Reference
A. Harrison - Presented at PAPTAC - June 2000
Abstract
BCDMH, Bromo chloro dimethylhydantoin, is a new oxidizing biocide registered for use in the Canadian Pulp and Paper Industry. BCDMH is an organic, bromine releasing biocide. It is a solid material which is safer to handle than the traditional oxidizing biocides - chlorine and sodium hypochlorite. BCDMH dissolves in water and rapidly hydrolyses to the active hypobromous and hypochlorous species. Hypochlorous acid in turn converts bromide back to hypobromous ion. BCDMH is a broad spectrum and fast-acting biocide which is effective over the pH range found in paper mill systems. BCMH has advantages over non-oxidizing biocides in alkaline waters high in organics and nitrogen compounds. Evidence of the safety of application is that BCDMH can be used in swimming pools and has NSF approval as treatment for potable water. The Swedish National Chemical Inspectorate (1994) has approved BCDMH as one of only 11 biocide actives approved for the pulp and paper industry.
A case study is presented to demonstrate the use of BCDMH in the Canadian paper industry. The study provides details about an application in a tissue mill using 100% recycled fibre furnish. The mill experienced unscheduled shut-downs for cleaning slime deposits. These deposits broke free from time to time from the slime accumulation on the machine frame and in the headbox and caused sheet breaks. A slime control programme was instituted based on DBNPA and BCDMH to replace the existing biocide programme which used a blend of quat chloride and sulfone. The mill saw benefits of reduced down time, fewer wet-end breaks and increased production. Paper quality improved because the hole count in the sheet decreased nearly to zero. Monitoring methods for the oxidizing biocide programme are reviewed.
Conclusion
Process B2015 G has been shown to be a fast acting, cost effective biocide in this tissue mill. As an oxidising biocide, BCDMH is a broad spectrum active and has reduced the contamination caused by bacteriological growth on the paper machine. Because it is a solid material, Process B 2015 G is safer to handle. Because it is a strong oxidizing agent BCDMH degrades rapidly and the degradation products are inert. For this reason BCDMH can be considered to be an environmentally safe product.
While BCDMH may not be the ideal biocide it is recommended as a cost effective biocide which overcomes many of the deficiencies of the non-oxidizing product currently used in the pulp and paper industry.