BHS technology used for the innovative HALOSEP recycling process

February 2022

The reference at a glance


Integration of the new HALOSEP process in the processing of incinerator bottom ash


Operating site

Copenhagen, Denmark




Waste incineration in power plants


Integration of specific filtration solutions into overall processes

The EU wants at least 50 percent of household waste to be recycled and the rest to be used as a source of energy in waste incineration plants. However, waste incineration produces ash – a hazardous waste contaminated with salts and heavy metals that must be disposed of in special landfills, which involves long transport routes and high costs. The Danish power plant operator Vestforbraending uses the HALOSEP technology developed and patented by the Swedish group Stena Recycling, a process solution that makes it possible to dispose of ash as normal waste. In this project funded by the European Union, technology from BHS-Sonthofen is used for two steps at once.

Treating fly ash produced during waste incineration is a multi-step process. First, it is mixed with the flue gas cleaning washing water, which leads to metals and salts being released from the ash. A BHS belt filter then filters the resulting suspension. After a further wash, the solid that remains is purified ash.

The process water used in the first step is treated further to recover both salts and metals. After the salt water has been separated, a BHS rubber belt filter with continuous vacuum filtration filters the suspension; the metals are left behind as solids. The process water can now be returned to the process.

This means that this new process (HALOSEP) for treating fly ash has two advantages: On the one hand, recyclable materials are recovered from the ashes, and on the other hand, the ashes are upgraded from hazardous waste. In the future, the processing should go so far that they can be used directly as an additive for building materials. BHS technology is also used in related processes, such as FLUWA.

BHS-Sonthofen not only supplied the technology, which needs to be robust and resistant to corrosion for this application, but also impressed the customer by the close cooperation in the preliminary stages above all: The filters were perfectly adapted to the new process following laboratory-scale tests at the customer’s site. The commissioning of the complete plant took place in a Vestforbraending waste-to-energy plant in early 2021.