Freshwater is a valuable resource that needs to be managed in a sustainable and responsible manner. However, increased anthropogenic activities have resulted in a rise in freshwater use with a similar trend in the volume of wastewater being generated.
The main aim of wastewater treatment is to remove the carbonaceous matter and also in the elimination of phosphorus (P) and nitrogen (N) as high concentrations of these nutrients in wastewater can lead to eutrophication of surface waters.
Currently, wastewater treatment is performed through biological processes, such as the activated sludge process or the biological nutrient removal process which are conventionally termed the secondary treatment phase. These secondary treatment processes are dependent on oxygen to enable the endogenous microorganisms present to breakdown and assimilate the organic and inorganic matter. This stipulation for oxygen comes at a high cost with wastewater treatment consuming approximately 1% to 3% of the total electricity generated in developed countries of which 40% to 60% is expended on supplying air to the aeration basin. The precise amount of energy consumed varies depend on the wastewater source, treatment process employed and effluent quality required. On top of this, the cost to treat wastewater is projected to rise as a result of growing urbanisation and more stringent effluent quality requirements.
Whilst wastewater treatment is necessary in the cycle of freshwater and to protect the environment, the energy to treat wastewater is high and it is imperative that more efficient and reliable processes are developed. Hence, adapting microalgae to treat wastewater could form an inexpensive solution to treating wastewater while also generating a renewable feedstock.