Practice question

Biosparging constitutes in situ groundwater remediation targeting dissolved and sorbed petroleum hydrocarbons in saturated zone where natural oxygen typically depleted below 1 mg per L. Technology injects air, pure oxygen or microbubble oxygen-emitters at pressures slightly above hydrostatic 5 to 15 psi through wells placed 5 to 10 feet below plume. Bubbles rising dissolve oxygen up to 8 to 10 mg per L per Henry's law and partition volatile BTEX upward to vadose zone for capture by soil vapor extraction. Aerobic bacteria Pseudomonas putida and Rhodococcus carrying xylene monooxygenase and catechol pathways exploit oxygen for initial ring activation otherwise rate-limiting. Design accounts for air channeling due to heterogeneity by using closely spaced points 20 to 50 feet apart, pulsed injection preventing biofouling and monitoring dissolved oxygen, oxidation-reduction potential and contaminant concentrations to verify radius of influence. Unlike bioventing treating unsaturated zone, biosparging prevents plume migration and protects downgradient receptors while promoting aerobic mineralization rather than slower anaerobic routes.