Personally I'd go for manure proper for "letame" - the stuff peasants scatter on their sown fields - ad sewer for "liquame" - the mixed fluids that run through the sewer.

Manure is not, strictly speaking, slurry. rColin gave you an excellent suggestion.
The legalistic/academic/sporting "vs" looks very comical in this poohy-peey context but that's not your fault but your customer's. "and", as rColin puts it may work: need to see more text. If it's discoursive, my "as opposed" may fit less comically.