Drainage and Sanitation

In line with the goal of achieving environmentally friendly urban development, drainage and sanitation was included in the overall planning concept:

• In the context of a pilot project for creating a "wastewater-free housing estate", a urine separation system was installed in 88 dwelling units and in the elementary school. The system employs special toilets that are operated just like conventional toilets. The recovered urine is used as fertilizer for agricultural purposes. The solid wastes are composted.
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• The grey water, i.e. the water from showers, dishwashers and washing machines, is clarified in a constructed wetland on site and ultimately discharged into the nearest stream.
• A rainwater management system with vegetated swales, infiltration ditches und retention basins ensures that rainwater can seep away and evaporate on site.
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• Gravity sewer pipes have been constructed and connected with the existing sewers in the urban district of Pichling West.

In addition to the use of regenerative (solar) energy, the introduction of a closed loop system, which protects the environment to the greatest possible extent, increases the ecological value of the overall energy concept implemented in the solarCity.

Innovative Wastewater Concept for the solarCity

Linz AG developed a concept that provides new alternatives for disposing of wastewater.

This new wastewater concept was implemented as a pilot project in 88 dwelling units and in the elementary school. The persons in charge expect the pilot project to provide explicit findings that can be used in creating future-oriented wastewater systems, which are an important issue, particularly in conurbations. The results are being eagerly awaited by all concerned.

Recovering nutrients instead of flushing them away

The goal of the project is to return nutrients to the natural cycle by using them in agriculture. A precondition for doing so is the separate recovery and treatment of the various wastewater constituents (urine, black water and grey water). This is achieved by employing urine separation toilets in conjunction with two separate pipework systems, one for grey and black water and one for urine.

Fertilizer for agricultural purposes

Urine contains nutrients (nitrogen, phosphorous, potassium), which can be recovered and stored (by means of urine separation) and then used as liquid fertilizer for agricultural purposes. The black water (containing feces) and grey water (waste water from kitchens and bathrooms) are filtered in a vermicomposting tank where, after the addition of sufficient bulking material, the solids are pre-composted.

The rest is used for compost

The overflow from the vermicomposting tank is clarified in a constructed wetland, after which the clarified wastewater can be discharged into small receiving streams. After a year, post-composting is carried out at a compost site. Ultimately, the mature compost can be used in gardening and landscaping or as fertilizer for farming.

The Rainwater Concept in the solarCity

In planning the solarCity in Linz, an innovative approach was taken in many areas. In addition to architectural quality and a resident-friendly infrastructure, particular priority was given to the issues of energy efficiency and sustainability. Special emphasis was also given to the integration of sustainable rainwater management into the overall concept.
In line with this ambitious philosophy, a so-called modified rainwater management concept was developed for the solarCity, based on the following principles:

• Rainwater is dealt with as and where it occurs, in a surface-oriented, decentralized system that makes the natural rainwater cycle visible and comprehensible.
• The drainage, collection and disposal of rainwater is achieved mainly by means of gutters, retention hollows and vegetated swales.
• These are integrated into a coherent, interconnected system that uses the Aumühlbach stream as a receiving water body in the southern part of the district and the alluvial meadows as a recipient in the northern part.
• The aforementioned elements of rainwater management are an integral part of the planning of the open spaces.

Retention hollows and vegetated swales constitute an element of this concept. These are shallow grassy hollows which are integrated as harmoniously as possible into the open spaces and which, in the case of certain intensive rainfall scenarios which occur statistically every five years, retain water up to a maximum depth of 30 cm. This accumulated water drains away either by seeping into the vegetated surface or through a restricted drainage pipe. As a rule, the accumulation period is not longer than 12-16 hours and, as already mentioned, statistically this maximum only occurs about once every five years. The embankments of these hollows and swales are very shallow, not steeper than 1:2, and due to the maximum collection height of 30 cm, not too high. They are, moreover, overgrown with grass and easy to walk over even when wet.