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The impact of selected water and wastewater treatment process variables on sludge dewaterability

Fitria, D 2014, The impact of selected water and wastewater treatment process variables on sludge dewaterability , PhD thesis, The University of Salford.

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Abstract

The most significant operational cost in a treatment plant is related to the dewatering and disposal of sludge. Coagulation is the most common process in water and wastewater treatment plants and produces sludge as a by-product. The influence of different important coagulation factors has been investigated in this study to assess corresponding impacts on sludge dewaterability. The CST (Capillary Suction Time) apparatus was used as the main tool to measure sludge dewaterability, followed by the turbidimeter, the particle size analyzer, and the SRF (Specific Resistance to Filtration) as a comparison and also for verification. The CST results indicate that the magnetic stirrer produces the lowest CST values, while the other four shapes of mixers produced similar but higher trends. Rapid mixing velocity and rapid mixing time have varying degrees of influence on the CST value and hence on sludge dewaterability. Rapid mixing velocity seems to have a more significant impact on the CST value than rapid mixing time. The coagulants aluminium sulphate and ferric chloride have similar effects on CST values. The performance of aluminium sulphate and Moringa oleifera are affected by temperature, but the performance of coagulant ferric chloride was hardly impacted. Different synthetic water samples do not significantly affect the CST value. The turbidity result correlates well with the CST value. Observations using the particle size analyzer indicate that, in general, the floc size has a direct correlation with the CST value. The larger the floc size, the lower the CST value. Floc size distribution results show that synthetic raw water has a narrow particle size distribution; synthetic domestic wastewater produced a wider distribution than synthetic raw water. The comparison between the CST and SRF results indicates that the CST and SRF are well correlated if different methods (rapid mixing velocity and rapid mixing time) are used, but uncorrelated if different materials (mixers, coagulants, temperature and water samples) are used. Based on the results of this investigation, the working of the magnetic stirrer should be investigated further in order to implement this mixer in the treatment process. The magnetic stirrer does not only produce the lowest CST value but is also the only mixer that produces different CST values significantly. This is because it produces the optimum G value for sludge formation. The implementation of rapid mixing velocity is more important than rapid mixing time in the operation of a treatment plant. Due to its correlation with temperature, ferric chloride is the most appropriate coagulant among the three types of coagulants used in the treatment plant to reduce sludge dewaterability. Based on the results using different water samples, all of these factors can be used for both inorganic and organic water and wastewater to produce lower sludge dewaterability.

Item Type: Thesis (PhD)
Themes: Subjects outside of the University Themes
Schools: Schools > School of Computing, Science and Engineering
Schools > School of Computing, Science and Engineering > Salford Innovation Research Centre (SIRC)
Funders: Indonesian Ministry of Education (DIKTI)
Depositing User: Miss Dewi Fitria
Date Deposited: 11 Jul 2014 12:41
Last Modified: 30 Nov 2015 23:53
URI: http://usir.salford.ac.uk/id/eprint/31957

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