Your choice of system would depend on the end performance of the protective coating required.
Polyurea’s are commonly used in waste water applications due to their superior Hydrogen Sulphide (H2S) resistance.
Fire Retardant Coatings
Era Polymers offer one off the shelf Fire Retardant grade, Eraspray ESU500D FR. The addition of fire retardants can be made to all Eraspray systems.