Environment

Organic filter to clean up Finnish holiday home wastewater

13/03/2009
Organic filter to clean up Finnish holiday home wastewater

Legislation limiting discharge of untreated wastewater from Finnish holiday homes not connected to municipal sewage systems prompted the development of an organic wastewater filter.

Improving the state of inland waters and the Baltic Sea were challenges identified by the Finnish roadmap for the implementation of ETAP. Approximately a million Finns spend part of the year in holiday homes not connected to municipal sewage systems. Wastewater from these secondary residences is a considerable source of phosphorus loading in Finnish water courses, second only to agriculture.

Moreover, the organic matter consumes the oxygen resources of water bodies. Visible signs of eutrophication are algae, increased reed and rush growth at the shore line, obstructive vegetation in ditches and changes in fish populations. In small and sensitive water bodies, even a small wastewater load can lead to a considerably deterioration.

The treatment of wastewater in rural areas will be improved greatly thanks to Government legislation, which has set minimum standards for wastewater treatment and the planning, construction, use and maintenance of treatment systems in rural areas with no centralised sewerage system. The requirements already apply to new buildings; treatment systems for existing buildings must be upgraded to the new standards by 2014.

However, as many Finnish holiday homes are in places where it is difficult or even impossible to install a filter for ‘greywater’ – the wastewater from domestic processes such as dish washing, laundry and bathing – underground, an alternative solution had to be found. With help from public funding, Finnish company Biolan Oy has developed an organic moss-based filtration system to meet these new standards.

On-site wastewater treatment

The new greywater filter is an on-site treatment unit specifically designed for holiday homes. It is designed to clean water that has been used for washing up, bathing and laundry. To cope with Finland’s harsh winter climate, the filter systems are installed in a heated space or equipped with a heating cable. The units are suited to rocky plots, as well as those with high groundwater levels, and have the added bonus of not requiring separate septic tanks.

The filter system uses Warnstorfia moss, which retains its moisture even when the system is not in use. Micro-organisms that grow on the surface of the moss filter out the impurities and nutrients in wastewater both mechanically and biologically. The unit is easy to install, easy to use and, as it is an above-ground system, easy to service. Moreover, the organic filter material can be replaced without difficulty, and can be composted after use.

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