Treatment of Cooling Water
Many cooling systems use water as cooling medium. They are found in public buildings, industrial production systems or power plants. Almost every cooling system using water is degraded by deposition, corrosion and microbiological fouling. This book identi
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1 Water Analysis
The most important criterion of choice, when searching for an appropriate treatment, is the composition of the water available. Moreover, the analysis of treated water allows monitoring good functioning of the treatment applied. The purpose of the cooling water monitoring is to avoid the accidents described in the second part of the book, by maintaining the concentrations of dissolved salts, phosphates, silica, etc. within the limits required for good protection. The type and frequency of the analyses to be carried out vary depending on operating conditions and the observed incidents of functioning. In particular, in the case of large cooling installations, frequent analyses are not necessary, given the mass inertia related to the considerable volume of basins, in which concentrations change very slowly. In general, daily measurement of the calcium hardness, of the concentrations of chlorides, dispersing agents and corrosion inhibitors, as well as that of pH are sufficient. Bacteria counts must be performed every week. The choice concerning analyses and thier frequency should be made in collaboration with the water specialist, which will take into account the specificity of each system. Methods of the Legionella concentration analysis must be chosen in accordance with the relevant legislation in force, concerning the respect of standards imposed. The frequency of the analyses will depend on the level of Legionella concentration measured. The analyses should be carried out according to the method NFT 90-431. Within the framework of the Legionella risk management, the relevant analyses can be performed by using the PCR (polymerase chain reaction) method. Many analyses can be performed on site by relatively unqualified personnel using simple methods. There exist special analysis kits for water treatments, including the material and reagents required for the main analyses (titrimetry and colorimetry). It is nevertheless advisable to carry out periodic verification of the validity of results obtained using routine on site determinations, by qualified personnel in the laboratory. Moreover, some analyses are possible only in laboratory conditions.
Water Analysis
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A certain number of factors affect the precision and the validity of the results: — Reagents: they must always be prepared in a well equipped laboratory by qualified personnel. Their reactivity must always be verified and they must not be used after their expiration date. — Sampling procedure: it is important that the sample be representative of the water to be analyzed. Therefore, sampling points must be chosen. The recipient should be rinsed several times with the water to be analyzed before filling it with the sample. When a sample is taken from a valve or a faucet, the water should run several minutes before collecting the sample. Only clear samples are analyzed. It is advised to identify by a panel the place of sample chosen. — Temperature: certain measurements, such as those of pH and conductivity, are temperature sensitive. Ambien
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