Sewage is what we flush away and prefer not to see, so it is read as unwanted emotions or memories resurfacing. Wading through it stands for dealing with something unpleasant that can no longer be ignored.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.