Nouvelle normalisation allemande des filtres plantés pour le traitement des eaux usées domestiques | The new draft German constructed wetland guideline for treatment of domestic and municipal wastewater

The German guidelinefor the dimensioning, construction, and operation of constructed wetlands for biological treatment of domestic and municipal wastewater, which last published in March 2006, has recently been revised. The guideline applies to small wastewater treatment systems of less than 50 Person Equivalents (PE), municipal treatment plants up to 1.000 – 3.000 PE (with combined or separated sewers), treatment systems which use constructed wetlands as a polishing step, and small wastewater treatment systems which are operated seasonally (summer months only).The revision is based on a wide range of experience gained in recent years in the use of treatment wetlands in Germany and in Europe. Previous to the revisions, the proposed changes were discussed in a public hearing in Potsdam, Germany in January 2014. The final revisions were released for public review in October 2015. The finalized document is anticipated to be put into effect in April, 2016. A number of constructed wetland designs appear for the first time in the new guideline. Two-stage unsaturated vertical flow gravel filters which receive raw wastewater in the first stage (based on experience in France) as well as two-stage unsaturated vertical flow filters receiving primarytreated wastewater (based on experience in Austria) are now included. The revisions also include new dimensioning for unsaturated vertical flow filters with lava sand as the main treatment media, as well as aerated treatment wetlands, both as secondary treatment steps. Recommendations are also provided for seasonally operated constructed wetlands, as well as constructed wetlands for graywater treatment. With the publication of the new guideline, horizontal subsurface flow constructed wetlands are no longer supported as a secondary treatment stage in Germany, and are recommended only as a tertiary or polishing stage. Existing horizontal subsurface flow wetlands are allowed to continue operation, provided the systems are not hydraulically or organically overloaded, and that they continue to receive routine operations and maintenance. This presentation will outline the key points of the newly revised DWA-A 262 German constructed wetland guideline.