Aluminum sulfate is a chemical conditioning agent in the water and wastewater treatment industry. If the aluminum sulfate does not contain any objectional materials, it may be possible to recycle the aluminum sulfate at a wastewater treatment plant. For example, aluminum sulfate is used for phosphorus material and is quite expensive.
Not familiar with incineration of aluminum sulfate. Since it is an inorganic material, I don't see any benefit to incineration.