The influence of nitrogen (N) and phosphorus (P) limitation on pulp and paper mill activated sludge (AS) floc properties was studied using a bioreactor fed with synthetic Kraft mill effluent. The bioreactor and synthetic effluent were designed and shown to perform like the real mill system providing the AS, establishing the in vivo relevance of the results. Limitation of either N or P produced inadequate effluent biotreatment, shown by poor BOD5 and suspended solids removal, and by decreased biomass health, performance, and floc settling. Greatly enhanced poly-beta-hydroxybutyrate (PHB) (but not carbohydrate or extracellular polymeric substances [EPS]) synthesis was the common response of the floc microbial community to N limitation over many days. In contrast, P-limitation increased total carbohydrate and EPS, but not PHB. / N limitation, but not P limitation, caused the net floc surface charge to be much more negative, while P-limitation, but not N-limitation, increased the floc bound water content and surface hydrophobicity. Thus, in real pulp and paper mill AS systems, careful manipulation of N or P additions may be useful to optimize the key process of charged polymer-assisted AS dewatering.

A method for the separation and detection of standard resin acids (RAs), commonly found in pulp mill effluent and known to bioaccumulate in fish bile, was optimized using cyclodextrin modified electrokinetic capillary electrophoresis (CD-EKC) with ultra violet (UV) and laser induced fluorescence (LIF) detection. Optimal separation conditions were found with RA standards using UV detection at 214 nm, with a 72 mM sodium borate buffer pH 9.25, containing 35 mM beta-cyclodextrin sulfobutyl ether (SPCD), 15 mM of methyl-beta-cyclodextrin (MECD) and a 37 cm capillary with an internal diameter of 50pm. This resulted in a 12-min separation and the identification of 9 peaks, with a LOD of 10 ppm. To enable increased sensitivity, RAs were derivatized using the fluorescent label 4-BrMMc. A method for extracting resin acids from spiked fish bile and pulp mill effluent was developed, the extracted samples were derivatized, separated and identified using CD-EKC with LIF detection. The method of extraction and derivatization using CD-EKC was applied to biological samples of contaminated effluent and fish bile. (Abstract shortened by UMI.)

This research followed acetate carbon (C) uptake, metabolism, and fate through a typical modern Kraft pulp and paper mill AS system. Freshly collected mill biomass (AS floc suspensions) was placed under conditions representing four key phases of AS biotreatment: (1) initial acetate uptake by aerated starved AS; (2) ongoing acetate uptake; (3) aerobic metabolism of acetate-loaded AS in acetate-stripped effluent; and (4) anaerobic, settled biomass metabolism. Conditions mimicked the mill system as closely as possible. Acetate carbon uptake kinetics and conversion to CO2, growth products, PHB, and secreted metabolites in each of the four phases were measured. The role of PHB synthesis in the initial stripping of acetate from mill effluent and the PHB production potential of this mill AS were also investigated. / Results showed that acetate was rapidly taken up by high-affinity systems in the AS. During the initial exposure of mill-starved AS, acetate greatly stimulated AS-O2 uptake, and was quickly converted to PHB and CO 2. Upon depletion of available effluent acetate, as occurs in the downstream sections of the aeration tank, O2-uptake rates decreased and the acetate-C stored in AS-PHB was slowly released as CO2, and partly used for growth. Under secondary clarifier-like anaerobic conditions, the AS released virtually no CO2. However, substantial amounts of PHB were used for growth under anaerobic conditions and a small proportion of the original acetate C exited the cells as organic acids.

Thesis submitted in fulfilment of Master's Degree in Technology: Biotechnology, Durban Institute of Technology, 2004. / M

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Master of Science