DHARMAPPA, H, VERINK, J, FUJIWARA, O & VIGNESWARAN, S 1992, 'Optimization of granular bed filtration treating polydispersed suspension', Water Research, vol. 26, no. 10, pp. 1307-1318.
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The need for economic optimization of a filter unit leading to its least cost design with respect to filtration velocity, run time, depth and medium size has long been identified but there are no algorithms towards this end. In this study, an algorithm incorporating a NLP (non-linear programming) software (NPSOLâSystem Optimization Laboratory, Stanford University, Calif.) and response surface methodology (RSM) is presented for optimal design and operation of a filter unit. Also, the simulation model included in the optimization takes into account the polydispersity of the influent. The optimization results obtained using laboratory data have shown that the filter design and operating parameters are highly dependent on the particle size distribution (PSD) of the influent. The cost of the filter unit with influent having the same total particles mass concentration and turbidity but with greater fraction of fine particles was about 46% higher. This demonstrates the importance of incorporating PSD instead of suspended solids (SS), turbidity units (TU) or volume average diameter in the design and operation of filter units. The proposed approach, however, is applicable only for single medium filters. Further research is warranted to extend it to dual and tri media filters.
Dharmappa, HB, Verink, J, Ben Aim, R, Yamamoto, K & Vigneswaran, S 1992, 'A comprehensive model for cross-flow filtration incorporating polydispersity of the influent', Journal of Membrane Science, vol. 65, no. 1-2, pp. 173-185.
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A semi-empirical model is presented for the prediction of foulant deposit thickness and concentration, and thereby, predicting the permeate flux in cross-flow microfiltration and ultrafiltration. The scope of the model is limited to colloidal suspensions (i.e. non-diffusive solutes) and its hallmark is its applicability to polydispersed influents. The theoretical model was verified with experimental observations and found to yield a fairly good agreement with an error less than 62% of the average flux over 100 min of filtration. However, evaluation of model coefficients a and b is necessary through laboratory studies. The model was successfully used to predict the effect of particle size distribution (PSD) on permeate flux. The simulation results corroborate the contention that the long-term flux decline is due to the reduction is foulant deposit permeability via infiltration of fines into the cake, thereby demonstrating the importance of influent particle size distribution (PSD) on foulant deposit permeability. The proposed model is a first step towards the modeling of polydispersed influents. As such there is a lot of scope for further refinements which is briefly discussed.
RALPH, PJ, BURCHETT, MD & PULKOWNIK, A 1992, 'DISTRIBUTION OF EXTRACTABLE CARBOHYDRATE RESERVES WITHIN THE RHIZOME OF THE SEAGRASS POSIDONIA-AUSTRALIS HOOK F', AQUATIC BOTANY, vol. 42, no. 4, pp. 385-392.
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Rhizomes of Posidonia australis Hook. f., collected from Botany Bay on the eastern coast of Australia, were analysed for extractable carbohydrates. The concentration of extractable carbohydrate in the stelar tissue of the rhizome was significantly higher
Zhou, JL 1992, 'Biosorption and desorption of humic acid by microbial biomass', Chemosphere, vol. 24, no. 11, pp. 1573-1589.
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Zhou, JL & Banks, CJ 1992, 'Humic acid removal from water by biosorptton', Environmental Technology, vol. 13, no. 8, pp. 727-737.
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