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View of the courtyard, photographed in 1990s.
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View of the courtyard, photographed in 1990s.
ib-kraft.de

‘Block 6‘ is a building complex at the Dessauer Straße, south-east of the Potsdamer Platz in Berlin’s Kreuzberg district. The block was developed as part of the International Bauaustellung, IBA Berlin 1987. As environmental awareness increased in the 1970s, IBA also sought ways to make urban life environmentally friendly. In the Block 6 eco-project, it succeeded in changing standards and perspectives. The project shows that decentralised drainage concepts with constructed wetlands are possible even in inner-city locations and with inner-city density.

Condition of Block 6 before IBA 1984-87

Block 6 is located in Kreuzberg, in the southern part of the former Friedrichstadt - Bernburger Straße 22–26 / Dessauer Straße 9–14. Before the war the block housed the old philharmonic hall, which was destroyed during the war. After the war, the entire site except for one building was vacated. The International Building Exhibition (IBA) took place in the 1980s and designed the construction of 106 apartments in six new buildings.

Condition of Block 6 after IBA 1984-87

‘Block 6‘ after IBA 84/87 consisted of an old building and a residential complex that was built in the 1960’s, a further 106 flats of the six new residential buildings and quite centrally the grey water constructed wetland plant comprising 900 square meters of in the inner courtyard with decorative bathing ponds. The project was something really special at the time and a construction-technical and environmental experiment for the city of Berlin - to treat waste water without chemical means and subsequently re-use it within the buildings.

Focus areas and implementation

The concept consisted of a combination of nine sub-concepts:

1. Saving drinking water

Use of the currently available water-saving technologies, such as 4-liter toilets or 6 liter toilets with the possibility of interrupting the flushing current; Flow restrictors on shower fittings; Washstands and sinks; apartment water meter.

2. Near-natural wastewater treatment

The cleaning of the gray water (shower, bathtub, vanity, washing machine, kitchen sink) takes place in

a wastewater treatment plant in the courtyard of the block. The later phase also envisioned the purification of faecal water.

The pre-treatment plant has two outlets of 12kbm each, in which the whole greywater is led by 76 residential units, whereby the settling sludge is removed twice a year.

From there, the pre-cleaned wastewater flows in a natural gradient through the four identical planted collection pits of the sewage treatment plant.

It flows horizontally across the entire width of the filter basin, variable water level is below the substrate. The wastewater then is in the central axis, collected and then fed to an approximately 100 square meter pond, the Schönungsteich. This is the only part of the facility that is fenced, since direct contact with 'waste water' would be possible there.

3. Heat recovery

Another facility that was envisioned but not put into operation for economic reasons was the heat recovery from the gray water. Large heat exchange plates in the central waste water collecting tank (Emscherbrunnen) installed over insulated pipes with a brine-water heat pump connected. The waste water heat from the 76 residential units was to enable hot water generation for 20 residential units.

4. Rainwater treatment

For rainwater retention and improvement of the microclimate, 50% of the roof areas were extensively landscaped. The excess rainwater was centrally collected in planted vertical filters (filter area 80 sqm) and cleaned in a separate system on the edge of the gray water purification plant.

It is then led into an approx. 1,000 sqm rainwater pond sealed with clay at three different points in order to achieve a gentle pond flow. The natural designed rainwater pond encloses the sewage treatment plant completely.

5. Groundwater enrichment

Another water cycle is closed by returning the excess purified wastewater to the groundwater. For this purpose, a groundwater enrichment plant with a size of 100 square meters was installed at a frost-free depth.

6. Drinking water substitution

The cleaned gray water is taken from the pond and used for the toilet flushing and irrigation. For this purpose, a second pipeline network made of corrosion-resistant PE and VDPE pipes is installed in the buildings.

A 2,000 liter process water tank and a pressure booster system were installed in the central operating cellar. If there is a shortage of water, process water can be fed into the tank.

7. Landscape design and local recreation

The premises for the open space planning were the creative integration of the wastewater treatment plant, extensive closeness to nature and ecological landscaping, great variety of experiences of the design elements as well as furnishing of tenant gardens.

The sewage treatment plant and the rainwater pond are designed so that they upgrade the interior of the block. The rainwater pond has a water play area for children, the wastewater treatment plant is accessible via a system of walkways/bridges, the biotope at the rainwater pond and groups of trees offer plenty of experience and closeness to nature. Elaborate play equipment was therefore deliberately avoided.

The retaining walls of the tenant gardens and other jumps in the terrain were included. Gambion technology of mesh work filled with recycled building material helped in reusing the rubble from the old foundations. The entire open area of Block 6 provided a diverse flora and fauna, natural, ecological and recreational possibilities for the tenants.

