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Effects of anoxia on protozoan communities in activated sludge operation

Donata Dubber

Donata Dubber

Supervisor: Prof. Nick Gray

Activated sludge, protozoa, anoxia

Protozoa play a varied and significant role in the treatment of wastewater by activated sludge. The increasing importance of altering oxidation-reduction potentials (ORP) as operational steps, in what has been a traditionally aerobic microbial process, has fundamentally changed the environment within the reactor and hence the dependent microbial ecology. The project examines varying ORP on the survival of protozoan species, and their evolution as communities, and how this affects performance, sludge production and quality. Enabling protozoan community structure to be predicted in relation to anoxia will permit more effective process management resulting in optimum treatment capability.


Dubber, D. and Harder, T. (2008) Extracts of Ceramium rubrum, Mastocarpus stellatus and Laminaria digitata inhibit growth of marine and fish pathogenic bacteria at ecologically realistic concentrations. Aquaculture, 274, 196-200.

Dubber, D. and Gray, N. F. (2009) Enumeration of protozoan ciliates in activated sludge: Determination of replicate number using probability. Water Research, 43(14): 3443-3452.

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Last updated 14 December 2009