Acting on behalf of the German Ministry for Economic Cooperation and Development (BMZ), GTZ is implementing projects to improve sanitation services in more than 25 countries. Its work involves providing organisational and technical advice to institutions and service providers, developing sustainable sanitation strategies and raising awareness among decision-makers and the general public. The aim is to work with the partners to change structures and processes within the country in order to bring about sustainable improvements in living conditions. A key factor of success is to focus on demand and on local needs when disseminating sustainable sanitation solutions. In order to be sustainable, sanitation systems must not only protect human health, be economically affordable, socially acceptable and technically and institutionally appropriate; they should also protect the environment and natural resources. In addition, ecological sanitation (ecosan) emphasises the safe reuse of wastewater and the use of the nutrients and organic matter contained in treated excreta in agriculture.