"Should filters be used on cooling water systems?" is a question I am often asked. So what do I say? Well, it depends on a number of considerations, but my first response is absolutely an unqualified "Yes." Filters are a cost-effective investment. Filters remove suspended solids from the cooling water and thus reduce many problems. So, what are these considerations?

"Do all closed chilled water systems need water treatment?" is a question I have been asked numerous times. Why is it asked? Well, I know of persons who have been in charge of closed chilled water systems that do not use any water treatment chemicals whatsoever -- and operate trouble-free.

An oxidizing microbiocide is as any chemical that is an oxidizing agent. They are chemicals that kill and destroy not only the microorganism but also the nutrients found in cooling water. Their action is essentially "wet oxidation" or "burning" under water. No microbiological organism is immune to this action -- provided that the oxidizing biocide can reach the microorganisms.

Cooling water microbiological control is important all year long -- and even more important during the warm days of summer. This is not only due to warmer water temperatures but also due to more nutrients and microbiological organisms entering the cooling tower system from the air.

In addition to deposit-forming microorganisms and iron-depositing, sulfate-reducing and nitrifying bacteria, there are two other mechanisms that cause MIC: denitrifying bacteria and acid producers.

What is MIC? It stands for microbiologically influenced corrosion -- yes, corrosion in water systems due to microbiological organisms. These microbes do not "eat" metals such as mild steel, stainless steel, copper alloys or galvanized steels. Rather, they produce byproducts that are corrosive to these metals.

Cooling tower water systems are composed of three major sections: cooling tower, chiller or heat exchangers, and piping. Each section must be considered when designing a cooling tower water system. Often, initial capital cost of equipment is a strong driving force. Little, if any, water treatment costs are incorporated in the design and equipment purchase decision.

Part 1 identified the steps in setting up a corrosion monitoring program, including the use of corrosion coupons. Two additional corrosion-monitoring techniques are available: electric resistance (ER) and linear polarization resistance (LPR). In Part 2, I'll look at these methods in detail.

These are some of the common questions end users and owners often ask. However, often they are asked after equipment replacement has occurred or about to be due to corrosion. Here, I hope to provide you some guidelines and helpful advice for corrosion testing of the components in your cooling water system so that they will last longer.