Regenerative Thermal Oxidation (RTO) from CTP Air Pollution Control GmbH can reduce emissions by up to 99.5 per cent.
CTP systems offer highly efficient exhaust air treatment for a wide range of industrial processes, whilst delivering maximum cost-effectiveness. Gaseous pollutants such as organic compounds, CO, NH₃ and odours are eliminated in a regenerative thermal process. Toxic and environmentally hazardous substances such as PCDD/Fs, PAHs, OHAPs and PFAS can also be reliably removed using CTP systems.
A new and innovative application for RTOs is the reduction of nitrous oxide emissions. Nitrous oxide is e.g. one of the most potent, yet often overlooked, greenhouse gases from wastewater treatment plants. It is chemically very stable, remains in the atmosphere for over 100 years and has a global warming potential being 250 to 300 times higher than that of CO₂. “The importance of reducing nitrous oxide from sewage treatment works is often underestimated, even though these emissions – primarily from the biological treatment stage – account for a significant proportion of CO₂ equivalents,” says Gerd Rabenstein, COO of CTP Air Pollution Control GmbH. For a long time, these emissions received little attention. However, as climate targets become more stringent, plant operators are increasingly focusing on targeted nitrous oxide abatement strategies.
RTO technology: An efficient solution for nitrous oxide reduction in sewage treatment works
CTP addresses this problem using Regenerative Thermal Oxidation: in the combustion chamber of the RTO system, nitrous oxide molecules are thermally decomposed into their constituent elements – nitrogen and oxygen – at high temperatures. “Catalytic approaches are subject to limitations due to catalyst poisoning and the resulting short operational lifetimes.,” explains Rabenstein. “With our robust solution, nitrous oxide can be almost completely eliminated.”
RTO systems are considered particularly flexible and can be individually optimised for parameters such as purification performance, energy efficiency or pressure drop. Thanks to regenerative heat exchangers, the systems also operate very energy-efficiently – when biogas is used as fuel, operation can even be made climate-neutral.
Innovative case study: ARA Bern – over 95 per cent reduction in nitrous oxide achieved
The ARA Bern wastewater treatment plant in Switzerland demonstrates just how efficiently the technology can be used in practice. The plant is one of the largest sewage treatment works in the country and has been using a specially designed RTO solution from CTP since August 2025. Prior to the implementation, more than 10,000 tonnes of CO₂ equivalents were emitted annually in Bern due to nitrous oxide emissions from the biological and digested sludge treatment. With the new technology, over 95 per cent of N₂O emissions can now be removed from the exhaust air.
The system installed features three ceramic heat storage units that operate in alternating cycles, enabling particularly efficient heat recovery. The solution was precisely tailored to the requirements of the sewage treatment works and integrates seamlessly into existing operations without disrupting the wastewater treatment processes. The effectiveness of the technology has also been confirmed by independent organisations: the Swiss Foundation for Climate Protection and CO₂ Offsetting ‘KliK’ supports projects aimed at reducing nitrous oxide emissions and regards the application in Bern as an exemplary project.
A compact solution for smaller exhaust air flows: the DeNitroBox
In addition to custom-designed large-scale systems, CTP also offers the DeNitroBox as a compact solution for smaller exhaust air flows. This plug-and-play system is housed in a 20-foot container and achieves N₂O reduction of up to 90 per cent whilst consuming minimal energy. At the same time, this compact RTO also achieves outstanding performance in reducing other gaseous pollutants. The containerised solution can be installed directly on site and offers a straightforward entry point into emissions reduction.
Visitors to ESS Expo 2026 in Birmingham, UK, (16-17 September 2026) are invited to experience CTP’s innovative technology for nitrous oxide reduction in wastewater treatment plants and learn about proven applications in the field. (Booth EN-J90)
Source: CTP Chemisch Thermische Prozesstechnik GmbH
