Soil degradation, overuse of chemical fertilizer, and biodiversity loss are serious problems challenging the sustainable development of modern agriculture. In recent years, owing to the advantages of algae biotechnology in nutrients recovery and soil improvement, the integration of algae‐based wastewater remediation and algal bio‐fertilizer production is emerging into the limelight. In this work, we emphasize on the progresses achieved in the fields of biomass production by algae cultivation in wastewater and application of algal bio‐fertilizers. Particularly, three types of algal bio‐fertilizers, including slow‐release bio‐fertilizer, nitrogen‐fixing cyanobacteria, and liquid bio‐fertilizer, widely evaluated and utilized in agriculture are introduced. To prevent the overly optimistic prediction of algal bio‐fertilizer in a real‐world application, we point out the challenges and technical defects, such as presence of new pollution factors in wastewater, high cost of algal biomass, contamination of algal biomass in wastewater, low productivity of algae and valuable components, high water consumption, and potential threats of cyanobacteria to the environment, that prevent the concept of integrating algae‐based wastewater remediation and algal bio‐fertilizer production from becoming a reality. Based on our knowledge and experience, potential solutions to the aforementioned problems are discussed in depth. It is expected that the emerging technologies of algae‐based wastewater remediation for bio‐fertilizer production will bring human beings into a new era of environmentally‐friendly, high‐yield, and resource‐recycling agriculture. © 2020 Society of Chemical Industry (SCI)

BACKGROUND: Microalgae biotechnology is considered as a promising way to recover nutrients from centrate wastewater for value-added biomass production, but it is rarely adopted in a real-world application. Current study confirmed that carbon deficiency and suspended solids are two problems jeopardizing the microalgae-based wastewater remediation. In this regard, glycerol was added into centrate wastewater as exogenous carbon source and algal-bacterial cooperation for nutrients recovery assessment. RESULTS:The results showed that glycerol addition increased the biomass yield of algae from 1.54 to 2.58 g L −1 in 5-day culture and, at the same time, improved the removal efficiency of nitrogen and phosphorus, which were further assessed by pilot-scale experiments. Bacterial community analysis indicated that algal-bacterial cooperation involves carbon dioxide and oxygen exchange, phosphorus absorption, and solid organics degradation, forming a complementary nexus beneficial for wastewater treatment.CONCLUSION: Glycerol is proven to be a good carbon source for microalgae growth in the centrate wastewater. Additionally, the cooperation between microalgae and bacteria plays a key role in the nutrients removal during centrate wastewater. It is expected the technology and knowledge provided by current work can further promote the industrialization of microalgaebased wastewater remediation. Figure 6. Scheme for microalgae-based centrate wastewater treatment and mechanism of nutrients recovery. www.soci.org M Xu et al.wileyonlinelibrary.com/jctb

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