Project Description

Wastewater treatment

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.

wastewatertreatmentThe 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.

LaurenceLaurence Evans, a PhD student in the Gutierrez Lab, is working to develop a treatment system for primary settled wastewater (PSW) using Chlorella vulgaris in a process with a low energy demand. Current work has examined the treatment efficiency of environmental samples by the microalgae cultured statically with and without organic carbon enrichment. This research has led to the successful running of a semi-continuous treatment of PSW enriched with industrial waste replacing the need for high-grade organic carbon. Results to-date have demonstrated that microalgal culturing processes to treat PSW in bioreactors without aeration offer a promising approach to develop for low cost municipal wastewater treatment options. This work is funded by a Heriot-Watt Water Academy PhD Studentship to Laurence and is in collaboration with the University of Edinburgh and the Schools EGIS and EPS at Heriot-Watt University.