Effects of Nutrient Content and Nitrogen to Phosphorous Ratio on the Growth, Nutrient Removal and Desalination Properties of the Green Alga Coelastrum morus on a Laboratory Scale

Abstract

In wastewater, nutrient concentrations and salinity vary substantially, however, the optimal N:P ratio for the treatment using microalgae is not well described. In this study, the effects of higher and lower nitrate and phosphate contents and N:P ratios on growth, nutrient removal ability and halotolerance of the common green alga Coelastrum morus were investigated in model solutions. The results suggest that high nitrate content (above 100 mg L−1) with a similarly high phosphate concentration (resulting low N:P ratio) is not favorable for growth. The studied isolate can be considered as a halotolerant species, showing remarkable growth up to 1000 mg L−1 NaCl and it seems that despite the negative effects on growth, higher nutrient content contributes to higher halotolerance. A significant amount of nitrate removal was observed in media with different nutrient contents and N:P ratios with different salt concentrations. High N:P ratios favor phosphate removal, which is more inhibited by increasing NaCl concentration than nitrate uptake. Overall, with a relatively higher nutrient content and a favorable (5 or higher) N:P ratio, a common green algal species such as C. morus could be a promising candidate next to species from the Chlorellaceae and Scenedesmaceae families.

The Effects of Photobioreactor Type on Biomass and Lipid Production of the Green Microalga Monoraphidium pusillum in Laboratory Scale

“…Literature data show in the case of several green algae species that high N:P ratios are favorable for phosphate uptake [59][60][61][62][63][64]. Similarly, the used M. pusillum strain took up more phosphate in control cultures (with a higher N:P ratio) than in nitrate-depleted cultures in the case of the tank reactor.…”

A Comparative Study of the Growth and Nutrient Removal Effects of Five Green Microalgae in Simulated Domestic Sewage

“…The microalgae biomass of P. kessleri grows rapidly, reaching 376.667mg L −1 in three days [51]. The biomass concentration of the remaining three microalgae exceeded 200 mg L −1 on the third day [52][53][54]. However, the biomass concentrations of the four microalgae T. obliquus, P. kessleri, Hydrodictyon sp., and S. quadricauda were lower compared with previous studies.…”

Nutrient Removal by Algae-Based Wastewater Treatment

“…This is partly due to the nitrogen to ] phosphorous (N/P) ratio in wastewaters, which plays a critical role in ensuring an effective and simultaneous uptake of nutrients and biomass growth in algae species [15••]. The suitable ratio of N and P for macroalgae growth is between 10 N:1P and 80 N:1P [25] with optimal ratio of 30 N:1P, while it is 5-30 N:1P for microalgae [26,27]. The optimal N/P ratio is strain-dependent; for example, it is reportedly 7 and 30 for Chlorella sp.…”