Characterizing the structure of aerobic granular sludge using ultra-high field magnetic resonance

Abstract Despite aerobic granular sludge wastewater treatment plants operating around the world, our understanding of internal granule structure and its relation to treatment efficiency remains limited. This can be attributed in part to the drawbacks of time-consuming, labor-intensive, and invasive microscopy protocols which effectively restrict samples sizes and may introduce artefacts. Time-domain nuclear magnetic resonance (NMR) allows non-invasive measurements which describe internal structural features of opaque, complex materials like biofilms. NMR was used to image aerobic granules collected from five full-scale wastewater treatment plants in the Netherlands and United States, as well as laboratory granules and control beads. T1 and T2 relaxation-weighted images reveal heterogeneous structures that include high- and low-density biofilm regions, water-like voids, and solid-like inclusions. Channels larger than approximately 50 μm and connected to the bulk fluid were not visible. Both cluster and ring-like structures were observed with each granule source having a characteristic structural type. These structures, and their NMR relaxation behavior, were stable over several months of storage. These observations reveal the complex structures within aerobic granules from a range of sources and highlight the need for non-invasive characterization methods like NMR to be applied in the ongoing effort to correlate structure and function.

Download Full-text

Performance Evaluation of Continuous Flow Aerobic Granular Sludge Configurations

Revista de Chimie ◽

10.37358/rc.19.1.6900 ◽

2019 ◽

Vol 70 (1) ◽

pp. 283-285

Author(s):

Elena Elisabeta Manea ◽

Costel Bumbac

Keyword(s):

Wastewater Treatment ◽

Continuous Flow ◽

High Efficiency ◽

Wastewater Treatment Plants ◽

Granular Sludge ◽

Synthetic Wastewater ◽

Aerobic Granular Sludge ◽

Batch Reactors ◽

Nutrients Removal ◽

Flow Configurations

Increasing the efficiency and capacity of existing wastewater treatment plants can be carried out by using intensive biological processes. One of the currently studied biological solutions consists in using aerobic granular sludge in order to achieve both organics and nutrients removal simultaneously in one tank and with high efficiency. Aerobic granular sludge is currently used at full scale in sequential batch reactors, research for identifying the optimal solutions for continuous flow systems being carried out worldwide. The paper summarizes the results obtained for two continuous flow configurations with aerobic granular sludge, in terms of organics and nutrients removal for synthetic wastewater in laboratory conditions. Both experimental setups led to wastewater treatment efficiencies, with values ranging between 80 and 99% for COD, 85 and 99% for BOD5, 52 and 98% for NH4+ and 5 to 87% for TP.

Download Full-text

Molecular mechanisms governing aerobic granular sludge processes

Water Practice & Technology ◽

10.2166/wpt.2015.032 ◽

2015 ◽

Vol 10 (2) ◽

pp. 277-281 ◽

Cited By ~ 1

Author(s):

Yan Zhou ◽

HuiJuan Xu ◽

Yu Liu

Keyword(s):

Wastewater Treatment ◽

Quorum Sensing ◽

Structural Stability ◽

Significant Role ◽

Molecular Mechanisms ◽

Granular Sludge ◽

Cellular Communication ◽

Aerobic Granular Sludge ◽

Aerobic Granules ◽

Aerobic Granulation

The aerobic granular sludge process is a promising technology for wastewater treatment. The formation and structure of aerobic granules are traditionally thought to depend highly on selection pressures, while the underlying molecular mechanisms are unclear. It is well known that bacteria coordinate their behavior using small signaling molecules, known as quorum sensing (QS). This paper is an attempt to provide updated information on QS mechanisms governing granular sludge processes. It is shown that QS-mediated cellular communication has a significant role throughout aerobic granulation, including granule development, structural stability and integrity maintenance. Such understanding is helpful for developing novel aerobic granular sludge processes.

