Toward an Ecologically Optimized N:P Recovery from Wastewater by Microalgae

Abstract

Global stores of important resources such as phosphorus (P) are being rapidly depleted, while the excessive use of nutrients has led to the enrichment of surface waters worldwide. Ideally, nutrients would be recovered from wastewater, which will not only prevent eutrophication but also provide access to alternative nutrient stores. Current state-of-the-art wastewater treatment technologies are effective in removing these nutrients from wastewater, yet they can only recover P and often in an insufficient way. Microalgae, however, can effectively assimilate P and nitrogen (N), as well as other macro- and micronutrients, allowing these nutrients to be recovered into valuable products that can be used to close nutrient cycles (e.g., fertilizer, bioplastics, color dyes, and bulk chemicals). Here, we show that the green alga Chlorella sorokiniana is able to remove all inorganic N and P present in concentrated toilet wastewater (i.e., black water) with N:P ratios ranging between 15 and 26. However, the N and P uptake by the algae is imbalanced relative to the wastewater N:P stoichiometry, resulting in a rapid removal of P but relatively slower removal of N. Here, we discuss how ecological principles such as ecological stoichiometry and resource-ratio theory may help optimize N:P removal and allow for more effective recovery of N and P from black water.

How to combine CO2 abatement and starch production in Chlorella vulgaris

“…However, our results show that C. vulgaris needs more nitrogen input than other microalgal species such as Nannochloropsis, Rhodomonas, Isochrysis or Choricystis to render the maximum biomass productivity [56,57]. Notwithstanding, we consider that this characteristic must be considered when using this microalga in wastewater treatments [58][59][60].…”

Effects of Liquid Digestate Treatment on Sustainable Microalgae Biomass Production

“…Only in variant 1, series II (50% DLD), the final A. platensis biomass concentration was equal to that measured in control (p > 0.05). Other researchers found the maximum biomass production of Chlorella sorokiniana of 12,000 mg TS/L using anaerobically treated black water as a growth medium [48]. Yang et al [49] achieved the maximum biomass concentration of Chlorella pyrenoidosa of 3.01 g/L using anaerobic digested starch and alcohol wastewaters, while Tan et al…”

“…It should be noted that the N/P ratio affects the microalgae biomass productivity, and the required ratio is strictly dependent on the microalgae species [15]. According to Fernandes et al [48], the green alga Chlorella sorokiniana was able to efficiently remove nutrients from wastewaters with N/P ratios ranging between 15 and 26. In turn, Yu et al [10] indicated the optimal N/P ratio for Chlorella varied between 5 and 15.…”

Biodegradation of Doxylamine From Wastewater by a Green Microalga, Scenedesmus obliquus

“…Microalgae-based biotechnologies have shown potential applications for advanced treatment of different wastewaters such as municipal wastewater, swine wastewater, poultry litter anaerobic digestate, industrial wastewater, and aquaculture wastewater (Yu et al, 2015;Zhuang et al, 2020). Additionally, microalgae can utilize the nutrients and carbon sources of wastewaters for their cellular metabolisms with generating biomass for production of bioenergy and high value-added compounds (Perez-Garcia et al, 2011;Fernandes et al, 2017). Microalgal treatment of PCs needs further exploration to achieve potential application under current scenario; in particular, more attention should be paid on the development in the performance for removal of nutrients and PCs from real wastewaters.…”