Potential of Chlorella vulgaris and Nannochloropsis salina for nutrient and organic matter removal from municipal wastewater reverse osmosis concentrate

Abstract

Municipal wastewater reverse osmosis concentrate (ROC) poses health and environmental risks on its disposal as it contains nutrients and harmful organic compounds at elevated concentrations. This study compared a freshwater microalga Chlorella vulgaris and a marine microalga Nannochloropsis salina in suspended and alginate-immobilised cultures for batch and semicontinuous treatment of the ROC. The immobilised algae gave comparable nutrient removal rates to the suspended cells, demonstrating immobilisation had no apparent negative impact on the photosynthetic activity of microalgae. Semi-continuous algal treatment illustrated that the microalgae could remove significant amounts of nutrients (> 50% and > 80% for TN and TP, respectively), predominantly through algal uptake (> 90%), within a short period (48 h) and generate 335-360 mg DCW L-1 d-1 of algal biomass. The treatment also removed a significant amount of organic matter (12.7-13.3 mg DOC L-1 d-1), primarily (> 65%) through the biotic pathway.

Use of microalgae for treating municipal wastewater reverse osmosis concentrate and resource recovery

“…Single-cell green microalgae such as Chlorella and Scenedesmus can grow well in wastewater, and are typically the dominant microalgal species in high rate algal ponds (Wollmann et al, 2019). Few species within these genera have been reported as effective for ROC treatment , and in our recent study, Chlorella vulgaris and the marine alga Nannochloropsis salina showed comparatively efficient nutrient removal from a municipal wastewater ROC (Mohseni et al, 2020). However, no systematic studies for identifying the species suitable for achieving the management objectives from a larger number of possible microalgae have been documented.…”

“…Increasing alkalinity to 400 mg/L resulted in algal growth improvement and thus better DOC removal; however, with further increase in alkalinity level (i.e., 600 mg/L), DOC consumption subsequently decreased (Figure 4.8b). The DOC removal rate could be predicted by the empirical model developed (Equation 4.8) with some moderate deviations on testing it against experimental data reported in Mohseni et al (2020) for DOC removal rates of C. vulgaris and N. salina in ROC treatment (MAD of <24%, R 2 =0.86).…”

“…processes contain elevated concentrations of the nutrients and organic pollutants derived from the secondary effluent, which can cause adverse effects on human beings and ecosystems on direct discharge to the environment . Among the many treatment methods for the reverse osmosis concentrate (ROC), microalgae-based treatment technology is emerging as a promising solution for nutrient (N and P) and organic contaminant removal (Mohseni et al, 2020), and resource recovery in the form of algal biomass, which can be used for the production of valuable products such as biofuel .…”

Cultivation and Biorefinery of Microalgae (Chlorella sp.) for Producing Biofuels and Other Byproducts: A Review

“…The composition of municipal wastewater varies greatly because of the substances from various families, businesses, and institutions. For example, the COD and TN in a municipal sludge digestate were 2175 mg L −1 and 840 mg L −1 , and 164 mg L −1 and 43.2 mg L −1 [84], in municipalities with reserve osmosis concentrate [85], respectively. Generally, the COD, TN, and TP utilization efficiencies of municipal wastewater in microalgal Chlorella cultivation were approximately 85-100%, 80-100%, and 90-100%, respectively (Table 3).…”

Bioprospecting of native algal strains with unique lipids, proteins, and carbohydrates signatures: A time dependent study

“…oculata, C. vulgaris, Nannochloropsis salina, Rhodomonas salina and so forth. [3][4][5] and wastewater as well that is, Chlorella sorokiniana, Micractiniumpusillum, Chlorella variabilis and so forth. 6 Surrounding environment (pH, temperature, presence of different salts) of microalgae exert significant effect on its biological pathways that lead to the synthesis of the different metabolites.…”