Pyramid for ecological waste water treatment plant powered by electricity from photovoltaic cells.
The City of Kolding constructed an impressive decentralized wastewater cleaning operation and glass pyramid within a city block. The project was developed for an ecological waste water treatment plant as part of an urban renewal project in 1995.
It is an older pilot project, so the long term consequences can be seen.
Decentralized sanitation of wastewater is the most import element of the scheme. Blackwater and greywater are collected together inside the block by use of a normal sewer into a buffer tank. From there, the sludge is settled out, which is removed an treated in the municipal WWTP, so not all parts of the wastewater stream are treated in the neighborhood. The remaining liquid fraction of the wastewater passes through a series of reactors for aeration, clarifying, and purification with ozone and ultraviolet light. After this last step, the cleaned wastewater enters the pyramid, where it was meant for irrigation and supporting tilapia fish. However, both of these functions have ceased. Finally, after the pyramid, the wastewater is infiltrated into surface water. Besides drinking water, rainwater is harvested from building roofs. It flows down gutters into a storage tank inside the block. From there it is pumped through a simple fabric filter into the homes for toilet flushing and a washing machine. To support the decentralized wastewater system, a bank of solar PV panels were installed above a parking area. However, it does not provide enough energy to compensate for the entire operation. Inside the block, the inhabitants have drop-off facilities for mixed refuse, glass, paper, ‘problem refuse’ (chemical, metal, batteries, &c), and organic refuse. The drop-off bins are housed within well designed closets for easy use with good instructions and green roofs. The municipal refuse collection company removes the refuse from bins within the closet. Organic refuse is collected in a series of 1 m3 boxes in the block. At any time, only one box is unlocked. When it is full, the next box is opened and the full box is locked. At the end of the year, all of the boxes are removed and composted to create fertilizer by the caretaker company hired for maintenance. It is a simple solution that works well except for the high level plastic bags used which pollute the refuse stream.
In 1992 the plan for the Kolding urban renewal project was presented as an integrated solution by one of the leading Danish urban renewal companies. The idea was to implement a renewal project which includes a set of measures to beyond the normal Danish standard of installing water-saving devices and energy-efficient electrical appliances.
The pyramid and surrounding infrastructure was built by the City of Kolding as a pilot project. Once finished, it was given to the inhabitants of the block as a gift. The organization of owners is responsible for billing for wastewater treatment. The monthly charge for wastewater with the Bioworks is actually less than the municipal waste water treatment plant. The regular maintenance for wastewater treatment is performed by a landscaping company who also looks after the green space within the block. In the case of damages to the system, such a broken pump or broken window, the organization of owners pays for replacement.
The residents continue to use the pyramid to purify their wastewater, but all other functions it was planned to serve has ceased. Of the 120 homes it serves, only 30 are occupied by their owners, and the rest are rented. Once a week, a staff member checks all of the gauges to make sure the system is working properly. Once a year, all of the pumps are maintained by a technical company. In the event of a problem, the landscaping company is alarmed and comes to fix it.
Operationally, the largest problem is odor, which is a serious nuisance to the inhabitants. The aeration pond is an open system, and continually smells like sewerage, the strength of which varies from day to day depending upon the weather. Regarding the reuse of rainwater, one difficulty has been slightly dirty water after a long period of no rain in which dust settles on the roofs. Many complaints have been filed after this first rain. The solution is further filtration of the rainwater before use, or education of the inhabitants that the water may be clouded. In the driest part of the year, the rainwater must be supplemented with drinking water.
The Bioworks has a strong spatial quality. It is a four-story glass pyramid injected into a city block with landscape architecture elements in its surroundings, notably a infiltration pond, community garden, and recreation area.
The Bioworks is an older pilot project at fifteen years of age. Since it was constructed several advances have been made, such as small-scale anaerobic digestion. It continues to perform its main function of water purification, however, it is very noticeable that the inhabitants have lost interest in the pyramid. Four levels in the pyramid were planned as greenhouse space for the inhabitants; now it is only partially used by one hobbyist gardener (at no cost), while most of the greenhouse beds sit empty. This can also be seen beside the pyramid, where a piece of land was set aside for urban agriculture and now sits unused. At the base of the pyramid, there are three water ponds in a cascade which hosted tilapia fish when it was constructed, but now only support algae. According to the caretaker, the problem is three-fold: firstly, the community has changed from owners to renters, and the renters have no long-term invested interest in utilizing the space provided; second, no professional cultivator can use the greenhouse because it is too small with too many stairs; third, the pyramid is a repetition of service, because almost every apartment is equipped with its own glass-enclosed patio in which small plants can also be grown with more convenience.
Alternatively, the pyramid could have been connected to a cafe which might be interested in using the glasshouse for cultivation of small foods for clients. This is not an option for Kolding, because the pyramid sits within the block with no street front and also no area that could be turned into a kitchen and dining room.