Municipal Wastewater Effects on the Performance of Nutrient Removal, and Lipid, Carbohydrate, and Protein Productivity of Blue-Green Algae Chroococcus turgidus

Abstract

The use of microalgae in wastewater treatment (WWT) is seen as a promising and sustainable alternative to conventional WWTs, and the obtained biomass is gaining importance as a bio-product. The present study aimed to investigate the effectiveness of using municipal wastewater (MWW) as a nutritional supplement for the cultivation of the cyanobacteria Chroococcus turgidus (Kützing) Nägeli 1849 and the pollutant removal potential of the microalgae. The WW received from the different treatment stages (primary, secondary, and final effluent) was applied to the microalgae culture, and algal growth was compared with regard to growth rate, nutrient removal efficiency, and final algal lipid (%) and protein (%) content. In 7-day batch experiments, except for BOD5 analysis, COD, PO4-P, and N forms analyses were carried out daily in parallel with in vivo Chl-a and Chl-b, DO, pH, temperature, and conductivity measurements. The growth rates and Chl-a quotas of the microalgae grown in trials were different, and the highest growth rate was with a 1.03 ± 0.06 d−1 in the primary effluent (PE). The highest Chl-a and Chl-b quotas among WW trials of microalgae were obtained from the PE trial as 252.4 ± 2 µg L−1 and 112 ± 18 µgL−1, respectively. NH4-N, NO3-N, NO2-N, PO4-P, BOD5, and COD treatment efficiencies were in the ranges of (74.6–83%), (16–71.2%), (22.2–63.6%), (89–95.3%), (50–76.2%), and (70.3–78.6%), respectively. The microalgae were observed to accumulate the highest lipid (28.05 ± 2.26%DW) content in secondary effluent (SE), the highest carbohydrate (43.93 ± 1.02%DW) content in the effluent (E), and the highest protein content (35.25 ± 1.22%DW) in the PE. The results of this study suggested that C. turgidus is a new candidate for bioremediate pollution load of MWW, and its biomass has the potential to offer options in bio-product applications.