4.6 V8 engine knocks after water pump replacement

[GRMont]

On a Lucerne CXL 4.6 V8, after getting the water pump replaced, the engine has a bad knock at low RPM. At highway speed, the noise goes away. Possible tensioner pulley, air in system? It didn't get overheated. Its odd that it started immediately after getting a new water pump put on it.

 

[2007LucerneCXL]

First step may be to take it back to the shop as there would be no way to know what the knock is over the forum. Lots of possibilities which you can see in the diagrams.