Sustainable water and waste management in urban areas

Sewerage system and centralised aerobic wastewater treatment plants (WTP) should not be considered as the only possible solution for sanitation. Systems with source control can avoid many problems of the end-of-pipe technology by respecting different qualities of wastewater and by treating them appropriately for reuse.

Different qualities of waste and wastewater in human settlements and appropriate treatment technologies can be: 1. low diluted faeces with/without urine and bio waste (composter or anaerobic digester), 2. grey ·water/aerobic biofilm plant, 3. storm water (usage and infiltration) and 4. non-biodegradable waste (reuse as raw material).

In order to perform resource management, the material originating from agriculture should be returned to the soil as fertiliser. Of similar importance is the organic material. This helps maintaining or building up humus and creates a sink for carbon when the C-content in the soil is increased. Energy will be saved, too: energy-intensive aerobic treatment with nitrification is obsolete as well as the production of the respective amount of replaced artificial fertiliser.

A pilot project for a new settlement for about 300 inhabitants in Lübeck, Germany, shall demonstrate the feasibility of a new integrated system with vacuum toilets and pipes for the collection of black water. This will be mixed with shredded bio waste and fed to a semicentralised biogas plant that produces liquid fertiliser without dewatering.

Grey water will be treated in decentralised biofilm systems. Storm water is collected, retained and infiltrated in a trench system. This way the expensive centralised sewerage system can be avoided for this settlement.