Phosphorus is an element that is essential in life because of its importance in agriculture and many other industries. But phosphorus is also a finite resource and without a way of recycling phosphorus, there is a danger of running in short supply. This phosphorus crisis may not be as publicised as other resources, but its deficiency will have no less of an impact.
Teams of researchers from Norway are figuring out a way of recycling phosphorus from wastewater more efficiently than just using it for agricultural use.
SINTEF, an independent research organization, has partnered with the Norwegian University of Science and Technology (NTNU) and the Norwegian University of Life Sciences (NMBU) to conduct research on improve recycling phosphorus from wastewater in a research project called Recover.
Herman Helness, a Senior Researcher at SINTEF, said that their role in the Recover project is primarily to “develop wastewater treatment processes that ensure that phosphorus is recovered using as little energy as possible. We’re working on a forward osmosis-based approach that may be suitable for coastal sewage cleaning plants.”
“Phosphorus is a finite resource, not only physically, but also politically,” says Helness. “Most of it is found in the western Sahara occupied by Morocco, and in China. So, in political terms, it is desirable to identify alternative sources,” he says.
Biosolids that come from treated wastewater are a rich source of phosphorus and is generally used as fertilizer, but the soils do not fully utilize the phosphorus that it receives from biosolids and it usually ends up in agricultural runoff. The Recover project aims to develop a method of recycling phosphorus contained wastewater so it can be used to its full potential.
“Future regulations will probably place restrictions on farmers’ ability to use sludge as agricultural fertilizer due to requirements related to the maximum content of phosphorus in the sludge,” says Helness. “This is a sufficient additional incentive for finding methods that enable the recovery of phosphorus from the sludge and to exploit it more effectively than in the past,” he says.
SINTEF believes that the method of forward osmosis offers the optimal exploitation of phosphorus. In this process, the water molecules move from a solution with a higher water concentration to one with a lower water concentration through a semi-permeable membrane.
High concentrations of salt in the seawater will pass easily through the membrane which makes this method ideally suited for coastal sewage cleaning plants. All the phosphorus are kept back on the wastewater side for easy extraction.
“The principle of osmosis means that there is no need to input additional energy to achieve the desired effect,” explains Helness. “The water that passes into the sea is very well cleaned, and we are left with a concentrated flow of sludge on the wastewater side from which we can recover the phosphorus,” he says.
NTNU’s participation in the project is to is to find biological recovery methods of phosphorus. They are cultivating a group of phosphorus-accumulating microorganic bacteria for this process, but the results are still not optimal for their needs.
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