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Biological systems have been employed successfully for manv years in the treatment of pulp and paper mill waste water. Previously, not very much was known about enzymes and their possibilities in pulp and paper industry wastewater treatment. There is currently a lot of research activity in the enzymology of lignin degradation. Ligninase, cellulase, peroxidase, etc. are the most important enzymes, especially peroxidase, which is used for color removal in bleaching effluents. It is also possible to mix enzymes together with special microbes, which normally do not have high enzvme activity, and remove recalcitrant and harmless compounds from wastewater. The use of novel enzymes and rDNA technology in sludge and wastewater treatment will also be discussed.

Biodegradation in fixed film reactors of chloroorganic compounds in kraft bleaching effluent and in pesticides was studied. Specific biofilm reactors could be adapted for the mineralization of chloroform, chlorophenols, chlorocatechols, chloroguaiacols, chloroveratroles and chlorinated resin acids in bleaching effluent and for chlorophenols in spills of pesticides for blue stain and wood rot. Mineralization of chloroorganic compounds into inorganic chloride and carbon dioxide occurred in the solid phase of the reactor. The ability to degrade the chlorine compounds could be transferred from one reactor to another by transferring the liquid but no degradation occurred before addition of solids in the reactor. The degradation of pentachlorophenol was most active when softwood bark was used as the solid material It was less active on unglazed pottery, and inactive on glass (beads or fibre), cellulosic fibre, clay and ion exchange resin. The mineralization of the chloroorganics occuring in kraft bleaching effluent was less fastidious about the type of solid materials used. The biofilm grew equally well on softwood bark, ion exchange resin and various types of plastic and fiber.

Pure cultures of facultative anaerobic bacteria and yeasts were isolated from anaerobic reactors fed synthetic wastewater which contained eight different chlorophenolic compounds. The concentration of facultative anaerobic micro-organisms was followed in the reactor throughout the experimental period, during which the chlorophenol concentrations were increased and many of the chloronated phenols were removed nearly completely. The most common species were Klebsiella spp. and K. Pneumoniae. Some of the common colonies were tentatively identified as Pseudomonas-like organisms and Aeromonas hydrofila. Methanogenic bacteria in the reactor were mainly acetate users. When the total chlorophenol concentration in the feed was increased from zero to 2.4 or 5.3 mg/1, the concentration of Pseudomonas-like organisms increased, as did the concentration of yeasts. Pure and mixed cultures were tested for use of 2,4,6-trichlorophenol (246-TCP) as a sole carbon and energy source under anaerobic conditions. None of the isolates were able to degrade 246-TCP under anaerobic conditions in pure culture. However, mixed cultures containing only P. aeruginosa and K. oxytoca were able to degrade 246-TCP.

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