27    BIODEGRADATION OF PHENOLIC COMPOUNDS
WITH A SEQUENCING BATCH BIOFILTER
German Buitron. Research Leader
Jose Ortiz, Engineering Student
Environmental Bioprocesses Department
Institute of Engineering
National University of Mexico
C. U„ Apartado Postal 70-472
04510 Mexico, D.F., Mexico
ABSTRACT
Sequencing batch reactor systems have been used to manipulate both the organisms' distribution established in the reactor and the physiological state of the organisms developed, in particular they have been used to remove specific organic compounds present in industrial effluents. It
has been observed that a way to improve the bioreactor activity is maintaining a high biomass
concentration; i.e., using a biofilm system. This chapter presents the study of a sequencing batch
biofilter packed with a low cost material for toxic wastewater treatment. The packing material
was a porous volcanic rock (puzolane) with a mean diameter of 2.5 cm and 75% of porosity. The
water in the reactor was maintained at the laboratory temperature (15°C). A synthetic effluent
mixture of chlorophenols (60-400 mg/L) was used as the toxic wastewater model (phenol, 4-
chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol, 25% each). The mixture of contaminants was eliminated with an efficiency superior to 93% as total organic carbon and 99% as total
phenols. A maximal applied load of 3.6 kg COD/m3-d was achieved. The kinetic of phenols
degradation under starvation period was examined.
INTRODUCTION
Toxic compounds present in industrial wastewater are problematic to treat, due to the fact that
their concentration fluctuates with time (for example, during the washing of the reaction tanks in
the production unit). As a result, the microorganisms in a biological treatment are frequently subject to shock loading (and changes in concentration). In a continuous system, the microorganisms
are unable to acclimate to such fluctuations. Sequencing batch reactor systems have been used to
manipulate both the organism distribution established in the reactor and the physiological state
of the organisms developed; in particular, they have been used to remove specific organic compounds present in industrial effluents. It has been demonstrated that the periodicity imposed by
the operation of the system can overcome the impact of variations in the rate of electron donor
input to the system.1
A way to improve the bioreactor activity is maintaining a high biomass concentration; i.e.,
using a biofilm system.2-3 In the biofilm processes the inner layer of microorganisms is protected, tolerating the toxic shock loading.4 One example of these processes is the fluidized bed.
However, the disadvantage of such systems is their high energy consumption in order to maintain
in suspension the support, as well as the high costs associated with the optimized bed, generally
protected by a patent. Kaballo et al.5 compared periodic and continuous packed bed reactors
treating 4-chlorophenol. Organisms were more evenly distributed through the reactor operated
periodically. As a result, the sequencing batch biofilter was better able to treat large shock loads
(5-fold increase in the specific elimination rate per biomass unit) than the continuous flow
process.
52nd Purdue Industrial Waste Conference Proceedings. 1997, Ann Arbor Press, Chelsea, Michigan 48118. Printed in
U.S.A.
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