Hydantoin Effects on Hypoclorite and Hypobromite Biocidal Efficacy in Alkaline Papermaking Applications, 1996 Papermakers Conference Proceedings

Hypochlorite is a well known, highly effective papermaking slimicide. Unfortunately, hypochlorite is also highly reactive towards furnish components decreasing efficacy and increasing total organic halogen (TOX) effluent concentrations. Non-biocidal, N-hydrogen hydantoins have been recently shown to increase hypochlorite biocidal efficacy and decrease TOX production in acidic furnishes. As alkaline furnishes and hypobromite applications are increasing in popularity, the effect of pH on hypochlorite:hydantoin systems and the performance of hypobromite:hydantoin systems were examined. Hypochlorite biocidal efficacy was dramatically enhanced by 5,5-dimethylhydantoin (DMH) under alkaline (pH = 7.8) conditions. Efficacy was increased by more than two-fold. Such enhancement was similar to that of previous acidic (pH=5.2) tests, demonstrating hydantoin applicability over a broad pH range. The hydantoin containing systems also demonstrated a rapid rate of kill providing efficacy at the shortest (5 min) contact time tested. In addition, residual hydantoin analyses showed quantitative hydantoin recovery, indicating the potential for a high degree of hydantoin recycle. In contrast to the hypochlorite results, hypobromite efficacy was not significantly enhanced by DMH. Hydantoim:hypochlorite systems provided the highest efficacy overall. cost performance analyses indicate hypochlorite:hydantoin systems to be significantly lower in cost than both hypochlorite and hypobromite systems when hydantoin recycle is considered.