You might try changing your titles and see if they get more traffic. For instance the septic tank article would probably get a lot more if it was "How to empty septic tank less". Leave the details, such as the use of micro-organisms, for the readers to pick up. Use a title that is more likely to be googled.
I have several articles that are rated high on google, usually just the ones with very simple titles, such as "Skinny Dog Breeds", "Dog Breeds Who Dont Bark, Much". I have an article titled "How to compost dog waste, correctly" and it had almost no traffic. I changed it to "How to compost dog poop", which is googled a lot more frequently, but I still have little traffic, so there are no guarantees out there!
When you change the title, resubmit the URL to webmaster tools. It will speed things up a little.