I am not familiar with SBR, but do kow a little about waste water plants. If you have a large swing in waste water composition, I recommend having a feed tank to your WWTP large enought to dampen the swings. Bugs can adapt to large loads, but don't like change.
Good luck.
I am not sure what your system looks like, but I have seen a vessel purge done with natural gas to a fuel or flare system, followed by nitrogen. This allows you to sweep the H2S/hydrocarbon to fuel/flare without blowing H2S all over the place (or putting excess nitrogen to fuel/flare).
I am...
I hate to start this thing going again, but if anybody is still out there- here I go. There has been lots of talk about residual elements in carbon steel used in HF service in the refining industry. Even when using carbon steel care should be taken to make sure you are using the right stuff...
As mentioned above, only special alloys should be used with HF. If you have questions about how to handle HF, don't do it. Somebody will get very hurt. Find an expert and listen to them. Harmful liquid, deadly vapor, don't mess around.