ICU – improved carbon utilization in a smaller footprint

In the research project ICU, industrial PhD student Elin Ossiansson is testing a new process combination for more efficient wastewater treatment, aiming to generate an equal amount of biogas from the sludge but with reduced energy consumption. After two years of pilot testing at the Källby wastewater treatment plant, the results are promising.

In wastewater treatment, an easily accessible carbon source is needed to provide energy to the bacteria responsible for removing phosphorus and nitrogen from the water. The ICU research project, which stands for Ideal Carbon Utilisation, examines the possibility of utilizing carbon in wastewater more efficiently to reduce energy and surface area requirements in the treatment process.

Elin is an industrial PhD student at VA SYD, affiliated with Chalmers University of Technology and Sweden Water Research. Within the REWAISE project, Elin’s research contributes to the work conducted on the value of water – simply put, utilizing the resources present in wastewater, for example, more effectively.

In her project, Elin has operated a pilot plant at the Källby wastewater treatment plant in Lund for two years to gain insights into how a specific pretreatment can enhance wastewater treatment efficiency while maintaining the same amount of biogas production from the sludge. Additionally, the aim is to achieve a compact design, which is beneficial given the limited space available in many existing wastewater treatment plants due to encroaching urban development.

Results: Increased carbon source for improved and energy-efficient treatment

The pilot plant has been operated with two parallel pilot reactors for hydrolysis-fermentation. The reactors have not been heated but operated at the ambient temperature to save energy. Elin’s research has shown that it is possible to generate the same amount of biogas as before, while achieving improved emission values and reduced volume in the biological treatment.

– The pretreatment provides us with the opportunity to obtain nearly twice as much VFA (volatile fatty acids) compared to without pretreatment. This potentially eliminates the need for adding any external carbon source to the biological treatment, resulting in better treatment that is also more energy-efficient and compact,” says Elin Ossiansson.

What are the results after two years of pilot testing?

– The results are promising! The process has been reliable, stable, and robust. Extensive knowledge has been gained due to the extended duration of the pilot plant operation, says Elin. Effective particle separation has been achieved, as particles larger than 10 micrometers have been successfully removed, preventing their entry into the subsequent treatment steps.

What happens next?

A report on the project will be released by SVU (Svenskt Vatten Utveckling) soon, along with scientific articles. Elin will continue her work on the next step, which involves incorporating filters alongside biological treatment. On Monday, June 12, Elin will present her midterm seminar; more information can be found here.

What does the process entail?

First, the water is filtered using a rotating belt filter, and then the sludge is fermented to produce the carbon source. The incoming wastewater is flocculated with polymer and filtered, resulting in filtered wastewater and filter sludge. The filter sludge is then used in the hydrolysis and fermentation reactors. The output of hydrolysis and fermentation is a carbon source in the form of VFA, which is utilized in the biological treatment stage. The particles in the sludge can be separated and used for biogas production. This untested process combination has the potential to form the foundation for more efficient wastewater treatment.

More information about Elin’s research can be found here.