At peat production areas, the best available techniques (BAT) are always defined on a case-by-case basis taking into account the particular conditions at each production area and the remaining operational time. Water treatment using overland flow or chemical purification is the best available technique for peat production.
The feasibility of implementing year-round overland flow has to be researched irrespective of the size of the production area. At new production areas, water treatment must be at least be as effective as overland flow. It is not always possible to use overland flow at areas in production, because no suitable areas for it to operate are available. Then water treatment has to be enhanced by other methods, e.g. vegetation fields and reservoirs or chemical purification. The best available technique for these production areas could also be a combination of several different methods.
From the field channel at the peat production area the water is led to a sedimentation pond, where the majority of the sludge separates by settling at the bottom of the pond. From here the water is led to an overland flow field, vegetation field or wetland, which effectively bind suspended solids and nutrients.
Chemical purification is suitable for areas where there is no area suitable for overland flow or other enhanced methods. Chemical purification generally makes economic sense for production areas larger than 150 ha.
Sludge pockets, sludge traps, sedimentation ponds and run-off peak control are base-level water treatment methods in use at peat production areas. The water is treated in these prior to overland flow fields or wetlands.
Vapo has set itself the target of installing the best water treatment at all production areas by the end of 2014. Vapo has also installed the first continuous equipment to measure the quality and quantity of run-off water to provide data on the load of suspended solids and dissolved organic matter (humus) every day of the year.
80% of Vapo’s mires are covered by BAT, and 11,000 hectares, or 20% of areas, will get enhanced treatment or will be closed down. The move to 100% BAT will start by planning water treatment structures on a site-by-site basis. The first enhancement plans will be submitted for statement to the regional Centres for Economic Development, Transport and the Environment in summer 2012. When the centres have delivered their statements, construction will start at the sites.