Leanyer Sanderson Waste Stabilisation Pond Microbiology

  • Alea Marie Rose

Student thesis: Doctor of Philosophy (PhD) - CDU


The Leanyer Sanderson Wastewater Stabilisation Ponds were built in 1972
and are the largest in Northern Australia. Before this study, the knowledge of
pond bacteria was limited to the culturable Escherichia coli and enterococci.
Unfortunately, a focus on these bacteria misses the majority of resident pond
bacteria, their responses to the tropical environment, and the dynamics of
important bacteria like nitrogen cyclers.

My primary research objectives were to (1) identify the microbial community
composition in the ponds; (2) identify the genes and microbes responsible for
pond nitrogen cycling; and (3) investigate how the microbial community
responds to desludging. To address objectives (1) and (2), 288 wastewater
samples were collected at the inlet, middle and outlet of Sanderson Ponds 1,
2 and 5 in the morning (6 am) and afternoon (1 pm) during the early wet and
dry seasons. For objective (3), 96 samples were collected in a similar manner
from Leanyer Pond 2 before desludging and then one week, six months, and
12-months after. Measurements included both in situ physico-chemistry and
microbial DNA (or RNA). I used 16S rRNA gene sequencing to determine the
bacterial community composition and Functional Gene Array to determine the
activity of nitrogen cycling genes.

I found that bacteria typically associated with the human gut are replaced by
environmental bacteria as effluent progresses through the ponds and that IV
desludging improves the removal of faecal bacteria and nitrogen. The study
determined where and how nitrogen is removed from the pond system. For
each pond, I identified a unique fingerprint of faecal and environmental
bacteria-indicators that can be used for pond management and for developing
new tests for human faecal pollution in the environment. Thus, I demonstrated
that DNA-based detection methods can provide powerful and cost-effective
monitoring tools that can be used both by wastewater managers and
environmental regulators.

Date of Award2021
Original languageEnglish
SupervisorKaren Gibb (Supervisor), Keith Christian (Supervisor), Karen Gibb (Supervisor) & Anna Padovan (Supervisor)

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