Increased emissions when the waste-water plant catches a cold

​In wastewater treatment plants, the work is often done by bacteria, who carry out biological processes used to break down the pollutants and purify the water. Like bacteria, viruses are everywhere around us, and the fact is that bacteria just like other living things can be infected by viruses. Oskar Modin, Professor at the Water Environment Technology Division, Department of Architecture and Civil Engineering, has tested the thesis that a wastewater treatment plant can catch a cold.   

 – A large treatment plant has billions of bacteria that work in a treatment process called activated sludge. 
The bacterial communities are constantly exposed to viruses that infect them, so the question we asked ourselves was whether the process can periodically be more exposed and what happens then, says Oskar Modin.   
Oskar and fellow researchers measured the concentration of virus particles that were released from four different wastewater treatment plants in Sweden and compared it with how much organic carbon was released at the same time.   

 – When we measured virus particles in the water, we found a connection between viruses and organic carbon – when there were more viruses, there was also more organic carbon in the outgoing water.   
Removal of dissolved organic carbon from wastewater is important as it would otherwise lead to increased oxygen consumption where the purified water is discharged, affecting the aquatic environment nearby. The fact that the treatment plant's smallest workers can catch a cold and as a result perform worse, is important to investigate further. Not least to be able to prevent or relieve the symptoms and thereby maximise the effectiveness of the bacteria. But tea with honey, or home remedies with ginger and lemon won’t do when it comes to bacteria.   

 – Viruses are often specialised in a certain species, which means that humans and bacteria cannot be infected by the same virus. One possible way to influence the number of viruses in treatment plants could be to adjust the way the treatment plant is operated. We saw differences between the treatment plants in the study, which we believe may be related to the design or control of the biological treatment processes, says Oskar.   

Researchers do not yet know exactly how the cold manifests itself in the bacteria and to what extent the virus affects the purification processes. Oskar and his colleagues continue to investigate the question in other systems where viruses and bacteria interact, and hope to look at a longer period of time and whether season, temperature and other factors have any significance.   
The paper “A relationship between phages and organic carbon in wastewater treatment plant effluents” was published in Water Research X in August 2022, and written by Oskar Modin, Nafis Fuad, Marie Abadikhah, David l’Ons, Elin Ossiansson, David J. I. Gustavsson, Ellen Edefell, Carolina Suarez, Frank Persson, Britt-Marie Wilén.  The researchers are based at Chalmers and Lund University.