NAME
biomoc - A multispecies solute-transport model with biodegradation
ABSTRACT
BIOMOC is a two-dimensional model that can simulate the transport
and biotransformation of multiple reacting solutes. The program is
general and flexible, allowing for any combination of biodegradation
processes. A number of expressions for biological transformation
rates have been included as options in the code. These include
single, multiple, and minimum Monod kinetics and competitive,
noncompetitive, and Haldane inhibition. The kinetic parameters can
be formulated to simulate zero-order or first-order approximations
of biodegradation rates. The growth and decay of several microbial
populations performing the transformations is also accounted for.
The microbial growth can be disabled, limited by biomass inhibition,
or limited by the availability of a specified nutrient.
METHOD
BIOMOC is an extension of the U.S. Geological Survey's Method of
Characteristics (MOC) flow and transport model (Konikow and
Bredehoeft, 1978; Goode and Konikow, 1989). The two-dimensional
transport equation is solved for each solute species and a
biodegradation reaction term is included. The flow and transport
equations are discretized using a rectangular, uniformly spaced,
block-centered, finite-difference grid. Implicit finite-difference
equations are used to solve the flow equation. The average linear
flow velocities are then calculated and used to solve the transport
equation using the method of characteristics and particle tracking.
Macroscopic fluid substrate, electron acceptor, and cellular
nutrient concentrations are used to calculate uptake and growth.
Monod kinetics is used to represent biodegradation uptake that
depends on a single solute concentration. For biodegradation
processes that involve several solutes, two alternate modified Monod
formulations are included in BIOMOC. The multiple Monod formulation
assumes that the biodegradation reaction is limited by the
concentration of each solute involved in the reaction. The
alternative minimum Monod formulation assumes that a single solute
is limiting the process. In addition, the Monod parameters can be
specified to approximate zero-order or first-order biodegradation
rates.
All degradation kinetics formulations include competitive,
noncompetitive, and Haldane inhibition. Competitive inhibition is
used to represent the inhibition of uptake of a secondary substrate
when the primary substrate is still present. The noncompetitive
inhibition formulation is useful for modeling the transition between
redox zones within contaminant plumes; an example of noncompetitive
inhibition is the inhibition of an anaerobic biodegradation process
by the presence of oxygen. Haldane inhibition is used to model
toxicity. The biomass growth rate is proportional to the
degradation rate. However, growth may be either turned off or
limited by a biomass inhibition formulation.
BIOMOC does not include pore-scale processes and does not account
for the effect of diffusion into and out of the biophase. It has
also been assumed in BIOMOC that the biomass remains attached to the
sediments. Pore clogging by biomass growth is not accounted for.
HISTORY
Version 1.0 1999/03/10 - Initial release
DATA REQUIREMENTS
Input data consist of initial conditions, boundary conditions,
aquifer properties, and biodegradation parameters. See
documentation for details.
OUTPUT OPTIONS
See documentation.
SYSTEM REQUIREMENTS
BIOMOC is written in Fortran 77 with the following extensions: use
of variable names longer than 6 characters and use of include files.
The code has been used on UNIX-based computers and on DOS-based 386
or greater computers having a math coprocessor.
DOCUMENTATION
Essaid, H.I., and Bekins, B.A., 1997, BIOMOC, A multispecies solute-
transport model with biodegradation: U.S. Geological Survey
Water-Resources Investigations Report 97-4022, 68 p.
REFERENCES
Goode, D.J., and Konikow, L.F., 1989, Modification of a method-of-
characteristics solute-transport model to incorporate decay and
equilibrium-controlled sorption or ion exchange: U.S. Geological
Survey Water-Resources Investigations Report 89-4030, 65 p.
Konikow, L.F., and Bredehoeft, J.D., 1978, Computer model of two-
dimensional solute transport and dispersion in ground water: U.S.
Geological Survey Techniques of Water-Resources Investigations,
book 7, chap. C2, 90 p.
CONTACTS
Operation and Distribution:
U.S. Geological Survey
Hydrologic Analysis Software Support Program
437 National Center
Reston, VA 20192
h2osoft@usgs.gov
Official versions of U.S. Geological Survey water-resources analysis
software are available for electronic retrieval via the World Wide
Web (WWW) at:
http://water.usgs.gov/software/
and via anonymous File Transfer Protocol (FTP) from:
water.usgs.gov (path: /pub/software).
The WWW page and anonymous FTP directory from which the BIOMOC
software can be retrieved are, respectively:
http://water.usgs.gov/software/biomoc.html
--and--
/pub/software/ground_water/biomoc
If you would like to obtain the price of and (or) order paper copies
of USGS reports, contact the USGS Branch of Information Services at:
USGS Information Services
Box 25286
Denver Federal Center
Denver CO 80225
To inquire about Open-File Reports or Water-Resources Investigations
Reports:
Tel: 303-202-4200; Fax 303-202-4695
To inquire about other USGS reports:
Tel: 303-202-4700; Fax 303-202-4693
SEE ALSO
moc(1) - Two-dimensional method-of-characteristics ground-water flow
and transport model
moc3d(1) - Three-dimensional method-of-characteristics ground-water
flow and transport model