Macerator is basically a positive displacement pump. It acts like vacuum cleaner. When you operate it, it sucks mostly all liquid in your plumbing system including the seal water in your p-trap in your sink and shower stall.
So,you are left with a clear "tunnel" to the CG sewer system. When you operate your macerator don't leave it running too long. . .just enough so you drain whatever is in the black or gray tank. After you're done with your
hygiene business for the night, pour some water in each of your sink/s and shower stall drains to achieve the seal.
Better still,don't use the macerator when you are ready to retire for the night.
Have a good night's sleep and sweet dreams.