ARCHIVED REPORTS_XR0002480 - Laserfiche WebLink

Home Browse Search

CLEARWATER ' C R O U P Environmental SCrvICES 1 ' The water generated can sometimes be discharged untreated to local sanitary sewer distncts at relatively high cost, otherwise treatment is usually required prior to discharge to either a sanitary ' sewer, storm sewer, or re-injection If treatment is required, sites with relatively smaller problems are often best off using granular activated carbon The capacity of a large size aqueous ' carbon vessel will often be adequate for the duration of the project since gasoline mass recovery rates for groundwater extraction are usually very low rThe dissolved-phase plume beneath the site appears to be relatively stable however, therefore, the need for hydraulic control over the plume is only of minor concern The benefit of GWE at this ' site would be to lower the water table in order to expose contaminated soils to SVE These remediation systems are typically more monitoring and maintenance intensive than some of the ' other engineered technologies described above '• 6 3 3 Enhanced Bioremediation (In-situ) This technique enhances the natural microbial activity in the groundwater through the addition of dissolved oxygen Indigenous microbes use dissolved-oxygen to naturally breakdown hydrocarbons in groundwater Unless an additional source of oxygen is present, microbial activity in the presence of an energy source (hydrocarbons) usually occurs faster than dissolved ' oxygen can be replenished naturally through groundwater recharge If an energy source is not present, microbial activity will be minimal and dissolved-oxygen will not be depleted As a ' result, microbial activity tends to deplete the oxygen in the center of dissolved hydrocarbon plumes Once oxygen is depleted, anaerobic degradation predominates However, anaerobic ' degradation rates are much lower than aerobic degradation rates Thus, the rate at which natural biodegradation of the hydrocarbons occurs is restricted by the rate at which dissolved-oxygen can be replenished The addition of dissolved oxygen via air injection or chemical injection (i e ' hydrogen peroxide or magnesium peroxide) to oxygen-depleted areas allows degradation to proceed aerobically at much higher rates ' The direct addition of liquid chemicals such as hydrogen peroxide to raise dissolved-oxygen ' levels can be expensive, difficult to obtain permits for, and can be difficult to control, often requiring extraction wells in addition to injection wells Recently many sites have used Oxygen Release Compound® (ORC), a patented magnesium peroxide compound, in a solid form that is 1 ' ZB 1710 CAP 16 November 20,2002