32    EMPIRICAL AND KINETIC MODELING OF
SOLID SUBSTRATE ANAEROBIC DIGESTION (DASS)
FOR JOINT MUNICIPAL-INDUSTRIAL
WASTE STABILIZATION
H.M. Poggi-Varaldo
Ecatepec Institute of Technology-TESE and P3 Consulting Engineers
P.O. Box 75-202, Mexico D.F., 07300, Mexico
F. Esparza-Garcia
Centre for Advanced Studies and Research (CINVESTAV)
Dept. Biotechnology & Bioengineering
Mexico City, Mexico
G. Fernandez-Villagomez
Centre for Disaster and Hazards Prevention (CENAPRED)
Mexico City, Mexico
S. Caffarel- Mendez
Ecatepec Institute of Technology-TESE and P3 Consulting Engineers
P.O. Box 75-202, Mexico D.F., 07300, Mexico
E. Arce-Medina
ESIQIE del IPN, Graduate School of Chemical Engineering
Mexico City, Mexico
ABSTRACT
Dry anaerobic digestion of solid wastes (DASS for the Spanish abbreviation of solid substrate
anaerobic digestion) is receiving much attention worldwide as an alternative for industrial and
municipal waste stabilization and reclaiming. Although some efforts were made in DASS
process modeling, they were concentrated on the thermophilic DASS and only addressed empirical or semiempirical models. This chapter, then, aimed at modeling the mesophilic steady-state
DASS process with both empirical and kinetic models.
Bench-scale, semicontinuous, mesophilic reactors were operated at six mass retention times
(MRT, 15, 18. 21, 25, 30, and 40 days) by duplicate. Process performance was evaluated in terms
of volatile solids efficiency removal, biogas productivity, methane content in biogas. volatile organic acids contents in mixed solids, etc. Methanogenic biomass was quantitated by coenzyme F
420 which is a factor practically specific of methanogenic bacteria. The feedstock was a mixture
of lignocellulosic wastes, food wastes, and biosolids intended to simulate the codigestion of industrial and municipal wastes. Empirical models based on Levenspiel kinetics were applied to
the efficiency and the unit removal rate of volatile solids. Another kinetic model based on the
conventional anaerobic digestion concept (as a series process hydrolysis/acidogenesis. volatile
organic acids uptake rate, and methanogenesis) was adapted and fitted to data.
The efficiency increased in the range 60% to 83% (biodegradable volatile solids base) with increasing MRT (18 to 40 days MRT). However, the efficiency was very poor (27%) at 15 days
MRT. Unit removal rate and biogas productivity increased steadily from 40 to 18 days MRT,
with a sudden drop of both responses at 15 days MRT. The overall performance indicated a partial process inhibition at 15 days MRT.
52nd Purdue Industrial Waste Conference Proceedings. 1997, Ann Arbor Press, Chelsea. Michigan 48118. Printed in
U.S.A.
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