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PROBLEM ASSESSMEWF REPOWT 4800 West Frontage Road Manteca Catdomia 5 2.3.1 Air Stripping Air stripping involves the removal of organic compounds by increasing the surface area of the processed groundwater and volatilizing organic compounds by mixing the water with blowing air The most common air-stripping design is counter-current, packed-tower aeration Other techniques include vacuum stripping, aspiration stripping, steam stripping, cascading, or water fail aeration, diffuser striping, and surface aeration To remove compounds that are volatile at higher than ambient groundwater temperature, the air stripping system can be designed to preheat the water or is used in conjunction with a secondary treatment or polisher system, such as activated carbon Prior to choosing this method of treatment, flow rates, contaminant types and concentrations, groundwater chemistry, permitting requirements, and space and power requirements must be considered The air containing organic compounds is typically discharged from the system The air discharge should be modeled and permitted where required Similarly, treatment of the air used to strip compounds from the water may be required by the permitting agencies ' 5 2 3.2 Bioremediation Extracted groundwater may also be treated by use of an aboveground bio-reactor Bio- reactors utilize natural or specialized bacteria to remove organic contaminants through aerobic and anaerobic consumption and digestion processes Digested organic ' compounds are converted to biomass and harmless by-products such as methane, carbon dioxide, and inorganic salts The bio-reactor design depends on contaminant concentration and type, flow rates, and groundwater chemistry Groundwater is pumped ' from the subsurface and enters a container that contains a sludge or film with a high microbe population that is exposed to the liquid The reactor capacity is large enough to allow both sufficient surface area for the introduction of the microbes into the groundwater and a sufficient residence time for the microbes to metabolize the organic compounds The water may be pre-treated to adjust the pH and temperature, and to Iremove inorganic materials that may clog the reactor system or harm the microbes 5.2.3 3 Ultraviolet Degradation Ultraviolet (UV) degradation involves pumping extracted water through a UV light source Two methods of destruction of organic compounds utilizing UV light have been developed The first method utilizes either a natural or introduced hydroxyl radical source and a UV energy source to destroy organic compounds The UV light source frees hydroxyl radicals, usually from hydrogen peroxide or ozone, which then react with the organic compound to form carbon dioxide and a secondary by-product The second method of UV light destruction involves utilizing a plasma type UV light source with a focused wavelength This focused energy is absorbed by the organic compound, 90-097A PAR 15