Naturally aerated trickling filters have been a mainstay of biological wastewater treatment for decades in both municipal and industrial sectors. Initially using blast furnace slag as the carrier, they worked well for BOD reduction and nitrification, but had a large footprint. When it was discovered that the biofilm would attach to plastic surfaces, synthetic media rapidly became the norm, due to their higher surface area and voidage. The shapes of these carriers developed in complexity from simple pipe sections to multi-finned cylinders to maximise the specific surface area.

We have been at the forefront of the development of media technology, producing high surface area, high voidage filter media. High voidage allows the access of air to all the surfaces while minimising hydraulic resistance allowing existing trickling filters to handle higher flows and loads and reducing the required footprint for new builds.