Foam in outdoor in-ground water feature with waterfall

Question
We just recently rebuilt the above-referenced water feature as we had a leak and was losing water.  Now we have heavy foam building up in the standing water at the base of the waterfall.  We put in a new liner and used some of the old liner to help redirect the water.  We removed the new filter pads and cleaned them to see if that would help but it did not.  Any suggestions to what we may have done wrong.

Thank you.

Answer
Sorry for delay.
But it a problem I have encountered once.
But by sealing the patch through which water from sewer was getting in. Also we could find the leaking sewage but it was a rare occurance of 2 things going wrong simultaneously. Otherwise washing of filter pads take care of things.