Cyanuric acid is used in conjunction with hypochlorite for maintaining disinfection against protozoa, bacteria and viruses in swimming pools and hot tubs. Upon repeated addition, hypochlorite is bound up in an inactive form and disinfection is lost. A biocatalytic process has been developed to remove cyanuric acid to acceptable levels and restore water disinfection. The biocatalyst is cyanuric acid hydrolase (CAH), that opens the stable triazinone ring with subsequent decarboxylation making the reaction irreversible. CAH enzymes represent a rare protein fold with three domains that fold around the three-fold symmetric substrate. CAH enzymes are found in less than 1% of bacteria, with a geospatial survey identifying them largely in agricultural fields. A preferred CAH for swimming pool water treatment was identified by searching a public and private database of &gt; 500,000 bacterial genomes. The CAH from <i>Pseudolabrys</i> sp. Root1462 had the necessary kinetic properties, thermal stability and storage stability for commercial applications. A pool treatment protocol was developed and used the following steps sequentially: (1) remove residual pool hypochlorite using sodium sulfite, (2) treat the pool water with CAH, and (3) add hypochlorite at the desired endpoint. The hypochlorite step inactivated the remaining enzyme activity and oxidized the biuret produced by the enzymatic reaction to form primarily dinitrogen and carbon dioxide gases. The level of biocatalyst required is sufficiently low to make this a viable method for treating home, municipal and commercial pools.

Commerical-Scale Biocatalytic Treatment of Pool and Spa Waters to Remove Cyanuric Acid

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ACS Fall 2022

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