Graduation date: 1994

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Note:

No description available.

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.

No description available.

The extracellular polymers produced by bacteria play an important role in bacterial aggregation or bacterial flocculation in secondary waste treatment. The mechanisms responsible for this floc formation are thought to be polymer induced adsorption and interparticle bridging among bacterial cells or between bacterial cells and inorganic colloids. The efficiency of the processes following flocculation in the treatment line such as sedimentation, sludge thickening, and sludge dewatering depends on the extent of this bacterial flocculation. In this research, sludge samples from under various substrate conditions were examined for type, molecular weight, physical characteristics„ and quantity of extracellular polymers so that the general characteristics of the various polymers could be established. An attempt was made to determine if a relationship exists between the state of bacterial aggregation and the polymer characteristics. This research also investigated the sludge physical properties. The effect of various parameters such as pH, divalent cation (mixture and concentration), and mixing (period and intensity) on dewatering properties were studied. A major goal of this study was to develop a flocculation model for activated sludge. This model could be used to determine if plants can increase the efficiency of waste treatment and sludge thickening and sludge dewatering processes. / Ph. D.

This study investigated the influence of nitrogen and sludge age change in reactor performance and biopolymer production in activated sludge systems. The qualitative and quantitative analyses of the naturally occurring biopolymers were performed and the results were correlated to sludge a settling characteristic and effluent quality. In order to obtain the sludge samples for the analyses, two completely mixed, continuous flow activated sludge systems were maintained during this research. Raw wastewater from the Celanese Fiber Plant located at Narrows, Virginia was utilized as the influent. Nitrogen was added in the feed solution as ammonium sulfate. The sludge age was changed from ten to five days for both systems. Biopolymers were extracted from the sludge floc matrix using pH-adjustment technique followed by centrifugation. The total biopolymer contents were analyzed for protein and carbohydrate concentrations. High molecular weight biopolymers were also analyzed following gel filtration. The sludge settling characteristics were measured in terms of Sludge Volume Index and effluent quality in terms of effluent turbidity. The results indicated that the relationship between total biopolymer concentrations and sludge settling characteristics is culture specific. No consistent relationship was observed between total biopolymer concentrations and effluent turbidity and/or SVI. Additional nitrogen in a reactor system promoted production of high protein content biopolymers. However, no significant improvement in effluent quality of the reactor was noticed by the additional nitrogen. Deficiency of nitrogen in a reactor system promoted the production of high carbohydrate content biopolymers. The high concentration of carbohydrate biopolymers seemed to correspond directly to the high effluent turbidity. / M.S.

The purpose of this investigation was to continue the color reduction study of alum treatment of caustic wash from chlorine bleached kraft pulp, to determine if a double tray Dorr thickener could be used to settle the coagulated waste, and to determine if a centrifugal separator could be used to dewater the sludge from the Dorr underflow. Approximately 5000 gallons of caustic wash from chlorine bleached kraft pulp was used for each phase of this investigation. The raw waste feed flow rate was varied from 1750 pounds per hour to 2499 Pounds per hour. The alum slurry flow rate was varied from 39 Pounds per hour to 60 pounds per hour. The hydrochloric acid flow rate remained constant at approximately five pounds per hour. The raw waste was acidified with 38 percent hydrochloric acid to a pH of 6.0, and treated with alum sulfate slurry to coagulate the solids in the waste. The coagulated solids were concentrated in a double tray Dorr thickener. The percent of insoluble solids in the Dorr underflow varied from 0.65 to 1.35. The concentrated solids were fed to a Merco centrifugal separator where the insoluble solids were concentrated in approximately equal proportions in the Merco overflow and underflow. / Master of Science

