Cementing drain and return ?

Should I be cementing my sump plumbing into the threaded drain and return pipes, or should I be using a threaded attachment instead for each.I read that that cementing was the best option. I have enclosed a picture for a better understanding.

 

It looks like your bulkhead is a slip x slip not threaded so you would slip the inside standpipe or return inside the bulkhead and glue a piece of PVC pipe long enough it could be cut with a hacksaw in the future and still have enough sticking out to reglue.
Better yet go with TxT bulkheads and threaded male adapters then you can take things apart easily in the future as you will want to disassemble for cleaning once in awhile.

If what you picture is already glued it needs to be tossed and start over. Pipe must be inserted fully in the socket in order to seal and the pipe and fittings need to be primed before gluing.

Bulkheads are classified by their internal threads or slip(socket) not by the external threads which are solely for tightening up the jamb nut to hold it in place. The external threads are not normally a standard pipe thread and are not tapered so will not seal if you try to screw to the outside.

 

As I said on TRT, all fittings are seated as far as the would go and they are all primed and glued.

 

They are not seated all the way or the collar or raised portions on the reducer bushings would be touching. Fittings and pipe will always bottom out if they are cut squarely and prepared correctly.