Download Full-text

An Attempt to Develop Aerobic Granular Sludge in Continuous Airlift Reactors

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1025.265 ◽

2021 ◽

Vol 1025 ◽

pp. 265-272

Author(s):

Muhammad Syafiq Mohd Shafei ◽

Zulkifly Jemaat

Keyword(s):

Wastewater Treatment ◽

Operation Mode ◽

Treatment Plant ◽

Granular Sludge ◽

Cod Removal ◽

Aerobic Granular Sludge ◽

Organic Loading Rate ◽

Aerobic Granules ◽

Reactor Performance ◽

Airlift Reactors

Recent advancement on biological wastewater treatment is via granular sludge technology. It is widely known that, aerobic granular sludge has been developed in a batch operation since its discovery. Yet, most of the wastewater treatment plant (WWTP) is operated in continuous mode. Now, the real challenge is how to adopt the granular technology while maintaining present operation mode of WWTP. Thus, this study attempts to evaluate the feasibility of developing aerobic granular sludge in continuous airlift reactors feed with two different substrates, namely glucose and acetate. Two identical airlift reactors (6 L) were employed and operated at room temperature (30°C). Prior to the substrate feeding, both reactors were inoculated with seed sludge obtained from a palm oil mill anaerobic pond. One of the reactors was fed with 2000 mg COD L-1 of glucose (ALR1) and the other reactor with 2000 mg COD L-1 of acetate (ALR2). The hydraulic retention time (HRT) and organic loading rate (OLR) for both reactors were maintained at 4 days and between 0.2 to 0.5 kg m-3day-1 respectively. Dissolved oxygen was maintained between 5.0 and 6.0 mg O2L-1 and supplied by air compressor. The reactor performance was monitored based on COD removal. Aerobic granules developed throughout the study period was evaluated based on granules size and morphology, sludge volumetric index (SVI30) and SVI5/SVI30 ratio analysis. Results showed that ALR1 demonstrated the formation of filamentous-type aerobic granules with most of the SVI30 average at 100 to 190 mL g-1. Ratio SVI5/SVI30 analysis was evaluated at 0.2 and 0.5. The largest granules size obtained during the experiment was about 600 μm on day-136 and average granules size obtained at 200 to 400 μm. ALR1 able to achieve 95% COD removal. For ALR2, round shaped aerobic granules were developed with average SVI30 from 100 to 1000 mLg-1. SVI5/SVI30 analysis indicated an average ratio between 0.7 and 0.9. The average granules size was between 30 to 50 μm and the largest was 78 μm on day-60. 90% of COD removal efficiency was obtained in ALR2. In conclusion, ALR fed with acetate had indicated better aerobic granules characteristics as compared to glucose fed reactor. Furthermore, the study demonstrated that to develop aerobic granules in continuous reactors is feasible.

Download Full-text

Selection of slow growing organisms as a means for improving aerobic granular sludge stability

Water Science & Technology ◽

10.2166/wst.2004.0792 ◽

2004 ◽

Vol 49 (11-12) ◽

pp. 9-17 ◽

Cited By ~ 196

Author(s):

M.K. de Kreuk ◽

M.C.M. van Loosdrecht

Keyword(s):

Energy Efficient ◽

Laboratory Experiments ◽

Wastewater Treatment Plants ◽

Granular Sludge ◽

Aerobic Granular Sludge ◽

Aerobic Granules ◽

Low Oxygen ◽

Slow Growing ◽

Selection Of ◽

Oxygen Concentrations

Recently, several groups have showed the occurrence of aerobic granular sludge. The excellent settling characteristics of aerobic granular sludge allow the design of very compact wastewater treatment plants. In laboratory experiments, high oxygen concentrations were needed to obtain stable granulation. However, in order to obtain energy efficient aeration and good denitrification low oxygen concentrations would be required. From earlier research on biofilm morphology, it was learned that slow growing organisms influence the density and stability of biofilms positively. To decrease the growth rate of the organisms in the aerobic granules, easily degradable substrate (e.g. acetate) has to be converted to slowly degradable COD like microbial storage polymers (e.g. PHA). Phosphate or glycogen accumulating bacteria perform this conversion step most efficiently. In this paper it is shown that the selection of such bacteria in aerobic granules indeed led to stable granular sludge, even at low oxygen concentrations.

Download Full-text