Black tank odor - switch to macerating toilet?

[Toolman]

Having trouble with these photos 

https://photos.app.goo.gl/MzkgE7teuZvVBF8CA

https://photos.app.goo.gl/9ZAi7JZ6pnhCJjTJA

I hope that you get the idea 

[Jcparmley]

Toolman do you have a pic of the air vent going to your engine air intake?  Not quite sure what you mean by a Venturi.  Thanks

The answer is very simple , I pump a small amount of compressed air from the bus into my tanks while driving
I also vent my tanks ( 40mm ) back to a venturi in the engine air intake, before the air cleaner.
I also have a small fish tank air pump that I can use if stopped for some time. the air is pumped in the bottom of the tanks and bubbles up through the contents = no smell   

[Toolman]

No photo, I would have to take the air intake apart. It is nothing more than a 1-1/2" pipe welded into the air intake. The pipe protrudes into the airstream alittle with the upstream side of the pipe maybe sticking out 1/4". the other side is level with the intake. Simple way to create a low pressure area = suction. Hope I make sense. It was already in the bus to draw air flow through the bathroom as has been talked about.