Water, treatment cooling

Organophosphonates are similar to polyphosphates in chelation properties, but they are stable to hydrolysis and replace the phosphates where persistence in aqueous solution is necessary. They are used as scale and corrosion inhibitors (52) where they function via the threshold effect, a mechanism requiring far less than the stoichiometric amounts for chelation of the detrimental ions present. Threshold inhibition in cooling water treatment is the largest market for organophosphonates, but there is a wide variety of other uses (50). 

Silicates at about 20-40 p.p.m. are also used in cooling-water treatment although the build-up of protection can be slow. At higher temperatures calcium silicate may be deposited from hard waters. 

NOTE In cooling water treatment, although temperatures tend to be lower, antifoams and defoamers must be able to withstand strongly oxidizing conditions. 

Dispersible silicone emulsions are generally preferred for aqueous systems, whereas silicone fluids and compounds are preferred for non-aqueous systems. Silicones are widely employed in cooling water treatment programs, less so in boiler plants because of higher operating costs than available alternatives, but also because of sometimes questionable emulsion stability at higher temperatures. 

As with my first book, which covered cooling water treatment, this book also started life after rereading the (still largely relevant) books written by the late James W. McCoy, who was a supervisor of refinery services at Standard Oil Company of California. This time my primary source of inspiration was The Chemical Treatment of Boiler Water, which was first published by Chemical Publishing Company of New York in 1981. 

Toxic pollutants found in the wastewater streams are normally related to solvents and solvent impurities, product additives, and cooling water treatment chemicals. Table 7 presents a listing of the potential wastewater sources and the associated contaminants for this industry. 

Wang, L.K. Recent Development in Cooling Water Treatment with Ozone Lenox Institute of Water Technology Lenox, MA, 1988 Technical Report No. LIR/03-88/285, 237 p., March. 

W. L. Marshall, Cooling water treatment in power plants. Industrial Water Engineering February-March, 38-42 (1972). 

While minimizing blowdown volumes can be quite effective in reducing waste, removing the hazardous metals component of the waste stream can have a more dramatic effect on reducing the impact of the blowdown on the environment. Chromate based corrosion inhibitors have historically been the mainstay of cooling water treatment systems. But in recent years, some plants have elected to use nonchromate inhibitors in order to reduce the potential environmental problems associated with chromates. Types of nonchromate inhibitors that have proved useful and that have in some situations performed as well as chromates include (Roti 1985) ... 

All cooling water treatment programs, whether designed in-house or via a water treatment service company, continue to focus on the minimization of hard water crystalline scales and sludges in the system as a major criteria for success. Program techniques employed are either pretreatment processes, such as lime-soda softening or ion exchange, the use of sulfuric acid or polymer-based chemicals that operate in an alkaline environment, or combinations of some or all of these processes. 

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