37    THE INFLUENCE OF RAW WASTES DOSING SYSTEM ON
TECHNOLOGICAL PARAMETERS OF ROTATING
BIOLOGICAL DISC (RBD) PROCESS
Wojciech Janczukowicz, Fulbright Scholar
Department of Civil and Environmental Engineering
New Jersey Institute of Technology
Newark, New Jersey 07102
Ewa Klimiuk, Lecturer
Maria Hull, Lecturer
Faculty of Water Protection and Inland Fishery
Academy of Agriculture and Technology
10-957 Olsztyn-Kortowo, Poland
INTRODUCTION
In biochemical processes, systems with step input of food to successive stages of biological reactors
in series are commonly known and used. It allows to control1 microorganisms growth in a more
proper way, creates better conditions for organic substrate utilization and for more uniform biomass
growth in all reactor stages.
In wastewater treatment technology, there are also known examples of step feed applying in
activated sludge process2, and in high-rate tower trickling filters.3 However, there is little information
available concerning the application of this system in RBCs.
In RBC, relations between amounts of biomass, organic substrate and dissolved oxygen concentration in every stage, are very important, because:
— the lack of oxygen in first stages limits the range of applied organic loading rate, and
influences formation of anaerobic layers in biofilm
— excess organic loading rate at first stage causes intensive biomass growth, what in
consequence can create some operating problems (with shafts and media)
Taking into consideration these phenomenon, the investigations on influence of wastes system
feeding in RBD on technological conditions and parameters of wastewater treatment processes were
carried out.
METHODOLOGY
The investigations were carried out using the experimental apparatus shown in Figure 1.
Synthetic wastes were used as the influent feed throughout this study. They were prepared by
adding commercial dry milk powder to tap water. Highly concentrated milk solution was pumped to
hydraulic mixer, where by mixing with tap water, wastes with required concentration were obtained.
Prepared wastes flowed by feeders to two four-stages RBD units. Table I contains a summary of the
detailed dimensions of RBD units used during two series.
In Control RBD unit, in both series, whole stream of wastes was conveyed to the first stage. For
these conditions, the same hydraulic loading rate was applied to all stages.
In Step Feed RBD unit, according to examined systems, raw wastes were conveyed to several initial
stages.
In series I, raw wastes flowed upon to the first three stages with the same flow rate (33/33/33
RBD). It was assumed that the wastes would not be conveyed to the fourth stage, because of necessity
of creating proper conditions for nitrification organisms.4.
45th Purdue Industrial Waste Conference Proceedings, © 1991 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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