Stirred tank used for process intensification of gas-liquid bioreactors. Photo by: Thorkild Christensen

Algorithm to decrease emissions from wastewater treatment

Wednesday 31 May 17
by Frederik Appel Olsen


Gürkan Sin
DTU Chemical Engineering
+45 45 25 29 80

Facts about LaGas

LaGas is led by the Department of Environmental Engineering at DTU. The Management Board includes members from DTU Environmental Engineering, DTU Chemical and Biochemical Engineering, University of Southern Denmark, Krüger A/S, Veolia Water, Unisense A/S and Copenhagen Wastewater Innovation. It is funded by The Danish Council for Strategic Research (Det Strategiske Forskningsråd).

For more information on LaGas, go to the project site.

During wastewater treatment, the greenhouse gas N2O, also known as laughing gas, is emitted. Sustainability demands that the emission is minimized. The LaGas project at PROSYS is on the case, aiming at controlling N2O production and emission during wastewater treatment operations with a new patent and algorithm.

Laughing gas may sound like a laughing matter but there is nothing funny about a greenhouse gas 300 times stronger than CO2, flowing directly from the processes of wastewater treatment to the atmosphere. But this is, nevertheless, the case of laughing gas or N2O.

The LaGas project is a product of the PROSYS research centre at DTU Chemical Engineering and is led by associate professor Gürkan Sin. The goal is to investigate the production of N2O in wastewater treatment operations in order to find out how best to control emissions.

The project ended this year successfully by patenting a novel control concept. And now, thanks to a new funding that has come in, Gürkan Sin will continue the work on this environmental challenge.

“We were very happy and excited to have the funding from Vandsektorens Udviklings- og Demonstrationsprogram (VUDP) – the Danish water sector’s own funding system - to demonstrate the feasibility of our idea. Our partners in the project are BIOFOS –the biggest Danish water utility company - which provide us a platform to test our novel concept, as well as and Unisense – a specialized sensor company supplying us an N2O sensor,” Gürkan Sin says.

A complicated issue
The issue of N2O emission from wastewater treatment is a hot topic in the international science community. Much work has been done but few decisive results have emerged.

The main lesson learnt from the LaGas project is that the problem of N2O emission is closely related to each treatment plant: How it is designed and how it is operated. Not even this much was clear before the start of the project. In some plants emission is observed, in some plants it is not. Therefore, it is important to understand each plant before you propose a solution because the emission of N2O is depending on the design and control of the individual plant.

The job of engineers, the project concludes, is to specify how to control the operations - e.g. control of aeration system, among others - in the specific treatment plan in order to minimize emissions.

Looking ahead
In Gürkan Sin’s coming research project, a postdoc with a background in process automation and control will be implementing the patented control algorithm in the control system at the Avedøre wastewater treatment plant – one of the plants operated by BIOFOS.

The performance of the treatment plant will be monitored using standard measurements of effluent quality parameters but also N2O emissions to atmosphere by the help of liquid N2O sensor provided by UNISENSE. The hope is to learn from these testing about how the control technology performs in real life with highly varying influent wastewater composition and flows. This will provide directions on how to further revise the principles of the control technology so that it is possible to achieve a significant reduction on the baseline N2O emissions.

Read more about the LaGas project

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