharged flocs can stimulate microorganisms to secrete large amounts of extracellular polymeric substances (EPS) under the external conditioning of CaCl2 and natural air drying. Then, this surplus sludge was returned to the reactor to create more small granules that combined with each other through the action of hydraulic shear forces to achieve rapid granulation. The results showed that AGS was formed successfully in the reactor on day 18, and after 51 days of continuous operation, the biomass concentration and settling ability were further improved (the mixed liquor suspended solids (MLSS) and sludge volume index at 5 min (SVI5) were stable at approximately 3500 mg/L and 40.0 mL/g, respectively). During the whole experimental period, the biological sludge activity was greatly improved, and the EPS and microbial community changed significantly, including an enrichment of microbes with EPS secretion and granule stabilization functions. The study results reveal that the pollutant removal efficiency improved after granulation. Furthermore, this approach required less energy and is eco-friendly for potential full-scale implementation.
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Affiliation(s)
- Dong Xu
- College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China; College of Geomatics and Municipal Engineering, Zhejiang University of Water Resources and Electric Power, Hangzhou, 310018, China
| | - Jun Li
- College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China.
| | - Jun Liu
- Department of Civil Engineering, Tongji University Zhejiang College, Jiaxing, 314051, China
| | - Ting Ma
- College of Environment, Zhejiang University of Technology, Hangzhou, 310014, China
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Kent TR, Bott CB, Wang ZW. State of the art of aerobic granulation in continuous flow bioreactors. Biotechnol Adv 2018; 36:1139-1166. [PMID: 29597030 DOI: 10.1016/j.biotechadv.2018.03.015] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2017] [Revised: 03/21/2018] [Accepted: 03/21/2018] [Indexed: 10/17/2022]
Abstract
In the wake of the success of aerobic granulation in sequential batch reactors (SBRs) for treating wastewater, attention is beginning to turn to continuous flow applications. This is a necessary step given the advantages of continuous flow treatment processes and the fact that the majority of full-scale wastewater treatment plants across the world are operated with aeration tanks and clarifiers in a continuous flow mode. As in SBRs, applying a selection pressure, based on differences in either settling velocity or the size of the biomass, is essential for successful granulation in continuous flow reactors (CFRs). CFRs employed for aerobic granulation come in multiple configurations, each with their own means of achieving such a selection pressure. Other factors, such as bioaugmentation and hydraulic shear force, also contribute to aerobic granulation to some extent. Besides the formation of aerobic granules, long-term stability of aerobic granules is also a critical issue to be addressed. Inorganic precipitation, special inocula, and various operational optimization strategies have been used to improve granule long-term structural integrity. Accumulated studies reviewed in this work demonstrate that aerobic granulation in CFRs is capable of removing a wide spectrum of contaminants and achieving properties generally comparable to those in SBRs. Despite the notable research progress made toward successful aerobic granulation in lab-scale CFRs, to the best of our knowledge, there are only three full-scale tests of the technique, two being seeded with anammox-supported aerobic granules and the other with conventional aerobic granules; two other process alternatives are currently in development. Application of settling- or size-based selection pressures and feast/famine conditions are especially difficult to implement to these and similar mainstream systems. Future research efforts needs to be focused on the optimization of the granule-to-floc ratio, enhancement of granule activity, improvement of long-term granule stability, and a better understanding of aerobic granulation mechanisms in CFRs, especially in full-scale applications.
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Affiliation(s)
- Timothy R Kent
- Occoquan Laboratory, Department of Civil and Environmental Engineering, Virginia Tech, United States
| | | | - Zhi-Wu Wang
- Occoquan Laboratory, Department of Civil and Environmental Engineering, Virginia Tech, United States.
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Zou J, Tao Y, Li J, Wu S, Ni Y. Cultivating aerobic granular sludge in a developed continuous-flow reactor with two-zone sedimentation tank treating real and low-strength wastewater. Bioresour Technol 2018; 247:776-783. [PMID: 30060413 DOI: 10.1016/j.biortech.2017.09.088] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 09/10/2017] [Accepted: 09/13/2017] [Indexed: 06/08/2023]
Abstract
A continuous-flow reactor with two-zone sedimentation tank (CFR-TST) was developed to evaluate the formation of aerobic granular sludge (AGS). Micropowder made of excess sludge was added for a while in the CFR-TST, and selection pressure associated with settling time was created by the two-zone sedimentation tank. To avoid AGS disintegration, an airlift system for sludge return was used. The results show that AGS (mean particle size of 105μm; sludge volume index of approximately 26mL/g) was formed successfully in the CFR-TST. The micropowder induced bacterial attachment by acting as nuclei. The two-zone sedimentation tank made the well settling granules (i.e., heavy sludge) always retained in the CFR and poorly settling flocs (i.e., light sludge) washed away. After granulation, the contents of extracellular polymeric substances and metal precipitations in sludge increased, and the microbial community changed obviously. Additionally, the effluent concentrations of CODCr and NH4+-N were relatively low after granulation.
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Affiliation(s)
- Jinte Zou
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Yaqiang Tao
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Jun Li
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China.
| | - Shuyun Wu
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Yongjiong Ni
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
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Wei W, Bai Y, Liu Y. Optimization of submerged depth of surface aerators for a carrousel oxidation ditch based on large eddy simulation with Smagorinsky model. Water Sci Technol 2016; 73:1608-1618. [PMID: 27054732 DOI: 10.2166/wst.2015.638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
This paper is concerned with the simulation and experimental study of hydraulic characteristics in a pilot Carrousel oxidation ditch for the optimization of submerged depth ratio of surface aerators. The simulation was based on the large eddy simulation with the Smagorinsky model, and the velocity was monitored in the ditches with an acoustic Doppler velocimeter method. Comparisons of the simulated velocities and experimental ones show a good agreement, which validates that the accuracy of this simulation is good. The best submerged depth ratio of 2/3 for surface aerators was obtained according to the analysis of the flow field structure, the ratio of gas and liquid in the bottom layer of a ditch, the average velocity of mixture and the flow region with a velocity easily causing sludge deposition under the four operation conditions with submerged depth ratios of 1/3, 1/2, 2/3 and 3/4 for surface aerators. The research result can provide a reference for the design of Carrousel oxidation ditches.
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Affiliation(s)
- Wenli Wei
- State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Area (Xi'an University of Technology), Xi'an, Shaanxi 710049, China E-mail: ;
| | - Yu Bai
- State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Area (Xi'an University of Technology), Xi'an, Shaanxi 710049, China E-mail: ;
| | - Yuling Liu
- State Key Laboratory Base of Eco-Hydraulic Engineering in Arid Area (Xi'an University of Technology), Xi'an, Shaanxi 710049, China E-mail: ;
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Liu YQ, Lan GH, Zeng P. Excessive precipitation of CaCO3 as aragonite in a continuous aerobic granular sludge reactor. Appl Microbiol Biotechnol 2015; 99:8225-34. [DOI: 10.1007/s00253-015-6727-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 05/21/2015] [Accepted: 05/25/2015] [Indexed: 10/23/2022]
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