Forms of Biocides

Biocide products, as sold by service companies, are generally available in both solid and liquid forms. Each form additionally offers various ready-to-use oxidizing and nonoxidizing chemistries. 

These different forms and chemistries are reviewed in this section, with practical comments and notes, where appropriate. 

Usually these products are oxidizers, and considerable success has been established over the years in small cooling systems, with mixed oxidizers of differing ratios, available as slow-release tablet (puck) and stick forms [such as l-bromo-3-chloro-5,5-dimethylhydantoin (BCDMH)]. These solid products are usually retained in a GRP (glass-reinforced plastic) or PVC (polyvinyl chloride) tank, often called a brominator.  

The brominator is installed permanently by the side of the cooling tower, and makeup water (or a sidestream of cooling water) passes through the tank, slowly dissolving the tablets and adding halogen to the water (see Section 6.2.7 on BCDMH for more details and recommendations). 

The concept of dispensing biocides or biostats in tablet form has recently been extended to the supply of certain nonoxidizers, such as 2,2-dibromo-3-nitrilopropionamide (DBNPA) (which has been widely available for many years as a liquid product and to a lesser extent as a powdered product). 

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