A review of biogas slurry treatment technology based on microalgae cultivation

Combining anaerobic digestion with microalgae cultivation has been increasingly explored as an environmentally-sustainable means of energy recovery and nutrient removal from biogas slurry (BS); however, due to the unique characteristic of BS (i.e., its high chemical oxygen demand (COD); high ammonium, total phosphate (TP), and total nitrogen (TN) content; high turbidity; and heavy metal content), significant challenges to large-scale application existed, including potential negative interactions among BS components and microalgae. This review identifies several physicochemical characteristics of BS that inhibit microalgae growth and, thereby, affect both BS remediation and microalgae biomass production. The potential inhibition of algal growth by heavy metals is also discussed, and progress in the pretreatment of BS for microalgae cultivation is examined. • Microalgae cultivation-based treatment of anaerobic digestates is reviewed. • Turbidity, ammonium nitrogen, native microbes and COD in BS are the key challenges in BS-microalgae treatment system. • Pretreatment of BS currently employed to overcome these challenges are reviewed.