Monitoring of active ingredients in cooling water programs has, in recent years, been supplanted by the use of tracers, as some active components are not readily testable at the field level. This paper will look at the criteria that should be used to determine valid product testing methods and alternatives that exist commercially.
Monitoring of actives, in water treatment programs has been a constant, regardless of the type of program or the system being treated. In the area of cooling water, early programs based on chromate could be monitored by doing little more than looking at the color of the water. With the movement to more environmentally friendly programs and the need for more stringent control, monitoring became more critical. Concurrent with this, as the cost of labor has increased and the relative cost for automation has declined, the use of on-line systems has become more prevalent.
BACKGROUND
In discussing monitoring and the trends that have taken place over the past two decades, the obvious question is what are the objectives that need to be satisfied? Cooling water technology supplied by the major water treatment companies has evolved to the point that with reasonable product selection and application skill, acceptable performance results will ensue. So what are the objectives, if the programs are fundamentally sound?
The reason for testing for actives, in cooling water treatment programs, falls in to one (or more) of the following categories:
1) Indirect Performance Measurement
2) Ensuring Regulatory Compliance
3) Safety
4) Program Economics
The primary driving force over the past 5 ? 10 years has been the last parameter, as companies have struggled to find ways to lower their operating costs.
Indirect Performance Measurement
As stated earlier, standard cooling water programs such as those based on inorganic phosphate, zinc or organic programs have proven track records and a well established application history. Given that they work and the application criteria are well established, there are only three questions that need to be asked, to ensure that the results will match expectations:
1) is the program suited to the application
2) is the treatment/product level appropriate
3) is the level of product maintained
The first question is addressed by the training provided from the water treatment supplier and the assumption that a suitable treatment chemistry is selected. The second point relates to the matter of economics and the degree to which a buffer was incorporated into the specified feedrates. The crucial question is the third one; will the plant be able to maintain control of the product level within the specified control range and how best to achieve this.
The underlying assumption is that if the measured concentration is acceptable, the performance will be directly related to it, i.e. as the level of product falls, the scaling or corrosion rate will rise. Everything else being equal, the success of the program will be directly related to the ability to control the product level in the cooling water.
In addition, some programs which are inherently fouling (e.g. inorganic phosphate containing) can be the direct cause of scaling if they are chronically overfed. Hence large variations in the residual can lead to both scaling or corrosion problems. This does not mean that control of the cooling water chemistry does not matter but rather, automated systems to ensure parameters such as pH and conductivity are well
established.
Regulatory Compliance
Current cooling water programs are environmentally friendly but, at the same time regulatory r
