A half-century of research on microalgae-bacteria for wastewater treatment

The use of microalgae-bacteria consortia (MBC) for wastewater treatment have received increasing attention because of its high capacity for nutrients and organic matter removal, using sunlight as an energy source, through self-sufficient oxygen production provided by photosynthesis. This review addresses the research hotspots and main challenges of this emerging technology, using bibliometric analysis. The evolution of MBC-related literature from 1970 to 2021 was analyzed, identifying of the main research topics explored, based on the frequency of the keywords. This document develops the following topics identified as research hotspots: 1) The factors that influence the complex interactions between microalgae and bacteria (e.g., pH, incident light, dissolved oxygen), and the removal mechanisms of nutrients and organic matter, which are still relevant issues still requiring significant research efforts. 2) The new enhanced pathways of total nitrogen and phosphorus removal, such as short cut nitrogen removal, algammox, and phosphorus luxury uptake, which have been explored during the last decade. 3) The application of mathematical models to represent the behavior of MBC, as a tool for prediction and optimization of MBC systems. And 4) The biomass retention technologies, such as biofilms, membrane bioreactors, and granular sludge; that allows the uncoupling of HRT from SRT, a condition required for high-rate wastewater treatment.