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Slow sand filtration in remote communities in the Northern Territory

Purser, Megan (2016). Slow sand filtration in remote communities in the Northern Territory. Bachelor of Engineering Co-op (4th Year Project) Thesis, Charles Darwin University.

Document type: Thesis
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Author Purser, Megan
Title Slow sand filtration in remote communities in the Northern Territory
Institution Charles Darwin University
Publication Date 2016-10
Thesis Type Bachelor of Engineering Co-op (4th Year Project)
Supervisor Thennadil, Suresh
Fairfield, Charlie A.
Phasey, Jordan
Subjects ENGINEERING
0904 - Chemical Engineering
Abstract Yuelamu is a remote community located 270km north-west of Alice Springs that is serviced by Power and Water Corporation. The primary source of potable water is a dam located at the community. A surface water safety assessment conducted in 2015 indicated that the dam is a high contamination risk and the current water treatment regime does not meet health-based treatment targets recommended by the Water Services Association of Australia. Slow sand filtration has been identified as a potential option to provide an extra treatment barrier to address this shortfall. Slow sand filtration is a mechanical and biological process used to improve water quality. Power and Water Corporation were interested in the feasibility of slow sand filtration at Yuelamu and other remote communities in the Northern Territory.

A pilot slow sand filter was constructed at Yuelamu as a means to determine how appropriate this technology would be in Central Australian environmental conditions. A monitoring program was implemented to establish the efficacy of the filter at improving water quality. Operational parameters including intermittent operation, the effectiveness of harrowing as a cleaning method and cycle duration were assessed over a four month period.

Due to a blue-green algal bloom in the Yuelamu dam, the raw water quality entering the filter exceeded recommended limits in terms of true colour, algae and turbidity. This had a significant impact on both operational and water quality outcomes. The results suggest that the slow sand filter is effective at reducing E. coli, coliforms, cyanobacteria, intracellular cyanotoxin, and turbidity, but inferior when compared to the literature. Dissolved organic carbon, total plate count and chlorine demand analysis results indicate that effluent water quality was poorer. This suggests that the sand filter bed is promoting the growth of microorganisms.

Intermittent operation of the slow sand filter resulted in increased maintenance due to slime production in the inlet and outlet pipework. It also resulted in the filter environment becoming anaerobic. Due to the presence of high levels of algae, filter cycle times were shorter than the literature suggests. Harrowing was an effective method of cleaning to reestablish outlet flow from the filter. However, it did compromise the effectiveness of the filter indicating that a re-ripening period is necessary.
Keyword slow sand filtration
potable water treatment
microbial reduction
biological filtration


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Created: Mon, 16 Jan 2017, 10:44:41 CST by Jessie Ng