Selenium not freeing up memory even after calling close/quit
Are you trying to say that your drivers are what's filling up your memory? How are you closing them? If you're extracting your data, do you still have references to some collection that's storing them in memory?   
You mentioned that you were already running out of memory when you closed the driver instance at the end of scraping, which makes it seem like you're keeping extra references.
So I've been working on scraper that goes on 10k+pages and scrapes data from it.
The issue is that over time, memory consumption raises drastically. So to overcome this - instead of closing driver instance only at the end of scrape - the scraper is updated so that it closes the instance after every page is loaded and data extracted.
But ram memory still gets populated for some reason.
I tried using PhantomJS but it doesn't load data properly for some reason.
I also tried with the initial version of the scraper to limit cache in Firefox to 100mb, but that also did not work.
Note: I run tests with both chromedriver and firefox, and unfortunately I can't use libraries such as requests, mechanize, etc... instead of selenium.
Any help is appreciated since I've been trying to figure this out for a week now. Thanks.