Comparison of two biocides - Carbamate and glutaraldehyde - In the controlof fouling in pulp and paper industry

Formation of fouling deposits is a serious problem facing paper mills. Desp ite the search for alternative methods, chemical biocides still represent t he chief countermeasure to control microbial growth and general fouling bui d-up in pulp and paper mills. The purpose of this work was to determine the effect of two biocides (carbamate and glutaraldehyde) on both planktonic c ells and fouling layers of a paper machine system. A flow system was used f or the study of fouling accumulation in an industrial white water circuit. Both biocides proved to be more effective in reducing the microbial loading of the white water circuit than the deposit accumulated on the stainless s teel surfaces. Carbamate, in contrast to glutaraldehyde, had the ability of promoting cell agglomeration since the microbial loading decreased much mo re when the white water, treated with carbamate, was filtered through a fil ter-linen. The retention of suspended cells in the cellulose fibres acquire s major importance since it is obtained by using an already existing physic al process (filtration), which strongly enhances the overall microbial redu ction obtained with the addition of the carbamate, without increasing the e conomic costs. These results also suggest that the use of conventional rete ntion agents in pulp and paper processes can be efficient in controlling un wanted microbial effects.