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Title: Gravity thickening of biological sludges
Author: Lockyear, C. F.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1980
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A new laboratory method of predicting the thickening characteristics of compressible sludges is proposed. The method uses a low-speed centrifuge to simulate the compressive effect of different sludge blanket depths by applying different centrifugal accelerations. The test can be conducted in a few hours using less than a litre of sludge. The rate of thickening is observed with the aid of a stroboscope synchronised to the speed of the centrifuge. The results are analysed mathematically and compared with results from full-scale and laboratory-scale batch thickeners and from a pilot-scale continuous thickener, operated at various solids loadings and sludge blanket depths. The test was used to characterise rapidly a wide range of sewage and industrial sludges and mixtures of sludges. The application of this technique is also shown by studies of sludge compressibility, solids concentration gradients, and the effect of chemical coagulants on sludge thickening. The compressibility of various sludges determined using the centrifuge is compared to that obtained by filtration measurements. The effect of the compressibility of the sludge on the concentration gradient in the thickener is determined experimentally and the gradient compared to that obtained in the centrifuge tubes. The addition of a polyelectrolyte to a primary sewage sludge is shown to increase the rate of thickening up to some maximum, but to decrease the ultimate solids concentration with increasing dose.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available