As constructed wetlands are particularly can best be utilized in areas with only a few thousand inhabitants due to the required floor space it can ideally be realized in large states with a scattered settlement structure and a postponed demand regarding the wastewater disposal modernisation. The joint project therefore included research in systems in Brandenburg, Saxony, Bavaria and Lower Saxony.

The joint project furthermore fostered the development and usage of biotechnological procedures. The know-how advantage thus accomplished is pin-pointably be used as an economical advantage for the export. The usage of constructed wetlands is especially fitted as a product for small and medium businesses with a strategic orientation towards Eastern Europe. Corresponding contacts and market explorations have been made as part of the project.

Desciption of the focal points of the aid programme and the specialized work groups

Despite the fact that the processes of nitrogen conversion are basically understood the pin-pointed control of the processes as well as the exact dimensioning of the required steps still require some development. It has been found that while reliable nitrification is possible in vertical filters this is not the case in horizontal filters. The nitrification process in these is usually incomplete while the nitrificated nitrogen is laso mostly denitrificated. This led to the neccessity of a combination of vertical and horizontal filters or the development of equally effective procedure steps. The desired ammonium concentration for improving the water quality had to be determined for several selected environmentally sensitive bodies of flowing water. Feeding the wastewater purification system with wastewater is the only way to determine in a real life setting the control possibilities of the processes within it . Hydraulic control concepts for optimizing the biological purification performance have been developed. Furthermore control options for the compound system pond filter and soil filter level have been explored which, in critical times for the waters, make it possible to stop the wastewater flow-off through its hydraulic buffeting possebilities.

According to Hagendorf and Hahn (1994) constructed wetlands eliminate a large percentage of the faecal indicative germs. However investigations concerning appearance and where-abouts of infectuous germs (facultative pathogenic germs) are missing, thus making a complete judgement on the risks regarding epidemic diseases impossible. When taking sanitary precaution into consideration such investigations are urgently needed, since the construction and operation of constructed wetlands in a large diversity of set-ups has increased significantly. These flow-offs are also often fed into bodies of water which are hydraulically weak and sensitive to ecological or environmental burdens (headwaters of brooks, swimming waters, drinking water river dams) or seep into the ground and underground waters. This made it necessary to formulate hygienical and bacteriological standards for system locations with a special health and environmental protection function in the interest of an all encompassing water protection.

The phosphor elimination capacity can also be comparable to large-scale water purification systems with a chemical level if a suitable filter substrate is used. This is especially important for the Northern German flat land (Mecklenburg-Vorpommern, Brandenburg, Schleswig-Holstein and Lower Saxony) since these are equipped with relatively few overground bodies of water. Therefore many drainage systems feed into slowly flowing or non-moving waters such as lakes, in which the eutrophication is considerably directed by phosphor as a growth limiting factor. The systems with combinations of vertical filters and horizontal filters as well as an exchangeable soil filter, which are to be inspected by AKUT, lie within the drainage areas of non-moving waters or a drinking water river dam. Especially within the drainage area of the drinking water river dam there is a need for purification results (regarding phosphor reduction) and nitrogen as well as germ elimination which significantly exceed the legal requirements.

Blocking of the water bearing pore spaces (colmation) can greatly reduce the project life and operating safety of constructed wetlands. The different factors` complex inductions which occur in this context, such as sedimentation, biological exchanges and ground structure formation, were revealed and understood regarding their causes through morphological, ground physical and microbiological investigations (IFB). Because of the divers types of colmation the joint partners were working together in order to develop methods and instructions which will help avoid these complications through appropiate operating procedures. In order to do this they of course took the individual operation and system circumstances into account.

Rainwater from composting plants

Since most of the currently operated constructed wetlands were designed for the purification of municipal wastewater extensive experiences with the treatment of special wastewaters are still missing. The project of ÖKOLOG and the TU Munich was designed to evaluate the efficiency of constructed wetlands in purifying rainwater from compost plants. The possebility of eliminating dangerous substances in a vertical filter is being researched as well as nitrogen limit values which are to be observed.

User′s Manual

A comprising interpretation of flow-off data and operation experiences did not exist for constructed wetlands > 50 inhabitants in any predominantly german speaking area. These experiences were collected and evaluated in a user´s manual. This will help to pass on the updated data to the operators and planning engineer bureaus. Furthermore a CD-ROM has been published which makes information regarding wastewater types, treatment techniques, filter materials, decomposition results, operation disorders and corresponding remedial measures as well as construction and operating costs available in form of a database with the appropiate search options for professionals as well as all other interested people (citizens, politicians, government).

Project management

A cooperative research project´s successful organization and realization requires a professional project management as well as effective communication between the project partners. This goal was supposed to be accomplished by this part of the project. The project also gained publicity through professional team meetings, status seminars and press conferences.

Public relations

One of the joint project´s main goals was to present and recommend the use of as well as the technical further development of plant water purification systems as a cost effective technology which protects the environment. This should be done not only to a circle of experts but also for the general public. The public relation activities planned by the project management had to be supported and expanded by further activities appealing to a broad range of potential participants. For this purpose several work shops, an international status seminar in St. Marienthal, a specialist symposium in connection with the UTECH Berlin and a final symposium (partly with excursions) was organized in connection with the cooperative research project.

Poland Contact Board

Wastewater purification techniques which have taken nature as their example and mainly function on a non-technical basis, especially constructed wetlands, are economically interesting for application in rising Eastern European countries also. It was the task of another project to set up contacts to regional authorities in Poland as well as to provide start-up application counseling for vegetated soil filters. The goal of the project was a market inquiry in regions close to the border to prepare a technology transfer.