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INTRODUCTION
About half of the world population currently lives in rural areas. In the EU, almost 30% of the overall population of the former CEE (Central and Eastern European) countries (42 million people) lives in settlements with less than 2,000 inhabitants, while the percentage is less than 20% in the western part. Many other areas of the world show a preponderantly rural character, although this tendency is slowly decreasing, due to the ongoing urbanization phenomenon. A large part of this population is still waiting for proper sanitation systems, or is aiming to improve the efficiency of existing ones and scale-up environmental protection and resources recovery. In most cases, centralized treatment systems for rural communities or peri-urban areas in low income countries would result in long-term debt burdens for the population (Parkinson & Tayler 2003), therefore system decentralization appears as a logical solution to tackle the problem, as these facilities can usually be built to fulfil current needs and be expanded as need arise. Even in developed countries, cities are gradually losing their character of densely concentrated settlements and are gradually sprawling to the countryside: the urban area of Paris now counts over 11 million inhabitants (up from about 4.5 millions in the early 1900's) and extends well beyond the original urban administrative boundaries (over 17,000 km2 versus the Ville de Paris’s initial 2,850 km2). In areas where construction of a sewage collection system is not considered economically viable, decentralization is becoming quite popular: as an example, 25% of the population in the US is already served by small, decentralised wastewater treatment plants (WWTPs) (UNEP 2002).
Sustainable decentralized sanitation focuses on on-site treatment and on recycling of resources contained in domestic wastewater, in primis, water itself. Other resources that can be readily recycled are: bio-energy (from transformation of organic material), and nutrients (mainly nitrogen and phosphorus). Decentralisation could therefore contribute to the continuing progress and completion of the Millennium Development Goals, promoting environmental sustainability and reversing loss of environmental resources. This tendency will be more relevant in the next future, thanks to new global pressures towards water management paradigms change, from waste-oriented approach to resource-recovery and water reuse ones. Such a move to decentralized water management even in developed countries’ urban areas, could be essential in...