System Turns Sludge Into Biogas

May 14, 2019

TreaTech research has found a way to turn sludge from wastewater treatment plants into mineral salts and biogas

TreaTech developed a new system that has turned sludge from wastewater treatment plants into mineral salts and biogas. According to, the TreaTech research is funded by multiple entities, and a pilot plant is now being built.

Previously, plant operators disposed of this sludge directly as fertilizer. However, it was made illegal in Switzerland more than 10 years ago due to the growing concentration of pollutants found in effluents, according to TreaTech's system also can produce biogas from the effluent with thermal gasification.

The sludge in the system is 95% water and is dehydrated by wastewater plants. According to, the residue is incinerated elsewhere.

"Our system can recover sludge directly from wastewater treatment plants without any drying or other preliminary processing needed," said Frédéric Juillard, TreaTech CEO.

The effluent stream is fed into a high-pressure and high-temperature separator where the fluid enters a critical state. This lowers the solubility of phosphorus and mineral salts in the fluid, according to "Over 90% of phosphorus can be recuperated," Juillard said.

According to, some wastewater treatment plants have systems for recycling sludge into biogas. The technology also saves a lot of time. According to, the reactors can turn sludge into biogas in 20 minutes.

"But biodigesters they currently use can convert only 40 to 50% of the organic matter," said Gaël Peng, co-founder and CTO of TreaTech. “Sludge processing and disposal account for around 40% of a wastewater treatment plant's total operating costs.”

TreaTech also is currently building a pilot plant that can treat 100 kg/h of sludge. The plant should be completed by the end of 2019, and is scheduled to be installed at a wastewater treatment plant in 2022, according to The company wants to adapt the system for use in other applications, like treating industrial wastewater, biomass residue and wastewater from desalination plants.