Hi,
It sounds like you must do original research for your project. As such no project we suggest will be acceptable, so let me address the process of getting into chemistry as a career.
Most of us start out by studying chemistry with no particular direction in mind, we just take chemistry courses or read books that survey chemistry. Sometime in our late teens we start to think seriously about what we want to do with our lives, and often settle on a direction. Picking this objective is the one of the most important decisions we will ever make. Most nascent chemists pick a problem they want to solve, usually by identifying a problem that is very important to the community in which they live. If they live in an area where water is very scarse or hard to attain, they might think the most useful thing they can do is to find a way to obtain large supplies of potable water more cheaply than the current method in their community. If a family member has died young of a disease or condition, they might want to find a cure for that disease or a way of preventing whatever caused the death of their relative. If there is not sufficient food in their community and people are starving, then they might decide to find a way to grow more food, make better use of the food they have(prevent decay or destruction of food by spoilage or vermin), make food production less expensive, or something similar, etc. In one case I know of, the person realized that ladies were having children too young and being trapped having to rear children full time trapping them in poverty by preventling them from learning skills that could enable them to earn a decent living - he addressed this issue by discovering a way to allow ladies to control when they got pregnant, and then built a very successful company (Syntex) to manufacture and distribute this medication to women worldwide. Chemists who are successful pick problems that they can solve, and problems that are very important to community in which they live.
The next step is to learn everything possible about the problem and all potential solutins that might work to solve the problem. If there is a good, effective solution known, then all you have to do is prove that it works well and is more cost effective/cheaper/better than the method in common use, and then convince your community to use the solution. If a known good solution can not be found, then you have to devise one- ie conduct research to find and develop s solution before introducing and selling your new solution to your community.
For someone just starting to practice chemistry, historically the entry path starts with a mentor or apprentniceship. This has been true for hundreds of years, and has been followed by almost all people who have become successful as chemists. The process works something like this: the student decides the general problem area he/she wants to work on, then searches out someone who is working on the same or similar problem, and convinces them to accept them as an apprentice or mentee. The contract is ideally something like this- the student agrees to provide the mentor free labor and their creativity to help solve the problem the mentor/professor/master want to solve. The master/mentor/professor provides the apprentice/student/mentee access to his knowledge about the problem, access to tools to study the problem, and access to his network of colleagues who know about or are interested in the problem. This apprentice relationship usually lasts until the problem is solved or student is able to be self sufficient or for a fixed period of time. (The master is sometimes called a mentor or thesis advisor or major professor - the mentee may be called a student, a graduate student, or a post doc.)
I apologise if this is all obvious to you- but I got well into college before it really became clear to me, and no one really ever explained it to me.
You appear to have decided the problem you want to solve is water purification. The next step is to survey the methods available for water purification and convince yourself that your idea will be better than the existing methods if it works, otherwise you will be wasting your time. In parallel with this process I highly recommentd that you find an appropriate mentor to help you with the project. (This has the potential advantages of access to expert advice, access to tools you need, introduction/recommendation to useful contacts, and possibly even some financial support.)
Science Buddies has some information of finding a mentor and executing an advanced science project:
https://www.sciencebuddies.org/science- ... ndex.shtml
If you are located in Indea you may wish to investigate the Indian Chemical Society:
http://indianchemsoc.org/aboutus.htm
You might be interested in this abstract on page 3 or this site:
http://www.indianchemsoc.org/journals/jan11.pdf
It describes the Arsenic in groundwater in areas of India and remedies for it.
Good luck,
Barrett L Tomlinson