39    COMPARATIVE STUDIES OF ACTIVATED SLUDGE AND
ROTATING BIOLOGICAL DISC PROCESS
(II-MICROFAUNA)
Maria Hull, Lecturer
Ewa Klimiuk, Lecturer
Faculty of Water Protection and Inland Fishery
Academy of Agriculture and Technology
10-957 Olsztyn-Kortowo, Poland
Wojciech Janczukowicz, Fulbright Scholar
Department of Civil and Environmental Engineering
New Jersey Institute of Technology
Newark, New Jersey 07102
INTRODUCTION
Comparative microfauna investigations of different types of wastewater treatment plants lead to
the recognition of its specific development. Utility of this kind of investigation is greater if ecology of
one of the comparative systems is well-known and activated sludge can be regarded as such.' Recently,
the knowledge concerning rules of growth RBD biocenosis has enlarged,2 but is still not complete and
requires further experiments. Earlier comparative studies of activated sludge and RBD microfauna
were mainly qualitative.3 Trials of carrying out quantitative analogies probably encountered limitations in the methodolgy. RBD microfauna is not distributed within the whole volume of the film but
mainly in the thin, oxygen layer which is technically impossible to separate during the time of sample
taking. In this case, total film biomass cannot be the base for qualitative comparison with activated
sludge.
In the present paper, the amount of biofilm mass equivalent (EBM) to activated sludge biomass in
relation to organic load removed was the base (see part I of this article) and quantitative parameters of
disc microfauna were referred to it.
Comparative studies of activated sludge and RBD biofilm included: species composition, frequency, number and microfauna biomass.
METHOD OF MICROFAUNA EXAMINATION.
The investigations were carried out on a laboratory scale by using five tanks with activated sludge
and five (one stage) RBD reactors. The experimental units and technological conditions of experiment
are described in the first part of this paper.
Microscopic observations were started after twenty days of experiment and carried out for one
month with frequency 2-3 days. The biofilm was scraped of the first disc of RBD from 16 cm2 and
placed in 20 mL cylinder with 2 cm3 of water. After measuring the volume, the sample was blown
through by pipettes to obtain homogeneous suspension. The samples of activated sludge were taken
directly from aeration tanks.
Microscopic sections prepared from the volume of 0.05 cm3 of biofilm and activated sludge were
examined to describe microfauna species composition. The number of microorganisms was estimated
using 640x magnification for Zooflagellata and Rhizopoda, and 256x magnification for Ciliata and
Metazoa. According to the number of microfauna, the sample was diluted two, three, ten and fifteen
times. The average number from three repetitions was finally related to one milligram of dried
activated sludge biomass or to one milligram of dried biofilm mass equivalent to activated sludge (for
RBD).
Zooflagellata, Rhizopoda, Rotatoria and Nematoda were treated as complete systematic units,
however, Ciliata was examined as species.
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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