8. Waste concept

The waste concept includes: user information for waste prevention, separate collection systems for waste and valuable materials, two composting pits for the organic waste, separate collection of household and small chemicals in the yard of the block.

In the kitchens, systems for separate waste collection according to four fractions have been installed and tested in Berlin for the first time: crumpled paper, organic waste, plastics / metal materials / textiles, residual waste. The systems were mostly by the tenants - improved several times and saw a high level acceptance. Glass and newspapers are collected separately.

9. User concept

The user concept included a user program and a psychological one accompanying research. The latter examined the interactions between the ecological concepts and user behavior, at the same time explored what measures to take to ensure favorable conditions to create a success story for the project and what impact the project has on the neighborhood. The user program conveyed and promoted information and motivation for the integrated and holistic approach of the project. There were campaigns, seminars and Q&As with the specialist planners involved.

Results of the ECO project

The project was able to show that drinking water consumption is reduced by a third, and even by half if gray water is used. That is about 80 liters per day and person.

Years of increase in the cost of drinking water, most of the measures envisioned already showed economic efficiency. They were therefore in 1990 the Berlin housing subsidy guidelines.

The wastewater treatment plant though did not bring out the desired quality. This was due to the water-saving behavior of the residents. Due to less water in the plant, the greywater polluted as much as normal municipal wastewater. This called for improvisation, the number of connected apartments was reduced.

Because of the inadequate quality of the cleaned gray water, the groundwater enrichment as well as the drinking water substitution could not be implemented.

The rainwater pond enabled the rainwater on the property to be completely retained. There was no rainwater runoff in the public channel. The hygienic quality of the pond was continuously monitored and always met the prescribed EC limit values ​​for swimming pools. The rainwater pond was developed and enjoyed as a biotope along with the whole outdoor facility. The courtyard saw high acceptance among the residents, and it was also reflected in the care of the pond by the residents.

The most important result was the positive reaction of the residents to the integrated water concept. In 1989, the residents founded the Eco-Social Living Association, which has played an important role in the project and has co-determined from project-related decisions up to working on site. Also, ecological standards common today were tried and implemented here for the first time: Waste separation, extensive green roofs and water saving devices in all apartments.

In 1987, the block became a pilot project of the founding of “Experimental Residential and Urban Development” (EXWOST) programme for ecological urban renewal with federal and state funds. Due to inefficiency and malfunction the treatment plant was shut down by the owner in 1993.

Closure of the plant and later initiatives

However, the State of Berlin and the owner indeed wanted to ensure that the plant would remain in place as a “technical monument.” The goal of the State of Berlin along with the owner of the inventory of the facility was to secure and optimize the “technical monument” coupled with a new innovative water concept for process water use and rainwater management, restore operations and handle management under economic conditions, minimizing operating costs for tenants.

Further improvements in 2006

The grey water treatment plant at Block 6 was technically re-designed and further developed in 2006. An industrial water house was built in an ecological wooden construction at the foundation of the former water collection pond, “Schönungsteich” of the sewage treatment plant in the block courtyard. Since then, the gray water of about 250 people has been mechanically and biologically processed to bathing water quality and reused for flushing the toilets and watering the tenant gardens. The rainwater from the 2,350m² roof area and 650 m² sealed area is now discharged into the original water treatment plant. The microclimate is improved by the evaporation of the plants.

TU Berlin’s Roof Water Farm in 2013

The start of the research project ROOF WATER-FARM by TU Berlin was a natural further development of the location. In 2013, TU installed the ROOF WATER-FARM demonstration system and test track in the courtyard of Block 6 in order to further develop the separation and reuse of the building-related wastewater flows. The technical components of research become visible and tangible in the process water house with wastewater treatment system and in the aquaponic greenhouse. It included;

-the treatment of greywater to process water up to the tested hygienic quality.

-the analysis of relevant micro pollutants in wastewater (drug residues, e.g. diclofenac, ibuprofen, carbamazepine)

-the cultivation of vegetables and the rearing of fish (hydroponics , aquaculture ) and

-the production of fertilizer solution from black water for hydroponic plant cultivation.

The demonstration system and test track enable the experiment at Block 6 to provide the researchers with,

-procedural and static data for the application of ROOF WATER-FARM technology in greenhouses on the roofs of the city.

-Values ​​for sustainability considerations and

Key data for the development of operator models for commercial and non-commercial operation and product marketing.

This data is used for further multiplication and implementation of the project on inner city rooftops or courtyards allowing Block 6 to still hold the status of an ecological prototype that it has always been. As a result of the efforts of everybody involved, the plant and its urban ecological model character have been preserved. According to the Senate Department for Urban Development, it is now Berlin’s only pilot project for ecological building featuring water recycling.

Dessauer Straße / Bernburger Straße