While arsenic is the largest contaminant, the other heavy metals, such as cadmium can cause problems in trace amounts. Those metals will contaminate the sediment, and every time the mud is stirred up, it will become available.
I’m not saying to expect a lot of one-eyed deer, but if I had a kid, or Mrs. VanShuyten was gravid, I’d be real cautious about drinking the water.
I’d think the heavy metals will reduce themselves rather quickly but you don’t want the drink the effluent just right now. This could have been corrected quickly.