It is critical that chemical ...

It is critical that chemical oversimplification never be applied. Every system is unique. Systems may have what would appear to be the same issues. That does not mean they are the same. Many years ago this issue was driven home for me. There was a cooling system that had been treated extremely successfully for many years. A new unit was built along side that was an exact duplicate of the original. Within 2 weeks, the water in the new system was turbid. Within 6 weeks, the primary air aftercooler was experiencing heat transfer issues. The unit was taken down and the aftercooler was fouled. How could that be? The water was the same, controls were the same, the chemicals were the same? Flowrates the same, H/E design the same? Everything you could identify was the same. There was only one thing that was different.  The cooling tower sump on the new unit was 2x the old one. This would not seem to be as big a deal as it was. The solution was to partition the new basin. Problem went away.