A fluidized layer of granular material used for the separation of particulate impurities in drinking water treatment
This paper deals with the application of a fluidized layer of granular material (FLGM) for the direct separation of destabilized impurities during drinking water treatment. Further, it investigates the effect of operation parameters (fluidized layer grain size, technological arrangement, velocity gradient, retention time, dosage of destabilisation reagent and temperature) on the aggregation and separation efficiency of the layer. The tests were carried out in a pilot plant scale. Aluminium sulphate was used as the destabilisation reagent. The highest separation efficiencies were achieved, when the particles entered the fluidized layer immediately after the dosing of the destabilisation reagent, when they had the lowest degree of aggregation. The separation efficiency (φ) also increased with increasing velocity gradient and the maximal value was reached at the velocity gradient of about 250 s-1. The most efficient separation of aluminium was achieved at 5 °C, but the effect of temperature on the efficiency of organic matter separation (φTOC) was not very significant. The maximal efficiency of separation on the layer grains reached the values φAl = 0.81 at the optimal dosage DAl = 1.55 mg L-1 and φTOC = 0.31 at the optimal dosage DAl = 2.36 mg L-1. The indisputable advantage of using FLGM for the separation of impurities is that they are intercepted on the layer grains in a form of solid, water-free shell (or coat) with the density of 2450 kg m-3, and there is no need to deal with the sludge dewatering.
AHSAN T., ALAERTS G.J., BUITEMAN J.P., 1996: Direct horizontal-flow roughing filtration. J. Water SRT - Aqua, 45, 5, 262-271.
BRATBY J., 2006: Coagulation and flocculation in water and Wastewater treatment. IWA Publishing, London.
COUFORT C., BOUYER D., LINE A., 2005: Flocculation related to local hydrodynamics in a Taylor-Couette reactor and in a jar. Chem. Engin. Sci., 60, 8-9, 2179-2192.
COUFORT C., LINE A., 2006: Hydrodynamic conditioning of aluminium-bentonite flocs. Water Sci. Technol. - Water Suppl., 6, 1, 11-19.
EDWARDS G.A., AMIRTHARAJAH A., 1985: Removing color caused by humic acids. J. AWWA, 77, 3, 50-57.
FRANCOIS R.J., VAN HAUTE A.A., 1985: Strength of aluminium hydroxide flocs. Water Res., 19, 10, 1249-1255.
GREGOR J.E., NOKES C.J., FENTON E., 1997: Optimizing natural organic matter removal from low turbidity waters by controlled pH adjustment of aluminium coagulation. Water Res., 31, 12, 2949-2958.
GREGORY J., DUAN J., 2001: Hydrolyzing metal salts as coagulants. Pure Appl. Chem., 73, 12, 2017-2026.
HEREIT F., MUTL S., VAGNER V., 1980: Formation of separable suspension and methods of its evaluation. J. Water SRT - Aqua, 29, 5, 95-99.
MONK R.D.G., TRUSSELL R.R., 1991: Design of mixers for water treatment plants: rapid mixing and flocculators. Mixing in coagulation and flocculation. AWWA Research Foundation, Denver, Colorado, USA.
MUTL S., KNESL B., POLASEK P., 1999: Application of a fluidized layer of granular material in the treatment of surface water. Part 1: Aggregation efficiency of the layer. J. Water SRT - Aqua, 48, 1, 24-30.
MUTL S., KNESL B., POLASEK P., 2000: Application of a fluidized layer of granular material in the treatment of surface water. Part 2: Separation efficiency of the layer. J. Water SRT - Aqua, 49, 4, 181-202.
MUTL S., POLASEK P., PIVOKONSKY M., KLOUCEK, O., 2006: The influence of G and T on the course of aggregation in treatment of medium polluted surface water. Water Sci. Technol. - Water Suppl., 6, 1, 39-48.
MUTL, S., POLASEK, P., 1993: Purification of water from impounding reservoir by a fluid layer of granular material - Plant design and performance results. Proc. Int. Conference WISA, Durban, South Africa.
O'MELIA C.R., BACKER W.C., AU K-K., 1999: Removal of humic substances by coagulation. Water Sci. Technol., 40, 9, 47-54.
PIVOKONSKY M., PIVOKONSKA L., TOMASKOVA H., 2008: Aggregation capability of a fluidised layer of granular material during treatment of water with high DOC and low alkalinity. Water Sci. Technol. - Water Suppl., 8, 1, 9-17.
PIVOKONSKY M., POLASEK P., PIVOKONSKA L., TOMASKOVA H., 2009: Optimized reaction conditions for removal of cellular organic matter of Microcystis aeruginosa during the destabilization and aggregation process using ferric sulfate in water purification. Water Env. Res., 81, 5, 514-522.
POLASEK P., 2007: Differentiation between different kinds of mixing in water purification: back to basics. Water SA, 33, 2, 249-251.
POLASEK P., MUTL S., 1995: Guidelines to coagulation and flocculation for surface waters. Volume 1: Design Principles for coagulation and flocculation systems. P. Polasek and Associates. Marshalltown, South Africa.
POLASEK P., MUTL S., 2005: Optimization of reaction conditions of particle aggregation in water purification: back to basics. Water SA, 31, 1, 61-72.
TAMBO N., MATSUI Y., 1989: Performance of fluidized pellet bed separator for high-concentration suspension removal. J. Water SRT - Aqua, 38, 4, 16-22.
TAMBO N., WANG X.C., 1993: Application of fluidized pellet bed technique in the treatment of highly colored and turbid water. J. Water SRT - Aqua, 42, 5, 301-309.
VIANA M., JOUANNIN P., PONTIER C., CHULIA D., 2002: About pycnometric density measurement. Talanta, 57, 3, 583-593.