Hard to say what that is - the fact the samples consistently look the same is meaningful - one key to idenitfying a parasite (if it is one), is finding eggs or "ova" - they can be tiny or not. anything floating that is oval or round worth getting - there should be lots of them.
If I took a guess, it looks like a Ascaris lumbricoides or large round worm - males are thinner than females which are pencil diameter thick - I think its too thin even for male, and it is really long for that... look up photos and see if similar - compare egg/ova pics to what you find.