Algae Filter

for production of sustainable fertiliser

Algae is well known for its capacity to absorb nutrients from water and enrich soil. For fertiliser production, the difficulty lies in finding a safe and effective system that provides optimal conditions for growing large quantities of algae in a local water body, efficiently removing it from the water, and testing its suitability for fertiliser.

Such a system--the subject of a joint pilot project conducted by eThekwini Water and Sanitation (EWS) and the city of Bremen--could act as a free source of nutrients for the local population’s flower and vegetable gardens. Making use of solar energy, the algae filter implementation offers the additional advantages of binding carbon and improving water quality by consuming excess nutrients.

During the pilot project’s test phase (March 2013 to mid-2014), team members examined whether:

• the algae can grow and be harvested directly in the uMhlangane River,
• the algae and algae substrate are safe for the environment, and
• the algae and algae substrate can be used as a fertiliser.

The following activities were successfully carried out:

• development of a suitable filtration unit on which the algae can grow
• observation of algae growth
• examination of algae for pollutants
• analysis of various nutrient concentrations

Before the project could be completed, the metal frames used for growing the algae were taken from the river. Theft of metal parts is a serious problem in South Africa, and it hinders the success of several projects that Bremen and Durban are carrying out together.

Without a medium for growing algae, the subsequent steps could not be carried out:

• developing a method for harvesting and drying algae
• training the local population to become proficient in using the algae on a sustainable basis

The algae filter project is currently on hold.