Abstract
The stability of calcium alginate beads for microalgae immobilization in wastewater treatment has been a concern due to the potential exchange of Ca2+ ions from the bead surface with the environment. To overcome this constraint, adding biopolymers might improve the properties of alginate gel. The purpose of the study is to immobilize Chlorella vulgaris in blends of sodium alginate with carboxymethylcellulose (CMC) or pectin in different concentrations (1%, 1.5%, and 2%) to evaluate the microalgae growth and nutrient removal from culture media. The microalgae growth was assessed by cell counting and chlorophyll content using a fluorescent excitation–emission matrix. Nutrient removal was conducted by measuring the phosphate and nitrate concentration using ion chromatography. The characterization of beads, such as size, shrinkage degree, swelling ratio, water content, and dry weight, was also investigated. Compared to alginate-only beads, the results present better performance for cell growth and, similarly, for removing nutrients in the presence of pectin and CMC blends. Microalgae in alginate with 1.0% of pectin grew 26% more than in alginate-only beads on day 8. The blends with CMC showed faster removal of nutrients compared to pectin blends and alginate-only in only 3 days. For phosphate, the highest removal was by immobilized microalgae of 95% for 2.0% of CMC and 86% for 2.0% of pectin. For nitrate, the immobilized microalgae removed 100% in 1.0% and 1.5% of CMC and 98% in 1.0% of pectin.
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