sledneck, I have dealt with a landfill LS before. This one handled leachate as well as domestic...roughly 50/50 flow from each source. Of course that station had serious corrosion issues, and a similar buildup of "unknown" materials, besides the obvious grease, that would line the walls, rails, floats, and anything else in contact with the water. But the station worked...albeit one that was high maintenance. The fact that a good amount of flow to the station was domestic did help dilute the leachate (ha....dilution with sewage was a good thing).
Do you have any ability to dilute the leachate in the station? domestic force mains nearby? a groundwater or stormwater source? Anything?
How much leachate per day is going to this station?
Also, are you sure you are getting 2 feet per second velocities in the FM?
I would also suggest keeping in mind that a pigging station or a pressure cleanout might help. This would allow the Utility to either 1) flush the line periodically or 2) send a "pig" through to clear any obstructions.