Study maps the global activated sludge microbiome

Despite activated sludge being the predominant biological wastewater treatment technology in the world, the global activated sludge microbiome has remained unmapped, until now…

Developed over a century ago, activated sludge is a sewage and industrial wastewater treatment process involving aeration and a floc composed of biological microorganisms such as bacteria and protozoa. When mixed with wastewater, the microorganisms consume the biodegradable organic material and clump to form a solid mass that can be separated from the treated water.

Developing a comprehensive understanding of the biodiversity of the activated sludge microbiome in relationship to treatment performance is deemed critical to advancing and optimising wastewater treatment technology and re-use systems. Enhancing these systems via microbiome engineering will be critical to global health and sustaining a world population predicted to reach 10 billion by 2050.

In response to the knowledge gap relating to activated sludge components at different treatment plants, an interdisciplinary global study was led by researchers at the University of Oklahoma (OU). The research involved the collection and analysis of hundreds of samples from municipal wastewater treatment plants across the world, resulting in an expansion of our understanding of global activated sludge microbiomes.

As part of the initiative, in May 2014 the Global Water Microbiome Consortium (GWMC) was established to promote international collaboration and communication on global water and wastewater microbiome studies. Consisting of researchers from 23 countries, around 70 research groups from different universities and organisations have taken part in the GWMC. The aim of GWMC initiatives is to provide a system-level mechanistic understanding of the diversity, distribution, succession and stability of global water and wastewater microbiomes using high throughput metagenomic technologies.

Professor Jizhong Zhou, Director of the Institute for Environmental Genomics at OU, explained that, "Different from several other global initiatives using a bottom-up approach to solicit microbial samples, the consortium used [a] top-down sampling strategy to target the microbiomes of activated sludge processes in municipal wastewater treatment plants that represent a vital element of the infrastructure for modern urban societies. The campaign involved 111 investigators who sampled 269 wastewater treatment plants in 86 cities in 23 countries on six continents," he said.

As a result of the global initiative, around 1200 activated sludge samples have been collected and analysed, with results published in Nature Microbiology.

What makes this study novel?

The global study of activated sludge microbiomes:

• is the first comprehensive, coordinated effort to examine the global diversity and biogeography of the activated sludge microbiome;
• documents a highly diverse activated microbiome, containing up to one billion microbial phylotypes comprising novel species;
• identifies the core global taxa of activated sludge microbial communities that are linked to activated sludge performance;
• reveals that the activated sludge microbiome is distinct from microbiomes in other habitats;
• provides an understanding of the mechanisms driving the composition and functions of activated sludge communities.
   

Bruce Rittmann, Director of the Biodesign Institutes' Swette Center for Environmental Biotechnology at Arizona State University, said, "This unprecedented global sampling effort [has] yielded new insight into the microbiology of activated sludge.

"Despite giant geographic differences, the microbial communities of activated sludge have a core of about 28 bacterial strains, which reflects the powerful and unique ecological selection of the activated sludge process."

Lisa Alvarez-Cohen, Fred and Claire Sauer Professor of Environmental Engineering at the University of California, Berkeley, also commented on the research project: "This expansive study is the first time that a systematic study of the hugely beneficial microbial communities involved in the biological treatment of daily wastewaters from communities around the world have been studied to understand their fundamental structure and function has been undertaken. It represents an important development in understanding and maintaining these crucial microbial communities," she said.

Image caption: An OU study expands the understanding of activated sludge microbiomes for next-generation wastewater treatment and re-use systems enhanced by microbiome engineering. Image credit: University of Oklahoma.