On-Line Measurement and Control of Bacteria Producing Nuisance Odors in Closed Paper Mill Water Systems, 1995 Pulping Conference Proceedings

K. R. Gurijala*

Betz PaperChem, Inc.

P. P. Chebi

Betz PaperChem, Inc.

Closed-circuit water systems of paper mills often include sites that serve as an optimum environment for nuisance microorganisms that produce volatile fatty acids (VFAs), namely acetate, propionate, and butyrate. The offensive odor of VFAs may result in a finished product that is unacceptable to customers and consumers. The accumulation of VFAs in the process streams also cause odors in the mill neighborhood. Therefore, an instrument was developed to monitor and control anaerobic bacterial activity in paper mill water systems to overcome odor problems caused by VFA-producing bacteria in process streams. The novel instrument that was developed is based on an instrument system which is interfaced with an on-line monitor that measures a specific by-product of anaerobic microbial activity. The instrument is monitored and controlled through proprietary software. On the basis of the anaerobic microbial activity that is measured by the on-line monitor, the instrument controls the addition of a biocide or a non-biocidal control agent to a previously chosen feed point in the mill water system. The addition of the bioactive agent continues until the measure of anaerobic activity is reduced to a pre-specified value. The equipment has been tested in paper mills containing closed-circuit water systems with a measurable odor problem. The instrument system effectively controlled VFA production in the process streams and the finished product. For example, in one trial, a 30 to 40% reduction in the VFA concentration in the finished product was achieved using 6 to 12% less biocide as compared to control achieved without the novel monitor.