Microalgal Growth and Nutrient Removal Efficiency in Non-Sterilised Primary Domestic Wastewater

Abstract

Microalgae biomass can produce high quantities of biochemicals that can be used in various applications such as biodiesel, biogas, and aquaculture feed. The potential of sterilizing wastewater for microalgae-based wastewater treatment on a lab scale is well introduced. However, the operation cost for large-scale microalgae cultivation in wastewater treatment plants is high if using sterilising wastewater as the growth medium. The present study aimed to evaluate the growth of Scenedesmus sp., Chlorococcum aquaticum, Ankistrodesmus augustus, and Haematococcus pluvialis in non-sterilised domestic wastewater and their potential for pollutant removal in wastewater. The microalgae were cultivated in different concentrations of non-sterilised domestic wastewater, collected from a primary wastewater plant of a national sewerage company in Malaysia. Each species’ capacity for growth and the removal of pollutants were assessed. The results showed that the cell density, maximum biomass productivity, and biomass concentration of H. pluvialis, Scenedesmus sp., and C. aquaticum in 100% wastewater were significantly higher than the standard medium. Higher biomass concentration was obtained from H. pluvialis and C. aquaticum in 100% wastewater (815 g/L and 775.83 mg/L); nevertheless, Scenedesmus sp. in 100% wastewater yielded the highest specific growth rate (0.798 d−1) and the maximum biomass productivity (99.33 mg/L/day). Scenedesmus sp. in 100% wastewater also achieved better removal efficiency of total nitrogen (TN), total phosphorus (TP), and ammonia (N-NH4) with more than 90%. All tested microalgae species successfully remove nitrogen, ammonium, and phosphorus and reach the concentration limits set by the Department of the Environment, Malaysia. This study demonstrated that microalgae can grow well in non-sterilised domestic wastewater while simultaneously removing nitrogen and phosphorus effectively.