Can Flushing a Cigarette Butt Down the Toilet Damage a Septic System?

Thank you, everyone for responding! The LL did look at it and doesn't know what it is but wondered if it was minerals or something like that. I think the algae might be most accurate as it does look like it. He does pump out the system periodically (or according to the recommendations anyway). He is very careful not to use treatments in it. It is a mystery to him and me but if we find out for sure, I'll be sure to let you know.

Thanks for everyone's input! I appreciate it!

If you have gunky water coming into the toilet bowl when you flush, it is not coming from the septic system, but from your toilet tank. This has nothing to do with the flushing of the cigarette butt. Take the lid off of your toilet tank, and have a look at what is in there. Perhaps you have growth of algae going on, sometimes that is black and gunky. If you do, you can shut off the water, clean this out (it wouldn't be harmful, just slimy), and give it a shot of bleach when you turn the water back on and the tank fills up.

I can't imagine one single cigarette butt causing the problem! When was the last time your landlord had the septic tank pumped? It's more than likely the cigarette butt incident is simply a coincidence and the system hasn't been pumped in the past few years!

One other thing. Does your landlord regularly use treatments, such as Rid X, that break down the sewage waste? Both the pumping and the treatments are the landlords responsibility for the upkeep of 'their' system.

Check out this website, I think it will be helpful for you.
http://extension.umd.edu/environment/water/files/septic.html