CNPq / No meio da ampla biodiversidade da flora brasileira, a ora-pro-nobis (Pereskia aculeata Miller) desperta especial interesse, pela alta quantidade de mucilagem em suas folhas. Plantas mucilaginosas são estudadas há algum tempo no processo de floculação/coagulação em tratamentos de água, com a intenção de, reduzir ou até mesmo suceder a utilização do sulfato de alumínio. A mucilagem é um biopolímero com grande capacidade de formar gel, soluções viscosas e estabilizar sistemas de emulsão. O presente trabalho teve como finalidade, avaliar o rendimento da mucilagem em processos de extração, caracterizar a mucilagem não clarificada, e clarificada e aplicar o biopolímero clarificado da P. aculeata, no processo de coagulação/floculação. Para tal as folhas foram secas em estufa até peso constante, foi feita a extração da mucilagem em solução aquosa por duas metodologias diferentes avaliando assim o rendimento, caracterização da morfologia por microscopia eletrônica de varredura (MEV) e difratometria de raio X (DRX), composição estrutural por infravermelho com transformada de Fourier (FT-IR), determinação do pH potencial de carga zero e do comportamento térmico por análise termogravimétrica (TG/DSC). Para a avaliação de coagulação e floculação, o biopolímero foi avaliado em água do Rio Pato Branco por ensaios em Jar Test avaliando a eficiência da remoção de turbidez, remoção de substâncias húmicas, e aromáticas. A extração da mucilagem foi avaliada no rendimento da produção, em que a extração a 95 ºC (30 min) apresentou rendimento três vezes maior que a extração a 60 ºC (6 horas). A caracterização morfológica exibiu uma estrutura amorfa, esponjosa e com adesão de partículas menores à superfície das partículas maiores, indicando um material higroscópico que pode ser usado como coagulante, sendo semelhante a outras mucilagens pesquisadas, em aspectos de grupos funcionais e de comportamento térmico. A P. aculeata se confirmou como auxiliar no processo de coagulação/floculação em relação aos parâmetros e faixas estudadas, sendo mais eficaz em conjunto com o sulfato de alumínio. Como é uma planta de fácil cultivo, atóxica e com custo relativamente baixo para a extração do seu biopolímero é uma alternativa promissora no tratamento de água e efluentes diminuindo a utilização do sulfato de alumínio no processo de floculação/coagulação. / In the midst of the wide biodiversity of Brazilian flora, the ora-pro-nobis (Pereskia aculeata Miller) arouses special interest because of the high amount of mucilage in its leaves. Mucilage plants have been studied for some time in the flocculation / coagulation process in water treatments, with the intention of reducing or even succeeding the use of aluminum sulphate. Mucilage is a biopolymer with great gelforming, viscous solutions and stabilizing emulsion systems. The purpose of this study was to evaluate the yield of the mucilage in extraction processes, to characterize the clarified and clarified mucilage and to apply the clarified biopolymer of P. aculeata in the coagulation / flocculation process. For this, the leaves were oven dried to constant weight, the mucilage was extracted in aqueous solution by two different methodologies, evaluating the yield, characterization of the morphology by scanning electron microscopy (SEM) and X-ray diffractometry (XRD) (FT-IR), determination of potential zero charge pH and thermal behavior by thermogravimetric analysis (TG / DSC). For the evaluation of coagulation and flocculation, the biopolymer was evaluated in water of the Pato Branco River by tests in Jar Test evaluating the efficiency of the removal of turbidity, removal of humic and aromatic substances. The extraction of the mucilage was evaluated in the yield of the production, in which the extraction at 95 ºC (30 min) yielded a three times higher yield than the extraction at 60 ºC (6 hours). The morphological characterization showed an amorphous structure, spongy and with adhesion of smaller particles to the surface of larger particles, indicating a hygroscopic material that can be used as a coagulant, being similar to other mucilages studied, in aspects of functional groups and thermal behavior. P. aculeata was confirmed as an aid in the coagulation / flocculation process in relation to the parameters and ranges studied, being more effective in conjunction with aluminum sulphate. As it is an easy-to-grow, non-toxic plant with relatively low cost for the extraction of its biopolymer, it is a promising alternative in the treatment of water and effluents by reducing the use of aluminum sulphate in the flocculation / coagulation process.