Problem 10.4: A closed chilled water loop shows brown turbid

From Chapter 10 Problem Set. Level 1: Conceptual Mastery.

Question

A closed chilled water loop shows brown, turbid water at 45 NTU despite having been in operation for two years. Is this a suspended solids problem or something else? What would you investigate first?

Answer

Show answer

In a closed system that has been operating for two years, 45 NTU is almost certainly a corrosion problem, not an external solids problem. Closed systems are not exposed to atmospheric dust loading. The brown, turbid water is likely iron oxide from active corrosion of carbon steel piping. Investigate first: (a) check the corrosion inhibitor residual - is the treatment program being fed consistently? (b) filter a sample and examine the particulate - brown/red suggests iron oxide, black suggests magnetite or SRB activity, green suggests copper corrosion products. (c) check whether the system was properly flushed after construction - construction debris from two years ago can continue circulating indefinitely.