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Strength properties of composite clay balls containing additives from industry wastes as new filter media in water treatment


Type

Article

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Authors

Rajapakse, JP 
Gallage, C 
Dareeju, B 

Abstract

Pebble matrix filtration (PMF) is a water treatment technology that can remove suspended solids in highly turbid surface water during heavy storms. PMF typically uses sand and natural pebbles as filter media. Hand-made clay pebbles (balls) can be used as alternatives to natural pebbles in PMF treatment plants, where natural pebbles are not readily available. Since the high turbidity is a seasonal problem that occurs during heavy rains, the use of newly developed composite clay balls instead of pure clay balls have the advantage of removing other pollutants such as natural organic matter (NOM) during other times. Only the strength properties of composite clay balls are described here as the pollutant removal is beyond the scope of this paper. These new composite clay balls must be able to withstand dead and live loads under dry and saturated conditions in a filter assembly. Absence of a standard ball preparation process and expected strength properties of composite clay balls were the main reasons behind the present study. Five different raw materials from industry wastes: Red Mud (RM), Water Treatment Alum Sludge (S), Shredded Paper (SP), Saw Dust (SD), and Sugar Mulch (SM) were added to common clay brick mix (BM) in different proportions. A comprehensive experimental program was performed to evaluate influence burning temperature on crushing strength of composite hand-made clay balls, using uniaxial compression test to establish the best material combination on the basis of strength properties for designing sustainable filter media for water treatment plants. Performance at both construction and operating stages were considered by analyzing both strength properties under fully dry conditions and strength degradation after saturation in a water bath. Approximately 50 mm diameter composite clay balls fired at 800 0C provided sufficient strength for water treatment applications at both construction and operational stages due to their higher strength at dry conditions, and no strength degradation at soaked conditions. The use of water treatment sludge as an additive produced the lowest strength of composite clay balls, with a failure load of 1.4 kN. However, this value is much higher than the effective load on each clay ball of 0.04 kN in a typical filter assembly (safety factor of 35), therefore, can still be used as a suitable filter material for enhanced pollutant removal.

Description

Keywords

pebble matrix filtration, composite clay balls, material combinations, uniaxial compression test

Journal Title

Geomechanics and Engineering

Conference Name

Journal ISSN

2005-307X
2092-6219

Volume Title

Publisher

Techno-Press
Sponsorship
Authors wish to thank Queensland Alumina Limited (QAL) and Seqwater for supplying Red Mud and water treatment sludge for the experiments. The support of PGH Bricks and Pavers for firing composite clay balls in their factory is greatly acknowledged. Also, the support of technical and professional staff of the geotechnical laboratory at Queensland University of Technology during testing is highly appreciated.