Microbial biotechnology for wastewater treatment into circular economy

In wastewater treatment plants (WWTPs), biotechnological processes imply the activities of microbial consortia to obtain clean water, by transforming organic and inorganic pollutants into environmental-friendly products considered valuable resources. Thus, microbial biotechnology drives the development of circular economy systems integrating environment preservation into bioenergy production and resource recovery. A crucial aspect to optimize bioenergy production and resource recovery is the study of microbial communities operating in WWTPs to be characterized for their structure (types, relationships, and relative amounts of microorganisms) and functions (metabolic and biochemical capabilities). Genome-based analyses, like metagenomics, metatranscriptomics, and metaproteomics (collectively termed omics technologies), are powerful tools to characterize microbial communities. This chapter describes and discusses technological aspects of omics approaches and examples of their applications in WWTP investigations. Particularly, biotechnological aspects and issues that can affect the transition to a circular economy system, where WWTPs play a key role feeding biorefinery systems, are highlighted and commented.