31    SPATIAL AND TEMPORAL VARIATIONS OF
MONITORING PERFORMANCE PARAMETERS IN
HORIZONTAL-FLOW ANAEROBIC IMMOBILIZED
SLUDGE (HAIS) REACTOR TREATING SYNTHETIC
SUBSTRATE
Marcelo Zaiat, Ph.D. Student (EESC/USP) and Assistant Professor
Faculdade de Engenharia de Varginha (FENVA)
37010-540, Varginha, MG, Brasil
Lorena Grein Tavares Vieira, M.Sc. Student
Universidade de Sao Paulo (USP)
Escola de Engenharia de Sao Carlos (EESC)
Eugenio Foresti, Associate Professor
Universidade de Sao Paulo (USP) - Escola de Engenharia de Sao Carlos (EESC)
13560-250, Sao Carlos, SP, Brasil
INTRODUCTION
Bioreactors containing immobilized anaerobic sludge for wastewater treatment have been
widely studied for wastewater treatment aiming at the establishment of design and operational
parameters of full-scale units. Up-flow anaerobic sludge blanket (UASB) reactors and anaerobic
filters (AF) are examples of well-succeeded units that propitiate biomass immobilization. This
type of bioreactor provides conditions for the operation at high cellular retention time (CRT) at
low hydraulic detention time (HDT). As a general rule, this results in economic plants that combine efficiency with process stability.
Most of anaerobic reactor configurations containing immobilized sludge are developed essentially based on empirical criteria. The predominance of empirical over rational criteria arises as a
consequence of the variety and complexity of interactive processes occurring in such heterogeneous units. As a consequence, the study of fundamental phenomena can be very difficult. Moreover, the results obtained are often useless for designing, safe scale-up, or operational control.
Even so, the knowledge of some fundamental phenomena such as intraparticle and liquid-phase
mass transfer, intrinsic kinetic parameters, and reactor hydrodynamic would be useful for improving reactor's design and operation. Besides, these fundamental studies are essential to provide parameters for simulation and optimization of processes that make use of immobilized biomass.
The way the sludge immobilization proceeds also has influence in the choice of the reactor
configuration and process performance. In spite of several works reported on sludge immobilization in inert particles,'~5 the self-immobilization of anaerobic biomass is more attractive due to
its lower costs. However, the present knowledge of the self-immobilization process is not sufficient to guarantee its occurrence and control in adverse conditions.
A new configuration of anaerobic fixed-bed bioreactor, the horizontal-flow anaerobic immobilized sludge (HAIS) reactor, proposed by Zaiat et al.,7 was conceived to be developed under rational basis. A HAIS reactor containing immobilized sludge in polyurethane foam matrices was
first assayed for treating paper industry wastewater.8 A very short start-up period was observed
and the reactor achieved stable operation by the eighth day. During the experiment period, the
average chemical oxygen demand (COD) removal efficiency was 82% operating at the HDT of
9.2 hours and average temperature of 23°C. Afterward, fundamental aspects of the process were
investigated in order to obtain rational basis for HAIS reactor design. A sequence of experiments
51st Purdue Industrial Waste Conference Proceedings. 1996. Ann Arbor Press, Inc., Chelsea. Michigan 48118.
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