Pasteurization – Thermal Hygienisation of Sludge
Sludge pasteurisation prior to anaerobic digestion is a thermal process in which sludge is heated to a defined temperature, typically 70–75 °C, and held for approximately 30–60 minutes to inactivate pathogens, undesirable microorganisms, and enzymes.
The purpose of pasteurisation is to improve the biological safety and quality of sludge, enhance digestion efficiency, and eliminate pathogenic microorganisms.
1. Objectives of Pasteurisation
- Hygienisation – reduction of bacteria, viruses, and parasite eggs to levels required by sanitary regulations.
- Regulatory compliance – e.g. EU Class A sludge (Regulations 1069/2009/EC, 142/2011/EC) requires the elimination of Salmonella and reduction of E. coli.
- Safe agricultural use – minimisation of epidemiological risks.
- Facilitation of further treatment – improved conditions for anaerobic digestion or composting.
2. Pasteurisation Technology
Tank reactors with mixers are applied, where sludge is fully heated in heat exchangers and then transferred to the reactor for a minimum retention time of 30 minutes. The technology enables continuous system operation.
We apply heat recovery after pasteurisation and utilise waste heat from cogeneration engines for sludge heating in the pasteurisation process.
3. Advantages
- Effective pathogen reduction – achieving Class A hygienic standards.
- Safe agricultural utilisation of sludge.
- Improved susceptibility of sludge to further biological stabilisation.
We ensure that maintenance and servicing requirements are minimised, while our equipment is designed for durability and reliable operation. This significantly reduces operating costs while increasing process performance and efficiency.
As part of our equipment or complete process line selection, we provide an analysis of the current and forecasted conditions at the facility, along with the preparation of a tailored process design.