If there is no municpal sewer system availabe, there should be a septic system to take the waste. Usually a system includes a tank where any solids will sink to the bottom and the effluent (liquid) will drain off the top and into an absorption system. Some places will have a seepage bed which is maybe 500 - 1000 sq. ft. of gravel about 12" thick with perforated pipe running through it and covered with dirt. The effluent will drian out into the gravel bed and down into the ground. Some places use french drains which are basically a 2' or 3' wide trench with perforated pipe running through it and it is covered with gravel as well. I have also seen systems have an open pond in rocky areas where there is little soil. It evaporates and seeps slowly away.
There should not be sewage visible on top of the ground. If you are seeing something like this, you might want to call the local health department since this could be a health hazard. They will be able to tell you just what is required in your area.