Material and energy recovery from sewage sludge

Currently, sewage sludge is used for agricultural purposes by direct land application or as compost, (co-)incinerated or landfilled. In the Czech Republic, land application or composting is the predominant material use. In contrast, in Western European countries (e.g., Germany, Austria, Switzerland, the Netherlands, Belgium), incineration or co-incineration predominates. This approach is mainly based on concerns about environmental contamination by pollutants contained in sludge, such as heavy metals, microplastics, pathogens, organic pollutants (PAHs, per- and polyfluorinated substances (PFAS), flame retardants, pharmaceuticals, hormones or endocrine disruptors, etc.). These substances are removed during incineration and the resulting ash from mono-incineration is rich in phosphorus, a critical resource for the EU. For this reason, some countries, such as Germany, Austria and Switzerland have already made it mandatory to recover (regenerate) phosphorus from the ash from the incineration of sewage sludge or directly sewage sludge itself.

The team of Associate Professor Pohořelý is working on the thermochemical treatment of sewage sludge, in particular the pyrolysis and incineration of sewage sludge with subsequent use of the solid products of the processes. The results of the research were successfully used in collaboration with HST Hydrosystémy, Ltd. to optimise the operation of a commercial unit for pyrolysis of sewage sludge at the Trutnov – Bohulavice wastewater treatment plant. The practical conclusions were that pyrolysis should be carried out at a temperature of at least 500°C (with temperatures above 600°C during nominal plant operation) in order to achieve sufficient transfer of sludge energy to the primary pyrolysis gas, which also serves to heat the pyrolysis itself and to pre-dry the sludge, remove any organic pollutants, pathogens and microplastics present, and create sufficient porosity in the sludge-char.

Our results contribute to the modification of European and Czech legislation concerning the production and use of sludge-char in agriculture. For example, thanks to the cooperation in the Czech Republic, sludge char produced at the Trutnov WWTP has been removed from the waste catalogue and certified by the Central Institute for Supervising and Testing in Agriculture as a soil amendment (Karbofert T1). Members of the team also act as scientific experts in the discussions led by the group for pyrolyzed sludges of the European Biochar Industry Consortium (EBI), which is tasked with initiating the modification of Regulation (EU) 2019/1009 of the European Parliament and of the Council laying down rules on the making available on the market of EU fertilising products by creating its own category of constituent materials for pyrolysed sewage sludge.

In addition, the group led by Associate Professor Pohořelý is working on the following topics

• Fluidised bed incineration of sewage sludge with the possibility of using the ash to recover phosphorus and other useful raw materials.
• Legislation in the field of sewage sludge management at national and international level, e.g. in specific collaboration with scientific colleagues in Japan.
•  Removal of per- and polyfluorinated substances (PFAS) and organic fluorine from sewage sludge by pyrolysis at laboratory and application scale at the Bohuslavice - Trutnov WWTP in cooperation with the Institute of Microbiology of the CAS

