Ben Aim, R, Liu, MG & Vigneswaran, S 1993, 'Recent Development of Membrane Processes for Water and Waste Water Treatment', Water Science and Technology, vol. 27, no. 10, pp. 141-149.
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Membranes are presently used at industrial scale for water and waste water treatment, but still for limited production. More knowledge of hydrodynamic phenomena has recently resulted in significant technical improvements (backflush, unsteady flow). However an experimental study performed at lab scale in a rotating membrane device has shown the complexity of the relationship between operating conditions, rejection and filtrate flux. The need for bettering the quality of the water (low turbidity) and waster water (disinfection) may be in favour of the development of membrane processes if efficient models allowing simultaneous optimization of quality and productivity are made available (as was done years ago for deep bed filtration).
Chiemchaisri, C, Yamamoto, K & Vigneswaran, S 1993, 'Household Membrane Bioreactor in Domestic Wastewater Treatment', Water Science and Technology, vol. 27, no. 1, pp. 171-178.
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The activated sludge process coupled with hollow fiber membrane for solid-liquid separation was applied to treat low strength domestic wastewater.
Pilot-scale experimental unit used in this study consisted of 2 modules of 0.03 μm pore size with 9 m2 surface area each, immersed in the reactor which has a maximum working volume of 1.5 m3. Even when sewage was fed at varying rates following its diurnal flow variation to the bioreactor, good stability of the process was achieved which was shown by the consistency in treated water quality. The effluent turbidity and COD were well within the limits (less than 0.5 NTU and 3-5 mg/L). The transmembrane pressure drop was less than 20 cm Hg even after 2 months of operation. Application of jet aeration could be used to prolong the operational life of the membrane in the bioreactor. This system is an ideal one to be used as household wastewater treatment system.
Dharmappa, HB, Verink, J, Fujiwara, O & Vigneswaran, S 1993, 'Optimal design of a flocculator', Water Research, vol. 27, no. 3, pp. 513-519.
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An approach is presented for the least cost design of a flocculator with respect to flocculation time and velocity gradient, in order to obtain a desired effluent condition, which is measured using the negative slope of power law distribution function (β). The model proposed is a non-linear programming problem involving a non-linear constraint, which in turn comprises a verified simulation model. The case study demonstrates the existence of a relationship between design criterion and design parameters. It also shows that the optimal solution is sensitive to influent particle size distribution (PSD) and particle contact efficiency (α).
Waite, TD, Amal, R, Ngo, H & Vigneswaran, S 1993, 'Effects of Adsorbed Organic Matter on Size, Structure and Filterability of Iron Oxyhydroxide Flocs', Water Science and Technology, vol. 27, no. 11, pp. 133-142.
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In this study, the effects of adsorbed fulvic acid, a naturallyoccurringorganic acid, on the aggregation and filtration of hematite particles are investigated. The study of aggregate structure shows that the fractal dimensions of hematite aggregates which are partially coated with fulvic acid molecules are higher than those obtained with no adsorbed fulvic acid. The high fractal dimensions are due to restructuring within the aggregates, which only occurred at low coverage by the organic acid. In the filtration experiments, high clean filter efficiency was obtained for particles with the net charge opposite to the filter media. During ripening period, however, the particle sizesplayed a more important role than the surface chargesParticles of a micron size seemed to have less capture efficiency during this period, since they are controlled neither by diffusion nor interception.
Zhou, JL & Banks, CJ 1993, 'Mechanism of humic acid colour removal from natural waters by fungal biomass biosorption', Chemosphere, vol. 27, no. 4, pp. 607-620.
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