According to the IPC the vent should be tied into the building's venting system or terminate outdoor as the waste the pump receives is by code definition sewage ("Any liquid waste containing animal or vegetable matter in solution, including liquids containing chemicals in solution." - IPC) making this a sewage ejector which requires venting by section 916.5.1 of the IPC. I think the argument that the plumber could make is that because of the backcheck valve in the discharge line, no sewer gas could possibly make it back into the container so the only smell would come from anything actually in the container itself. The other thing that could be noted is the drain line on the outlet side does not comply with section 704.2 ("Change in size. The size of the drainage piping shall not be reduced in size in the direction of the flow" - IPC)
