Since you are the second floor of the ground floor, I suggest you consider this way, -1F commercial if there is drainage, such as supermarkets, fresh food, catering kitchens, etc., consider the structure of the lowering of the plate to do the ditch, pooled to -2F drainage, -2F can be made a room as a grease trap room. -1F of the parking lot ground drainage, you can consider the floor drain collection, to -2F discharge, discharge into the -2F catchment wells, -1F of the bathroom drains in the top of the -2F, directly to the -2F discharge, you can make a room to place the sewage catchment wells, remember to close the lid, placed in the odor overflow. -2F floor drainage can be two practices, according to my experience, because you since it is -2F, certainly the structure of the base plate thickness is relatively thick, you can consider the use of floor drains to take over the introduction of the way to the catchment wells (need to pay attention to the drain buried in the base plate between the upper reinforcement and lower reinforcement, according to the norms of the slope), or the use of the floor trench can also be.

Generally like you say this kind of project is not simple, you ask this question again, no harm, just feel that you are not in full control of this project, it is best to have seniors can always consult, help you pre-determined. Instead of asking casually online, so as not to cause rework and bring trouble to other professions.