Extraphore™ from Saur finds a new and valuable use for phosphorus extracted from wastewater
Since the 1950s, phosphorus has been a key ingredient of all the fertilisers used to improve agricultural yields. But the phosphate it is derived from is not a limitless resource, and its availability could easily trigger increasingly serious geopolitical tensions in future years. So what is the solution? The answer to that question is recovering phosphorus, and especially that contained in wastewater.
The R&D engineers at the Saur Group are actively working on processes that recycle phosphorus extracted from wastewater. In the majority of wastewater treatment plants, phosphorus is removed from treatment sludge either using a physicochemical phosphorus removal process in which phosphorus is precipitated by an iron-based or aluminium-based chemical reagent, or using a biological process in which bacteria are used to accumulate the phosphorus. The Extraphore™ process developed and patented by Saur targets a 90% biological phosphorus removal target to minimise the use of chemical reagents, and therefore cost. By instrumenting the biological phosphorus removal process, it is possible to control conditions in ways that encourage bacteria that accumulate the phosphorus, especially in the anaerobic zone on the input side of the biological treatment tank.
This technology has been trialled at two wastewater treatment plants with capacities of 220,000 and 28,000 PE in the Gard and Morbihan regions of France. Although the process has yet to be optimised under real-life conditions on an industrial scale, Saur nevertheless remains confident that worthwhile operational savings can be made. “The programmers and sensors used to control the phosphorus removal process are low-cost, and we already know that there will be significant savings to be made in terms of reagents”, explains research engineer Vincent Jauzein. On the other hand, the phosphorus extraction and recovery phase currently remains at the research stage.
“Extraphore has the potential to be used in all wastewater treatment plants, regardless of size”.
At the wastewater treatment plant in the Gard region, Saur has developed a pilot plant capable of treating around 1 cubic metre of sludge per day.
The Extraphore pilot plant at the Saur wastewater treatment plant in Nîmes”Once the bacteria have done their job of super-accumulating the phosphorus, physicochemical conditions are created in the anaerobic phase that encourage them to release the phosphorus, which can then be precipitated”, continues Vincent Jauzein. The addition of lime causes the formation of hydroxyapatite. The company is currently studying the potential markets and profitability of such a facility. Extraphore has the potential to be used in all wastewater treatment plants, regardless of size; the only precondition being that they have the equipment necessary for biological phosphorus removal.
Plans are already in place to launch the first industrial scale project in the south of France during the first half of 2017.
The recycling of phosphorus to protect the natural resource is a major challenge.
Current reserves are estimated at 16 billion tonnes, and are found mainly in three regions of the world: Morocco and the Western Sahara, China and the USA. Global demand is estimated at 150 million tonnes per year, and more than 90% of the 950,000 tonnes consumed every year in Europe is imported. Given the virtually exponential rate at which demand is growing, all the world’s phosphate mines (phosphate being the ore from which phosphorus is extracted) will be exhausted by the end of this century.
Recovering phosphorus from the wastewater treatment process in wastewater treatment plants could alone meet between 15% and 20% of demand. The Extraphore™ process developed by Saur and now at the experimental stage is therefore of enormous potential importance, since it contributes to making the best-possible use of phosphorous, which is an essential component of phosphate-based fertilisers, without which it will be impossible to feed the world’s population.