ABSTRACT
Reducing the use of the mains storm drains and the sewers by providing on-site systems to clean and drain or reuse rain-, grey- and blackwater can help to reduce the occurrence of sewage and stormwater pollution incidents; it can reduce the planned discharge of partially treated sewage effluent or polluted stormwater into watercourses; it can reduce the energy required to transfer and treat the waste water; and can contribute to replenishing groundwater sources. Of the three main approaches to reduce the use of mains drains, the simplest, when considering the technical and legal complexities, is to minimise stormwater run-off. On-site disposal of greywater also requires only limited expert support, while the treatment of blackwater on site is the most technically and legally demanding intervention. Sustainable Urban Drainage (SUD) initiatives
In Atlanta 20 per cent of the trees were removed for development, which resulted in increased stormwater of 150 million cubic metres. To build sufficient containment for this amount of water would have cost $2 billion. The alternative to replant trees not only was far cheaper, but also enhanced the local environment.
(Wilson 2002)Berlin has spent DM30 million over 12 years to replace concrete urban surfaces with planted surfaces to increase the natural water absorbance ability.
(Beatley 2000)