Appropriate sanitation facilities are still a challenge in many parts of the world, particularly in developing countries. With regard to almost 950 million people defecating in the open, the question arises whether the existing treatment facilities are sufficient to provide for a healthy sanitation in the world. This paper mainly emphasizes on developing countries (particularly, India) where cost is generally a very important parameter of judgment for choosing the appropriate system. This makes decentralized treatment systems much more suitable for installation as they are easier to build and operate, both financially and technically. This paper includes basic differences and fundamental explanations about the processes involved in different decentralized treatment systems and their comparison on the basis of installation cost carried out by using a technology ranking method. It is concluded that waste stabilisation ponds would be most cost effective solution from capital investment point of view. However, Multi Criteria Analysis (MCA) should be carried out for appropriate technology selection in different scenarios on the basis of different criteria. New developments in sanitation technologies can play an important role in selecting appropriate sanitation technology for a particular scenario.