Assessment of algae-based wastewater treatment in hot climate region: Treatment performance and kinetics

Abstract

This study evaluated the use of microalgae for wastewater treatment in hot climate regions. The growth rates of C. vulgaris (C.v.) and N. oleoabundans (N.o.) at 36 °C were studied in primary effluent (PE), secondary effluent (SE) and centrate (CEN) and their performance in removing soluble chemical oxygen demand (CODs), inorganic nitrogen and total dissolved phosphorus were determined. A comprehensive kinetics model was developed to predict algae growth and treatment efficiencies under the studied conditions. Significant differences between the growth patterns and rates of C.v. and N.o. were observed in different wastewater samples. C.v. showed the highest growth rate in CEN followed by PE and SE. N.o. showed the highest growth rate in PE followed by SE and CEN. The percentage CODs removals (%CODs) for C.v. were 51%, 55% and 80%, and for N.o. were 63%, 47% and 72% in PE, SE, and CEN, respectively. Ammonia removal efficiencies (70%–84%) were very similar for C.v. and N.o. in different wastewaters. Phosphorus removal by C.v. and N.o. was high in PE (> 84%), moderate in CEN (>22%) and limited in SE (<15%). Growth rates of C.v. and N.o and percent removals of CODs, ammonia, nitrate and total dissolved phosphorus at 36 °C were compared to those at 20 °C.

The kinetics of algal strains, validated using experimental data, accurately reproduced the growth profile and evolution of organic matter and nutrients, permitting process optimization and scale-up. The results of the study showed that microalgae can be successfully cultivated in a wide range of wastewaters at 36 °C and can achieve natural treatment of wastewaters in hot climate regions by removing organic carbon, nitrogen, and phosphorus.