Can a person hold both roles; project management and business development at a same time in an organization?

Absolutly, if you choose the right person capable to do that.
It requires different focus - one is definite, project related - with clearly set targets, phases, etc...
The other one is indefinite - and more creative...
So it depends on the personality, but its possible.

i believe a good project manager cannot successfully perform the post of  a successfull business development.

 

inorder to be a successfull project manager you need descipline and to follow a structured path already set prior to project launch.you can deviate  but to some degree.

as for business development you must be a free spirited,creative,spontanious,flexible,....person to bring new improvements and adjustments to existing process,not following a pre defined structured path.

 

having a person with these two destinct qualities or skills is not easy.

Yes that is possible.....suppose some person is handling business development and new business model and its implementation comes under his role.
So in that case he / she has to develop the new business model and pilot testing at5-6 locations.
During that time he has to handle the Project Management also for creation of pilot locations.
But the project management of a large project along with the business development is little difficult as both the activities require huge amount of efforts and time.

Yes , and it is very normal specially in small and medium companies.
Business development and strategy are inline and Normally strategy comes before business development.
And formulating strategy have heavily involvement of the PMO specially from senior project managers.
But surely it is two hates on head and require large capacity and expertise .

A business development manager is a permanent post for the organization (as long as it is required). A project manager's role is limited to the time of the project he is managing.

A business development manager may manage project(s) as well. I belive that his holds true for any other managers as well.

Practically, 

I don't think so 

those two positions have a different scope

Yes, business development mainly requires developing or exploiting the organisation to perform new tasks and to align with customer requirements, which will sometimes initiate projects that would be serving this requirement, and in meduim level and some large companies, the business development manager can take up the project management, as (s)he would know best the needs, and would be abe to understand the required outcomes, and work to shape the project to serve those outcomes.

Project Manager has a key role to add more revenue to the organisation kitty.
To some extent having business development capabilities will be of immense use to make the role more effective.
The business developer with the analytical preparation of potential projects opportunities as well as the subsequent support and monitoring of its implementation.
Both in the development phase and the implementation phase, the business developer collaborates and integrates the knowledge and feedback from the organization’s specialist functions, for example, R&D, production, finance, etc.
to assure that the organization is capable of implementing the project opportunity successfully.
The business developers' tools to address the business development tasks are the business model answering "how do we make money" and its analytical backup and roadmap for implementation, the business plan.

there is a difference in the meaning of theoritical Project Manager and practical Project Manager. If you would look definition or JDs of the theoritical Project Manager then your answer would be YES, for this people need to understand that what a Business Development Manager does. Does the way BDM performs his works falls withing the defintion of Project? Once you will evaluate this you can have your answer