Nutrient removal by alginate‐immobilized Chlorella vulgaris: response to different wastewater matrices

Abstract

BACKGROUND: Immobilized algae are a promising tool to treat wastewater within a short time (<12 h) and simplify biomass harvesting compared with suspended algae. The potential of alginate-entrapped Chlorella vulgaris to bioremediate secondary (with and without nutrient supplementation), primary and two lagoon municipal wastewaters was investigated. The capability of the system to adapt to these wastewaters was analysed by determining biotic and abiotic nutrient removal, and further evaluated by comparison with suspended cells.RESULTS: The algal nitrogen (N) content (4.6-7.8 wt%) was closely related to the wastewater ammonium concentration (R 2 = 0.97). The algal cells did not adapt N uptake as effectively to wastewater nitrate concentration because both abiotic N and phosphorus (P) removal increased. The algal P content (1.2-3.2 wt%) varied in response to the wastewater P and was inversely related to the initial cellular P content. The algae thus adapted nutrient uptake to the wastewater N:P level and ratio when ammonium predominated. Biomass production (35-73 mg L -1 d -1 ) increased with dissolved organic and inorganic carbon with little impact from other wastewater characteristics. Immobilization did not affect N and P uptake per cell compared with suspended algae. CONCLUSION: Decoupling biotic and abiotic removal showed adaptation to the N:P of the wastewater and luxury P uptake had significant impact during treatment of different wastewater matrices, these traits were not affected by immobilization. Immobilization enables increased N and P removal rates compared with suspended algal systems as nutrient uptake per cell is not affected and higher concentrations of algal biomass within the reactor are facilitated.To meet the desired feed nutrient levels 184 mg L −1 NaNO 3 was added to SE1 + NO3, 115 mg L −1 of NH 4 Cl was added to SE1 + NH4, 268 mg L −1 of NaNO 3 to SE2 + NO3, and 156 mg L −1 of NH 4 Cl to SE2 + NH4.Immobilized algae adapt nutrient removal to different wastewaters www.soci.org

A Review on the Reliability and the Readiness Level of Microalgae-Based Nutrient Recovery Technologies for Secondary Treated Effluent in Municipal Wastewater Treatment Plants

“…Another widely researched wastewater treatment reactor configuration is the active immobilized algal bead systems. These reactors resemble the enclosed suspended growth systems with the difference that the algal cells do not float freely into the water medium but are encapsulated into separate beads with specific a biomass concentration inside [39,54]. The beads are preliminarily prepared in a laboratory setting, either through covalent bonding, adsorption, semi-permeable membrane encasing, or polymer enfolding (Figure 5) [39,54,55].…”

“…These reactors resemble the enclosed suspended growth systems with the difference that the algal cells do not float freely into the water medium but are encapsulated into separate beads with specific a biomass concentration inside [39,54]. The beads are preliminarily prepared in a laboratory setting, either through covalent bonding, adsorption, semi-permeable membrane encasing, or polymer enfolding (Figure 5) [39,54,55]. The main reason for the development of such technology is the mitigation of the post-treatment algal harvesting and higher control over the algal monoculture contamination [39,54].…”

“…The beads are preliminarily prepared in a laboratory setting, either through covalent bonding, adsorption, semi-permeable membrane encasing, or polymer enfolding (Figure 5) [39,54,55]. The main reason for the development of such technology is the mitigation of the post-treatment algal harvesting and higher control over the algal monoculture contamination [39,54]. Also, these systems allow for the use of higher algae concentrations that induce processes with a higher intensity [39,54].…”

Analysis of the Status and Improvement of Microalgal Phosphorus Removal from Municipal Wastewater

“…In addition, beads produced by immobilized microalgae can also shield the culture from harmful contaminants in wastewater [109]. Kube [110] demonstrated that different concentrations of nitrogen and phosphorus can influence the absorption of phosphorus by Chlorella and that the immobilization of microalgae does not hinder the rate or ratio of nitrogen and phosphorous absorption. In addition, cell immobilization and co-cultivation of Bacillus vulgaris and P. brasiliensis can boost the removal rates of ammonia and phosphorus [111].…”

Phosphorous remediation using alginate/glomalin biobeads: Examining structural cohesivity, nutrient retention, and reapplication viability

“…Furthermore, C. vulgaris has been successfully used for bioremediation of different wastewater sources due to its robustness, mixotrophic culturing conditions, high growth rate under harsh conditions, and tolerance to high levels of heavy metals (Ge et al, 2013). However, work by Kube et al (2020) suggests that certain environmental conditions may play an inhibitory role in nutrient accumulation. Further, it is possible the immobilization medium could be destabilized in some aquatic conditions (Mohseni et al, 2021).…”