It is known that MPs, which have become one of the important environmental problems of today in the sludge of WWTPs. It is seen that almost half a million MP particles are detected on 1 kg of dry sludge. Considering that nearly million tons of sewage sludge is produced all over the world per day, it is seen how big the problem is. Unfortunately, it is clear that current sludge treatment processes have not been successful in MP removal and effective treatment methods are needed. It is seen from a limited number of studies that MPs and depending on their types and doses can have negative effects on the amount of biogas in the anaerobic digestion process.

If we look at plastics, although they are materials that are resistant to degradation, there can be significant changes in their basic properties as a result of exposure to various stressors. After this exposure, they may become susceptible to further decomposition. Especially acid, alkaline conditions, heat treatments and exposure to UV radiation are known as stress conditions for many plastics.

In order to increase the amount of biogas produced in the anaerobic digestion process and to reduce the amount of sludge, disintegration processes based on solubilizing the sludge structure accelerate the digestion process and increase the efficiency of the process. The widely used methods of alkali, enzymes, and heat treatment in disintegration appear to be interestingly (and indeed expected) analogous to conditions that create stress for plastics.

In our research, we try to find answers to the questions of how MPs (PET, PP and PC, which have not been studied before) affect biogas production in anaerobic digesters, how this effect occurs when disintegration is applied, and how MPs are affected by different disintegration methods and subsequent anaerobic digestion process.

Our project has 3 main objectives.

1. The aim of the research is to determine how PET, PC and PP MPs, which are frequently encountered in sewage sludge and have not been studied in this context, are affected by different disintegration methods of sewage sludge,
2. how the presence of disintegrated and untreated MPs affects anaerobic digestion processes, what effect they have on biogas production and reactor performance; and
3. how the disintegration process and the subsequent digestion process affect the polymer properties of these 3 plastics.

In line with these goals, we have completed the second year of our project, which we started on October 1, 2021.

Principal investigator

Faika Dilek Sanin