Projects

Articles

1. Matsunaga, T., Homma, R., Oshita, K., Husek, M., Takeuchi, H., Nishimura, F., Takaoka, M. National survey of 30 per-and polyfluoroalkyl substances (PFAS) in dewatered sewage sludge. Journal of Japan Society of Civil Engineers  80, 25, (2024). https://doi.org/10.2208/jscejj.24-25006 (Scopus).
2. Wickramasinghe, N., Vítková, M., Zarzsevszkij, S., Ouředníček, P., Šillerová, H., Ojo, O.E., Beesley, L., Grasserová, A., Cajthaml, T., Moško, J., Hušek, M., Pohořelý, M., Čechmánková, J., Vácha, R., Kulhánek, M., Máslová, A., Komárek, M. Can pyrolysis and composting of sewage sludge reduce the release of traditional and emerging pollutants in agricultural soils? Insights from field and laboratory investigations. Chemosphere 364, 143289, (2024). https://doi.org/10.1016/j.chemosphere.2024.143289. (WoS, JIF 8.1 /2023/, Q1/D1*)
3. Řimnáčová, D., Bičáková, O., Moško, J., Straka, P., Čimová, N. The effect of carbonization temperature on textural properties of sewage sludge-derived biochars as potential adsorbents. Journal of Environmental Management 359, 120947, (2024). https://doi.org/10.1016/j.jenvman.2024.120947. (WoS, JIF 8.0 /2023/, Q1/D1*)
4. Hušek, M., Semerád, J., Skoblia, S., Moško, J., Kukla, J., Beňo, Z., Jeremiáš, M., Cajthaml, T., Komárek, M., Pohořelý, M.. Removal of per- and polyfluoroalkyl substances and organic fluorine from sewage sludge and sea sand by pyrolysis. Biochar 6, 31, (2024). https://doi.org/10.1007/s42773-024-00322-5. (WoS, JIF 13.1 /2023/, Q1/D1*).
5. Mitzia, A., Böserle Hudcová, B.B., Vítková, M., Kunteová, B., Hernandez, D.C., Moško, J., Pohořelý, M., Grasserová, A., Cajthaml, T., Komárek, M. Pyrolysed sewage sludge for metal(loid) removal and immobilisation in contrasting soils: Exploring variety of risk elements across contamination levels. Science of the Total Environment 918, 170572, (2024). https://doi.org/10.1016/j.scitotenv.2024.170572. (WoS, JIF 8.2 /2023/, Q1/D1*).
6. Sikarwar, V.S., Mašláni, A., Van Oost, G., Fathi, J., Hlína, M., Mates, T., Pohořelý, M., Jeremiáš, M. Integration of thermal plasma with CCUS to valorize sewage sludge, Energy 288, 129896, (2024). https://doi.org/10.1016/j.energy.2023.129896. (WoS, JIF 9.0 /2023/, Q1/D1*).
7.  Hušek, M., Homma, R., Moško, J., Pohořelý, M., Oshita, K. P-recovery versus current sewage sludge treatment policy in the Czech Republic and Japan. Clean Technologies and Environmental Policy, 26, 1883–1899 (2024). https://doi.org/10.1007/s10098-023-02679-w. (WoS, JIF 4.2 /2023/, Q2).
8. Hušek, M., Moško, J., Pohořelý, M. Sewage sludge treatment methods and P-recovery possibilities: Current state-of-the-art. Journal of Environmental Management 315, 115090, (2022). https://doi.org/10.1016/j.jenvman.2022.115090. (WoS, JIF 8.910 /2021/, Q1).
9.  Moško, J., Jeremiáš, M., Skoblia, S., Beňo, Z., Sikarwar, V.S., Hušek, M., Wang, H., Pohořelý, M. Residual moisture in the sewage sludge feed significantly affects the pyrolysis process: Simulation of continuous process in a batch reactor. Journal of Analytical and Applied Pyrolysis 161, 105387, (2022). https://doi.org/10.1016/j.jaap.2021.105387. (WoS, JIF 6.437 /2021/, Q1).
10. Moško, J., Pohořelý, M., Skoblia, S., Fajgar., R., Straka, P., Soukup, K., Beňo, Z., Farták, J., Bičáková, O., Jeremiáš, M., Šyc, M., Meers, E. Structural and chemical changes of sludge derived pyrolysis char prepared under different process temperatures. Journal of Analytical and Applied Pyrolysis 156, 105085, (2021). https://doi.org/10.1016/j.jaap.2021.105085. (WoS, JIF 5.541 /2020/, Q1).
11.  Moško, J., Pohořelý, M., Cajthaml, T., Jeremiáš, M., Robles-Aguilar, A.A., Skoblia, S., Beňo, Z., Innemanová, P., Linhartová, L., Michalíková, K., Meers, E. Effect of pyrolysis temperature on removal of organic pollutants present in anaerobically stabilized sewage sludge. Chemosphere 265, 129082, (2021). https://doi.org/10.1016/j.chemosphere.2020.129082. (WoS, JIF 7.086 /2020/, Q1).
12. Moško, J., Pohořelý, M., Skoblia, S., Beňo, Z., Jeremiáš, M. Detailed Analysis of Sewage Sludge Pyrolysis Gas: Effect of Pyrolysis Temperature. Energies 13, 4087, (2020). https://doi.org/10.3390/en13164087. (WoS, JIF 2.702 /2019/, Q3).
13. Hartman, M., Čech, B., Pohořelý, M., Svoboda, K., Šyc, M. Slow-rate devolatilization of municipal sewage sludge and texture of residual solids. Korean Journal of Chemical Engineering 38, 2072–2081 (2021). https://doi.org/10.1007/s11814-021-0847-8. (WoS, JIF 2,9 /2023/, Q2).
14. Pohořelý, M., Picek, I., Skoblia, S., Beňo, Z., Bičáková, O. Způsob a zařízení pro energetické zpracování sušeného čistírenského kalu. Method and Device for Energy Processing Dried Sewage Sludge. Pat. No. 308451. Patented: 15. 7. 2020.