DETERMINATION OF MICROORGANISMS IN PAPER MACHINE WHITE WATER SYSTEM AND KILLING EFFECT OF

Abstract

Microbial problems in paper mills have significantly increased after closing up white water system to reduce fresh water consumption. Environmental constrains also have contributed to the need of reducing the amount of effluents. The recirculation of white water has created serious slime problems because of the growths of. microbes in the system. Increased recycling increases the amount of nutrient present in solids or dissolved form. It is quite obvious that due to recycling the concentration of nutrients considerably increases. Besides the microbial activity itself produces organic acids, vitamins, enzymes etc. to the systems. It is note worthy that also chemicals (viz, additives utilized in the production process) in themselves represents an ideal nutrient source (starch) or contain as impurities quite a lot of nutrients for microbes (Kaolin). Filler suspensions and additives used can contain considerably amount of phosphorus and Nitrogen, which along with the carbon source, is the principle nutrients for most microbes. The aim of this study was to access the microorganism in the white water systems of Star Paper Mill using cellulosic raw materials Viz., Popular deltoids, Eucalyptus Tereticornis and Bamboos aurandacea and manufacturing writing and printing and wrapping and packaging papers. In order to improve product quality and to explore the possibilities of reuse of recycled water different biocides were tested to examine their killing effect on different microorganisms. The stock preparation sections of paper machines 1-4 contain different composition of various nonfibrous additives. Therefore, the population of different types of bacteria may vary due to variation is composition of substrant types of bacterial like sulphate reducing bacteria, Iron bacterial, Pseudomonas, yeast and mould in each stock preparation sections. Keeping in view problems like production loss, inferior quality due to slime and minimum profit level various biocides were analyzed us laboratory to study the killing efficiency of different types of bacterial finally, a plant trail was conducted with high spectrum biocides. The process water of paper 'machine 1,2,3, & 4 contains total bacterial colony count 4.20 x 106. 7.12 x iø, 3.84 x 106 and 3.31 x 106 cfu/ml respectively. The yeast and mould in the process water of paper machine 1,2,3, & 4 are 49, 42, 44 and 46 cfu/ml respectively. The bacterial colony count of pseudomonas in the process water of paper machines 1,2,3, & 4 with a dilution of 10-' are 36, 32, 29 and 30 cfulml respectively. The bacterial colony count of iron bacteria in the process water of paper machines 1,2,3, & 4 are 45, 42, 39 and 36 cfu/ml respectively. The no. of sulphate reducing bacteria in the process water of paper machines 1,2,3, & 4 are 65, 62, 58 and 55 cfu/ml respectively. These values indicate that these bacteria not only fail to assure product and consumers safety but cause production loss also. In order to eradicate these problems the killing efficiencies of three different biocides i.e. 2,2 dibromo-3 nitrilopropionamide (A), alkali dimethyl benzyl ammonium chloride (B),and alkali dimethyl ammonium chloride (C) were tested. The biocide 2.2 — dibromo-3- nitrilopropionamide (A) is wide spectrum for all types of bacteria and fungi and killing efficiency is about 100% in most of the cases.