Green chemistry (GC) is the key to sustainable development as it will lead to new solutions to existing problems. Moreover, it will present opportunities for new processes and products and at its heart is scientific and technological innovation. This paper aims to contribute to a better understanding of the new challenges that chemistry is facing. A particular emphasis is accorded to the need for the development of environmentally friendly technologies for water treatment where GC can be satisfied. Indeed, following the establishment of the 12 Principles of GC, there has been a steady growth in our understanding of what GC means. Furthermore, there are great perspectives relating to the greening of chemical water treatment, especially in terms of ferrate(VI) adding, as oxidant/disinfectant/coagulant in the same time, and microchannel reactors which would be considered as promising devices for water treatment due to their proved advantages. (C) 2011 Elsevier B.V. All rights reserved.