HBGC123D: a high-performance computer model of coupled hydrogeological andbiogeochemical processes

Groundwater flow and transport models have been used to assist management o f subsurface water resources and water quality. The needs of more efficient use of technical and financial resources have recently motivated the devel opment of more effective remediation techniques and complex models of coupl ed hydrogeological and biogeochemical processes. We present a high-performa nce computer model of the coupled processes. HBGC123D. The model uses a hyb rid Eulerian-Lagrangian finite element method to solve the solute transport equation and a Newton's method to solve the system of nonlinear, mixed kin etics and equilibrium reaction equations, Application of the model to a lab oratory soil column with multispecies tracer injection suggests that one ma y use the model to derive important parameters of subsurface solute fate an d transport. These parameters may be used for predictive purpose in similar field problems. To this end, we present a three-dimensional, hypothetical bioremediation simulation on an aquifer contaminated by CoNTA. The simulati on suggests that, using oxygen alone to stimulate the biodegradation of the contaminant, one may reduce the waste to 40% in 10 years. Using a refined mesh of this three-dimensional model, we also conduct a performance study o f HBGC123D on an array of SGI Origin 2000 distributed shared-memory process ors. Both the computational kernels and the entire model show very good per formance up to 32 processors. The CPU time is essentially reduced by 20-fol d using 64 processors. This result suggests that HBGC123D may be a useful t ool in assisting environmental restoration efforts such as waste site chara cterization and remediation. (C) 2001 Elsevier Science Ltd. All rights rese rved.