Abstract: Reductive Dissolution and Precipitation of Manganese Due to Biodegradation of Petroleum Hydrocarbons
KLINCHUCH, LESLIE, Chevron USA Inc., Bakersfield, CA; THOMAS DELFINO, Geomatrix Consultants, Oakland, CA
Dissolved manganese affects the aesthetic quality of groundwater used for domestic purposes. Reducing conditions due to natural biodegradation of petroleum hydrocarbons in contact with groundwater can cause dissolution of manganese from aquifer sediments. However, the reaction is reversible by chemical oxidation downgradient of the bioremediation shadow. Geochemical modeling (MINTEQA2) predicts the redox conditions for manganese precipitation from groundwater, back to aquifer sediments. The reaction rate for manganese precipitation is related to the advective and dispersive transport of dissolved oxygen in groundwater. At a petroleum release site in central California, the reaction rate was observed to follow first-order kinetics. Knowing the site-specific aqueous geochemistry and reaction kinetics, measures can be taken with reasonable certainty to construct water supply wells to avoid producing water with unacceptable levels of manganese.
AAPG Search and Discovery Article #90911©2000 AAPG Pacific Section and Western Region Society of Petroleum Engineers, Long Beach, California