A combined up-flow anaerobic sludge blanket and biofilter as an improved alternative on-site sanitation in urban Bhutan: lab-scale to pilot studies

Dorji, Ugyen

A combined up-flow anaerobic sludge blanket and biofilter as an improved alternative on-site sanitation in urban Bhutan: lab-scale to pilot studies

Dorji, Ugyen

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Publication Type:: Thesis
Issue Date:: 2020

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Field	Value	Language
dc.contributor.author	Dorji, Ugyen
dc.date.accessioned	2021-05-24T05:13:35Z
dc.date.available	2021-05-24T05:13:35Z
dc.date.issued	2020
dc.identifier.uri	http://hdl.handle.net/10453/149147
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	Providing public sewerage system for all emerging towns in Bhutan is a big challenge. This study observed about 80% of urban population in Bhutan depends on the on-site sanitation comprising septic tank and soak-pit. A proper soak-pit is essential for current on-site sanitation in disposing hazardous septic tank effluent through soil treatment. However, the survey showed about 40% of the existing urban on-site sanitation in Bhutan lacks soak-pit posing a significant risk to public health and environment from septic-tank effluent discharged into the environment. Most urban plots were found impractical for soak-pit installation due to small plots, high build-up areas and compacted soil fills. This study underscored the need of an alternative on-site sanitation that does not require soak-pit for final effluent disposal. Therefore in this study, a combined up-flow anaerobic sludge blanket (UASB) and anaerobic biofilter (ABF) system was explored as a complete on-site wastewater treatment system to provide improved alternative to the current on-site sanitation. UASB replaces septic tank for effective treatment of blackwater while watertight ABF replaces soak-pit. Shredded waste plastic bottles is used as ABF media for further treatment of UASB effluent and greywater combined to produce final effluent that can be safely discharged to the environment without the need of a soak-pit. Currently, greywater is discharged into the drains without treatment. The use of waste plastic bottles makes biofilter not only cheaper but helps solve mounting plastic waste problem in Bhutan. Both bench-scale studies using synthetic wastewater and 1000 L/day UASB-ABF pilot-scale demonstration in Bhutan using real wastewater from 2-3 households were conducted as part of the work. These studies have shown the new treatment system is effective compared to current on-site system producing final effluent lower than 125 mg/L COD, 30 mg/L BOD and 100 mg/L TSS that meets the effluent discharge standards of Bhutan. However, E.coli removal was five log units, which suggests that with process optimisation, E.coli removal can be further enhanced. Waste plastic bottle strips, charred bamboo beads & industrial slags were also observed to be an effective biofilter comparable to the commercial media. Economic assessment indicates the capital and maintenance cost of UASB-ABF wastewater treatment system is affordable as it is not significantly higher than the current on-site sanitation system. The new system is slightly more complex but it is also an opportunity to create new wastewater service industry that provides specialised contract services contributing to Bhutan’s economy.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/149147/1/02Whole.pdf
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	au.edu.uts.lib/ppc
dc.rights	info:eu-repo/semantics/openAccess
dc.title	A combined up-flow anaerobic sludge blanket and biofilter as an improved alternative on-site sanitation in urban Bhutan: lab-scale to pilot studies	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*

Abstract:

Providing public sewerage system for all emerging towns in Bhutan is a big challenge. This study observed about 80% of urban population in Bhutan depends on the on-site sanitation comprising septic tank and soak-pit. A proper soak-pit is essential for current on-site sanitation in disposing hazardous septic tank effluent through soil treatment. However, the survey showed about 40% of the existing urban on-site sanitation in Bhutan lacks soak-pit posing a significant risk to public health and environment from septic-tank effluent discharged into the environment. Most urban plots were found impractical for soak-pit installation due to small plots, high build-up areas and compacted soil fills. This study underscored the need of an alternative on-site sanitation that does not require soak-pit for final effluent disposal. Therefore in this study, a combined up-flow anaerobic sludge blanket (UASB) and anaerobic biofilter (ABF) system was explored as a complete on-site wastewater treatment system to provide improved alternative to the current on-site sanitation. UASB replaces septic tank for effective treatment of blackwater while watertight ABF replaces soak-pit. Shredded waste plastic bottles is used as ABF media for further treatment of UASB effluent and greywater combined to produce final effluent that can be safely discharged to the environment without the need of a soak-pit. Currently, greywater is discharged into the drains without treatment. The use of waste plastic bottles makes biofilter not only cheaper but helps solve mounting plastic waste problem in Bhutan. Both bench-scale studies using synthetic wastewater and 1000 L/day UASB-ABF pilot-scale demonstration in Bhutan using real wastewater from 2-3 households were conducted as part of the work. These studies have shown the new treatment system is effective compared to current on-site system producing final effluent lower than 125 mg/L COD, 30 mg/L BOD and 100 mg/L TSS that meets the effluent discharge standards of Bhutan. However, E.coli removal was five log units, which suggests that with process optimisation, E.coli removal can be further enhanced. Waste plastic bottle strips, charred bamboo beads & industrial slags were also observed to be an effective biofilter comparable to the commercial media. Economic assessment indicates the capital and maintenance cost of UASB-ABF wastewater treatment system is affordable as it is not significantly higher than the current on-site sanitation system. The new system is slightly more complex but it is also an opportunity to create new wastewater service industry that provides specialised contract services contributing to Bhutan’s economy.

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