Peat from Northern Sweden is a natural filter material which efficiently absorbs oil, heavy metals and other pollutants from water. Axon miljöteknik (Axon Environment Technique) develops peat based filter solutions for applications such as boat washing facilities and fuel filling stations. The used peat can be combusted as a fuel.

”Our environmental filter is a natural water purifier that absorbs oil and heavy metals. We are using peat from Northern Sweden, which is especially good at absorbing contaminants from water. Peat that is formed north of the Arctic Circle has special properties and absorbs oil very well”, says Per Axelsson, CEO of Axon Miljöteknik (Axon Environment Technique).

”One liter of granulated peat is capable of absorbing halv a liter of oil. Besides the groundwater protection, the peat has an additional advantage in that it can be combusted as a fuel when it is discarded”.

The peat absorbs pollutants

Transformatorn (A) innehåller olja och är därför placerad på en uppsamlingsyta (B). Regnvatten med eventuellt oljespill leds till filteranläggningen som består av fem moduler med värmebehandlad torv (C). Det renade vattnet leds till en pumpgrop (D) och återförs till omgivningen via en stenkista.

The transformer (A) contains oil and is placed on a surface to gather runoff (B). Possibly contaminated rain water is diverted to the filter system: five modules containing thermally treated peat (C). The purified water is collected in a pit (D) before being brought to the environment through a french drain.

”Our first filter was developed in the 1990s, and was designed to handle diesel spillage at fuel filling stations. The contaminated water is gathered on a surface which diverts it to a filter pit. In the pit, the water passes through four layers of peat which absorb the contaminants. What comes out on the other side is basically pure water; tests have shown that the system achieves a 99.98 percent purification of diesel contaminated water”, Per says.

”We have filters for permanent installation above ground, underground, indoors and outdoors, as well as a number of mobile solutions. We have also developed auxiliary products to optimize the performance of the peat filters: technical shelters, pump wells, three chamber septic tanks, surfaces, gutters, simple alarm devices for oil and advanced technical equipment for detection and documentation. Our customers include energy companies with transformers that contain oil, fuel refilling stations and other places where water and soil contamination could be an issue”, Per Axelson says.

The company utilizes an oil absorbent called Axon Miljöfilter Absorbent AFX. The peat is thermally treated and contains about ten percent water, which is low compared to other absorbent materials. The heat treatment creates a layer of resin on the surface of the 2 – 8 mm peat granules. The hydrophobic resin prevents water from entering the granules. Only organic compounds can penetrate it, and these are absorbed within the granules.

Besides absorbing oils and other organic compounds, the peat functions as an ion exchanger, trapping heavy metals in the filter.

”The absorbent is easy to handle when it is saturated. It doesn’t get soggy or messy, and very little can be leached out. Since the thermally treated peat is free from chemical additives, the material can be combusted for energy or converted to compost at the location. The energy content is high and the ash content is low, making it cost-efficient. The possibility of on-site destruction is an important benefit, reducing both environmental impact and transport costs. Naturally, incineration and composting still have to be performed at proper facilities licensed to handle this kind of material”.

Environment-friendly boatwash

Tvättplats för båtar med spolplatta och teknikbod från Axon.

A boatwash with Axon’s filter system.

The washing of boats painted with antifouling paint on the bottom is a well known environmental issue. Antifouling paints contain environmental toxins which contaminate the wash water. It is not unusual for the seabeds around the hardstands and boat storages to become void of life. A massive amount of research and development is dedicated to find a replacement for the toxic antifouling paints.

Boatwash facilities are facing strict regulations, both from the EU and Swedish authorities, to keep the environmental impact at a minimum.

”We began work in 2012 to develop a filter system for boatwashes, starting out with our proven peat filter. We realized that a secondary carbon filter was needed to get rid of TBT, a chemical compound based on tin, and Irgarol, a copper compund. Both of these biocides are already banned, but they are still present in the water from boatwashes, leaching from older layers of bottom paint”.

”A scientific evaluation of the performance of the new filter system in a real-world setting has been performed, in collaboration with Mälardalen University. The results verified that large amounts of TBT, Irgarol, copper and zinc are present in the pump wells at the boatwashes. The positive conclusion of the analysis was that our filter system released water with a level of contamination well below the stated limits. The system is now deployed in a number of ports in Sweden and Norway and the facilities perform very well, with minimal maintenance requirements”, Per Axelson says.

The article was published in September 2016.