Abstract
Microalgae have received much attention in the last few years. Their use is being extended to different fields of application and technologies, such as food, animal feed, and production of valuable polymers. Additionally, there is interest in using microalgae for removal of nutrients from wastewater. Wastewater treatment with microalgae allows for a reduction in the main chemicals responsible for eutrophication (nitrogen and phosphate), the reduction of organic substrates (by decreasing parameters such as BOD and COD) and the removal of other substances such as heavy metals and pharmaceuticals. By selecting and reviewing 202 articles published in Scopus between 1992 and 2020, some aspects such as the feasibility of microalgae cultivation on wastewater and potential bioremediation have been investigated and evaluated. In this review, particular emphasis was placed on the different types of wastewaters on which the growth of microalgae is possible, the achievable bioremediation and the factors that make large-scale microalgae treatment feasible. The results indicated that the microalgae are able to grow on wastewater and carry out effective bioremediation. Furthermore, single-step treatment with mixotrophic microalgae could represent a valid alternative to conventional processes. The main bottlenecks are the large-scale feasibility and costs associated with biomass harvesting.
Highlights
A growth in the global population has coincided with agricultural intensification, industrial development, and urbanization, leading to a sharp increase in waste production and environmental pollution [1,2]
The literature data relating to biomass production, expressed in g L−1, volatile suspended solids (VSS) g L−1 or suspended solids (SS) g L−1 ; maximum specific growth rate, expressed in d−1 or h−1 and productivity, expressed in g L−1 d−1, g m−2 d−1, g VSS m−2 d−1, g VSS L−1 d−1, total suspended solids (TSS) g m−2 d−1 and g SS L−1 d−1 were identified and complied in Table S1, Table S2; Table S3; Table S4 and Table S5
Microalgae can be grown on raw urban wastewater, treated urban wastewater and other wastewater such as digestate and centrate, deriving from the anaerobic digestion of activated sludge
Summary
A growth in the global population has coincided with agricultural intensification, industrial development, and urbanization, leading to a sharp increase in waste production and environmental pollution [1,2]. Among the various problems faced by modern society is the need for effective and sustainable management of urban wastewater. Untreated wastewaters can lead to the eutrophication of aquatic environments and represent a serious threat to water bodies. It is necessary to apply appropriate treatment plans for the abatement and removal of substances such as ammonia (NH4 + ), nitrate (NO3 − ) and phosphate (PO4 3 − ) [1,3]. It is necessary to recycle nutrients and recover water: these, if recycled, can be considered a resource rather than waste [5]
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