Ammonium Utilization in Microalgae: A Sustainable Method for Wastewater Treatment

Abstract

In plant cells, ammonium is considered the most convenient nitrogen source for cell metabolism. However, despite ammonium being the preferred N form for microalgae, at higher concentrations, it can be toxic, and can cause growth inhibition. Microalgae’s tolerance to ammonium depends on the species, with various taxa showing different thresholds of tolerability and symptoms of toxicity. In the environment, ammonium at high concentrations represents a dangerous pollutant. It can affect water quality, causing numerous environmental problems, including eutrophication of downstream waters. For this reason, it is important to treat wastewater and remove nutrients before discharging it into rivers, lakes, or seas. A valid and sustainable alternative to conventional treatments could be provided by microalgae, coupling the nutrient removal from wastewater with the production of valuable biomass. This review is focused on ammonium and its importance in algal nutrition, but also on its problematic presence in aquatic systems such as wastewaters. The aim of this work is to provide recent information on the exploitation of microalgae in ammonium removal and the role of ammonium in microalgae metabolism.

Nitrogen Starvation Effect Versus its Excess on the Performance of Arthrospira maxima in Zarrouk’s Medium

“…platensis culture medium, as well [41]. According to the current research, chlorophyll-a content decreased with increasing theurea concentration.…”

“…Moreover, urea contains two nitrogen atoms in a molecule with more than 45% of nitrogen while standard Zarrouk's medium was containing 16% of the nitrogen in sodium nitrate [40]. Abd El-Baky [41] found that nitrogen concentration reduction in S. platensis culture decreases phycocyanin, chlorophyll and protein contents due to breaking down the chloroplasts. The concentration of chlorophyll increased when nitrogen was used in the S.…”

Long-Term Cultivation of a Native Arthrospira platensis (Spirulina) Strain in Pozo Izquierdo (Gran Canaria, Spain): Technical Evidence for a Viable Production of Food-Grade Biomass

“…in Arthrospira cultures [52,64], especially when combined with low CO 2 supply and renewal of aliquots of the culture with fresh medium [52], as performed here at each harvesting time during the F experiment (see Section 2.2). Repeated batch addition of NH 4 + is also a very helpful strategy in the treatment of Chlorella and other phototrophs [19,52], and also of contaminant protozoans, due to the predominance of the toxic NH 3 over NH 4 + at high pH values (>9.26 at 25 • C; [65,66]). In this study, removal of Schmidingerothrix was observed the day after the first treatment with ammonium sulphate (Table A3, Appendix B), indicating the sensitivity of this ciliate with respect to ammonia at the dosed amount.…”

Ammonia Bioremediation from Aquaculture Wastewater Effluents Using Arthrospira platensis NIOF17/003: Impact of Biodiesel Residue and Potential of Ammonia-Loaded Biomass as Rotifer Feed

“…Industrial wastewater, agricultural activities, and municipal effluents increase the ammonia nitrogen discharges into environmental resources [ 7 ]. Ammonium pollution affects the aquatic quality of water bodies, resulting in severe environmental problems such as pH shift, cyanotoxin creation, oxygen reduction, eutrophication of downstream liquids, enhanced eutrophication of rivers and lakes, and exhaustion of dissolved oxygen, being toxic aquatic animals at a level greater than 1.9 mg·L −1 [ 8 , 9 ].…”

“…Recently, microalgae have been discussed as a valuable feedstock for many applications, including biofuel production [ 14 , 15 ]. It was calculated that roughly 40–100 kg of inorganic nitrogen compounds and 11–13 ML/Ha/year of water are required for 1 ton of microalgal growth [ 8 ]. It was also anticipated that roughly 2500 m 3 of wastewater might be processed to produce 1 ton of microalgal biomass [ 16 ].…”