Engineering

Turning wastewater into a resource

Turning wastewater into a resource

Turning wastewater into a resource

Researchers at the Department of Chemistry and Bio Science at Aalborg University have developed a new method for filtering wastewater that is far more efficient than before. This will mean less heavy metals and medicine residue spills in the nature and increased recycling of phosphorus from farm fertilizers.

Warm membranes

Associate Professor Cejna Anna Quist-Jensen and her colleagues are currently working on the development of a new type of membrane to purify wastewater and liquid manure. The membrane works as a kind of coffee filter that allows clean water to pass through but catches and aggregates toxic waste materials and keeps them from spilling into the nature or trickle down into the groundwater. Today, membrane technology is used for wastewater treatment and reverse osmosis for desalinating sea water. Cejna Anna Quist-Jensen’s membrane system deviates by heating up the wastewater as it passes through the filter.

- We heat up the wastewater to about 40-50 degrees. This can be done with solar heating or industrial surplus heating. When the wastewater becomes warm, it can be filtered extremely efficiently in our membrane. The new process is so efficient that the waste materials are held back and the valuable components within it crystallise and become dry matter - instead of the sludge as it usually ends up as today, she says.

Today the phosphorous sludge is used as a fertilizer and spread over the fields. The drawback to this process is, that the sludge – because it is not properly purified – may also contain toxic metals and medicine residue that is unwanted back in the nature.

Wastewater technology versus food crisis

Since the method of adding heat to the cleansing membrane makes it possible to crystallise phosphorous, it presents the opportunity of utilizing and recycling the phosphorous from farm fertilizers much more efficiently than today. And that holds a series of benefits.

Partly because the phosphorous can be kept out of the aquatic environment, but even more importantly because the world’s supply of phosphorous is running critically low. The phosphorous that is used for farm fertilizers is mined in Morocco, Russia, China, and the USA, but within the next 50 – 100 years the mines are going to run dry. This means that we are potentially facing a looming food crisis. Phosphorous is vitally essential to plants and animals, but at the same time toxic to nature and the aquatic environment.

This challenge may be solved using the warm membrane technology.

- When we can utilize wastewater more efficiently and crystallize pure phosphorous with our membrane, we will eventually not have to dig it out of mines in the ground. When we can extract and recycle the phosphorous that would otherwise be polluting the soil we have a strong card to play against future food crises, says Cejna Anna Quist-Jensen.