I have had problems with odor coming out of my black tank vent on the roof of the camper. If there is no wind that day, or if the wind is just a little wrong, it can get very stinky. Late last season I started using the product listed below. It seems to be working so far. But, I have not tested it out for very long.
https://www.amazon.com/Walex-TOI-91799-Deodorizer/dp/B0006GF5SK/ref=sr_1_sc_3?ie=UTF8&qid=1479489993&sr=8-3-spell&keywords=rv+tank+treetmentI wonder if the Happy Camper stuff would help with odor as well as this seems to do ?