Algae-Based Phosphate Removal: A Sustainable Approach to Wastewater Treatment

Wastewater contamination with phosphates poses significant environmental challenges, primarily due to human and animal excretion, as well as residues from fertilizers and cleaning agents. These phosphates act as fertilizers in water bodies, contributing to the phenomenon of eutrophication—an excessive accumulation of nutrients that triggers harmful plant and algae growth. Consequently, phosphate removal is a critical step in wastewater treatment to maintain ecological balance.

Phosphate Removal Methods

In wastewater treatment plants, the removal of phosphorus is traditionally achieved through a chemical process known as phosphate precipitation. During this process, metal salts are added to bind the dissolved phosphates, which then precipitate as insoluble compounds. These compounds can subsequently be separated from the water. However, many of the precipitating agents used are by-products or waste materials from industrial processes, which may contain heavy metals. These metals can accumulate in sewage sludge, presenting an undesirable side effect.

An alternative to this chemical method is the use of biological processes, such as algae-based phosphate removal. Algae have the ability to absorb phosphates as nutrients and metabolize them for growth. Rather than creating sedimented metal phosphates, this biological approach generates biomass, which can be separated and processed through the sewage sludge. The advantage of this method lies in its potential for producing valuable biomass instead of harmful by-products.

Research on Algae in Wastewater Treatment

At the competence center for sustainable engineering and environmental systems (ZEuUS) at the Technical University of Mittelhessen, Prof. Ulf Theilen and his team are exploring the potential of algae in wastewater treatment, focusing on both nutrient elimination and the further use of the biomass produced. Two doctoral projects, led by Ms. Tatjana Lorenz and Mr. Nils Hasport, are investigating algae’s role in removing nutrients from wastewater and the material and energetic uses of the resulting biomass.

The researchers are particularly interested in reusing the algae biomass as fertilizer or generating biogas. Due to their rapid growth, algae offer a biogas production potential comparable to that of maize, the current primary substrate for biogas production.