What is the alternate to SA account in SQL Server? My client is currently using SQL Server for their app. At this time they are using SA account everywhere. For security reasons we need to disable the SA account. The solution I've is create another power user (not admin), like standard user and root user. The development only needs access for CRUD operations. So, what should be the rights/roles/privileges for this new account? We need to replicate the same model to the internet server where only read rights are required (from viewer's end). How do I go about it?

Two different versions, 2008 R2 and 2012.
On your development server, you can grant the standard users the db_datawriter and db_datareader roles. You probably want to grant the db_owner role to the power user. As these are database level roles, you have to repeat this for each of your databases. Regarding the web server, you should create a limited user that only has been granted the db_datareader role.

As the sa login is hardcoded to be a member of the sysadmin server, you can't limit the permission of this account. The best way to migrate is to replace all the connection string you can find and then finally disable the sa account.