If the work upstream has ...
Published by Oswell Kapotsa, Regional Head - Northern Namibia at Heat Exchange Products
If the work upstream has caused upsets in your process then you have to find out exactly which water analysis parameters have changed i.e is it turbidity, pH, toc? Usually, if the PAC was working well before then it should still work, only now you have to compensate for the changes in the mentioned parameters by using a polyelectrolyte to deal with the high turbidity or adjusting the pH. If the organic content of the water has significantly increased, you might need to try Ferric Chloride as your primary coag. If these strategies do not work, then you have no other choice but to redo the process of finding a new coagulant altogether by doing new jar tests with many different reagents. Good luck.