All of the technologies use solvent in treating the bitumen at one point of the process. So all of the tailings ponds contain solvents. In comparison with the naphthenic acid material, the solvents are readily biodegradable. So they pose a short-term environmental issue, but they don't have the kind of persistence in the environment that the naphthenic acid material has.
As for other chemicals that are added, some of the companies use sodium hydroxide or lye to adjust the pH to make the water less acidic, but that's a relatively benign additive. One company uses a citric acid, which is found in orange juice. So it's readily biodegradable.
So there are some additives used, but for the most part, they're less of a concern in terms of environmental impact than the acids that come out of the bitumen.