TÜBİTAK 121Y156 - Investigation of the Effects of Microplastics on the Anaerobic Decay Processes of Disintegrated Sewage Sludges and Their Fate in These Processes
Microplastics (MPs) are particles smaller than 5 mm that can be easily transported in environmental systems. Due to the widespread use of plastic in everyday life, MPs end up in wastewater treatment plants (WWTPs) in large quantities. Studies have shown that MPs of WWTPs in wastewater can be removed at a high rate, but they accumulate in sewage sludge, another product of the plant; revealed the MP concentration in the sewage sludge as 510 – 495.000 particles/kg dry matter. On the other hand, it is seen that the existing sludge treatment systems have not been successful in MP removal and urgent solutions are needed in this regard. Moreover, several recent studies have shown that MPs in sludge have adverse effects on anaerobic digester efficiency depending on the type, size and dose. It is of great importance to reveal and eliminate this negative effect in anaerobic digesters that produce renewable energy (biogas), reduce the amount of sewage sludge and offer a sustainable sludge management alternative. On the other hand, it is known that plastics not only have a very durable structure, but also show changes in their basic properties as a result of exposure to various stressors such as acid, alkali and heat treatments, and thus become more suitable for degradation. in the next stages. Based on the original finding that the separation methods aiming to increase the biogas production efficiency by disrupting the bulk structure of the sewage sludge show great similarities with the stress factors mentioned above, the project aims to monitor these processes together in terms of MPs by integrating the degradation process. conversion methods to anaerobic digesters. This unique project, which has not yet been studied in the international literature, aims to examine three different types of MP (Polyethyleneterephthalate, Polycarbonate and Polypropylene) in these processes, which are common in sludge but whose effects have not yet been investigated.
The work packages (WP) and their completion status in the project are given below.
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Work Package No |
Work Package Name |
Work Package Goal |
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1 |
Implementation of different disintegration alternatives and determining their effectiveness |
The two main objectives of this WP are to determine the most effective conditions for sludge degradation by applying different disintegration alternatives in sludge samples with different polymer properties, with different conditions, and to develop a method for the measurements of possible leaching additives from 3 different plastics selected for study. |
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2 |
Determining the effects of disintegration methods on MPs |
The two main objectives of this WP are to determine the properties of MPs with quantitative parameters, to reveal the effects of the treatment sludge disintegration methods applied on MPs, and to determine whether there is phthalate and BPA leakage from plastics during these processes and, if so, the leaking concentrations. |
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3 |
Determination of the effects of MPs in mesophilic digesters |
The objective of this WP is to determine the effects of MPs on digester performance in mesophilic anaerobic digesters established with disintegrated and untreated MPs and sewage sludges. |
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4 |
Determination of the effects of MPs in thermophilic digesters |
The objective of this WP is to determine the effects of MPs on digester performance in thermophilic anaerobic digesters established with disintegrated and untreated MPs and sewage sludges. |
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5 |
Determination of the fate of MPs in mesophilic and thermophilic digesters |
The objective of this WP is to determine the fate of MPs in reactors by analyzing polymer properties for MPs from all reactors that have completed the anaerobic digestion process (mesophilic and thermophilic). |
The project started on October 1st, 2021 and will last for three years in total.
- The first year of the project was completed on October 1st 2022. WP-1 and WP-2 have been mostly completed and preliminary studies have been started for WP-3 and WP-4.
- The second year of the project was completed on October 1st 2023. WP-1 and WP-2 have been completed, more than half of WP-3 and WP-4 have been finished and works for WP-5 have started.