Phosphorus from Wastewater

The demand for phosphate-based fertilizers is growing steadily. At the same time, the purity of phosphorus reserves is declining and hence production costs are increasing. There is no substitute for phosphorus. A suitable and cost-effective process for recovering the nutrient had not been been developed so far.

Iosif Mariakakis and colleagues, Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB), Stuttgart, Germany, developed the electrochemical process ePhos^®. It recovers phosphorus from wastewater in a form that is ready for use in agriculture.

An electrolysis cell extracts nitrogen and phosphorus using a magnesium electrode. This results in either struvite (magnesium ammonium phosphate) or potassium struvite. Struvite is free of biomass and can be used directly in agriculture as a high-quality fertilizer that releases nutrients slowly. Unlike traditional methods, there’s no need to add salt or lye. Results from long-term trials at a pilot treatment plant showed that the process was able to recover about 85 % of the phosphorous on average.

A licensing agreement was recently signed with water treatment system provider Ovivo, Montreal, QC, Canada. It markets the technology now in the United States, Canada, and Mexico. Due to the stringent limits associated with water treatment, there is considerable demand for efficient ways of extracting phosphorous. Moreover, many of the water treatment plant providers in the USA are also looking to sell the struvite, which they consider as an attractive source of income. By the end of September, the first industrial-scale demo plant will be up and running in the USA. The Fraunhofer Institute IGB is searching further licensees to introduce the technology on the European market, as well.

The researchers plan to expand ePhos^® by adding processing modules that allow water treatment plants to recover ammonium, too.

ePhos^® – Electrochemical Recovery of Phosphorus,
Iosif Mariakakis, Uwe Claußnitzer, Jennifer Bilbao, Siegfried Egner,
Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB Annual Report 2015/16, Stuttgart, 2016.

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