J. Bio. Env. Sci.5(5), 75-81, November 2014
Suspended load concentration is a dominant factor on the health of rivers. Increase in suspended sediment load has many negative effects on the health of river. Identification of effective factors on fine particles sedimentation is a key aspect in sediment engineering. Comprehensive researches was not carried out on the effects of different factors in clay particle sedimentation in river flows and many researches has been carried out in salt waters or sea water. In present research, by a physical model with one sedimentation column, (1 m high and 25×25 cm2 square section) observation and measurement of the settling velocity of suspensions during the free and hindered settling stages is carried out and the effect of three main factors (initial solid concentration, temperature and salinity) is investigated. Based on the results, if we use auxiliary mechanisms for increasing of settling velocity, due to the impact of solid concentration (50%), we will need to enhance this mechanism in high initial solid concentration. The effect of salinity on sedimentation of fine sediment particles doesn’t have regular process. When the salinity increase in more than 4ppt, has limit effect on the settling velocity that the results of present research confirm it in 13%-20% initial solid concentration. Temperature has considerable effect on the settling velocity of fine particles. We can observe that with increase in temperature from 10 C to 45 C, critical sedimentation time decreases 49% approximately. So increase in temperature has positive effect on the settling velocity generally.
Chien N, Wan ZH. 1983. Mechanics of Sediment Movement, Science Press, Beijing, China (in Chinese).
Gailani J, Ziegler CK, Lick W. 1991. ‘Transport of suspended solids in the Lower Fox River’, J. Great Lakes Res., 17(4), 479–494.
Huang W. 1981. ‘Experimental study of settling properties of cohesive sediment in still water’, J. Sediment Res., No. 2, 30–41 (in Chinese).
Lick W, Lick J. 1988. ‘Aggregation and disaggregation of fine-grained lake sediments’, J. Great Lakes Res., 14(4), 514–523.
Li ZH, Nguyen KD, Brun-Cottan JC, Martin JM. 1994. ‘Numerical simulation of the turbidity maximum transport in the Gironde Estuary (France)’, Oceanologica Acta, 17(5), 479–500.
Mehta AJ. 1986. ‘Characterization of cohesive sediment properties and transport processes in estuaries’, Estuarine Cohesive Sediment Dynamics, A.J. Mehta (ed.), Springer-Verlag 290–325.
Newman ACD. 1987. The interaction of water with clay mineral surfaces: in Chemistry of Clay and Clay Minerals,A.C. D. Newman, ed., Mineralogical Society, London, 237-274
Owen MW. 1970. ‘A detailed study of the settling velocities of an estuary mud’, Report No. INT 78, Hydraulics Research Station, Wallingford, UK.
Shang JQ. 1997. ‘Zeta potential and electroosmotic permeability of clay soils’, Can. Geotech. J. 34, 627–631.
Thorn MFC. 1981. ‘Physical processes of siltation in tidal channels’, Proc. Hydraulic Modelling Applied to Maritime Eng. Problems, ICE, London, UK, 47–55.
Yue PJ. 1983. ‘Preliminary study of flocculation formed by cohesive sediment and its influence on rheologic properties of slurry’, J. Sediment Res., No. 1, 25–35 (in Chinese).