ISCO v. AEROBIC BIODEGRADATION (GRO/BTEX)

The problem:  Soil and groundwater at the site are impacted with gasoline range organics (GRO) and BTEX (benzene, toluene, ethylbenzene and xylenes).   GRO concentrations were approximately 25 mg/L in water and over 600 mg/kg in soil, while total BTEX was 2,500 µg/L in water and negligible in soil.  The client wanted to compare aerobic biodegradation to in situ chemical oxidation (ISCO) using ozone and alkaline activated persulfate (AP-pH).

How PRIMA helped:   PRIMA conducted batch tests to assess contaminant destruction, measure soil oxidant demand, and assess the effect on secondary water quality such as Cr(VI) formation.  Aerobic biodegradation was evaluated using ambient air as the source of oxygen because hydrogen peroxide and commercially available oxygen generating compounds can inhibit biodegradation in laboratory studies (though they may work just fine in the field).  All three treatments successfully reduced contaminant concentrations, but both ozone and AP-pH generated Cr(VI).  The Cr(VI) naturally attenuated once the oxidant was consumed.  PRIMA advised its client that all three treatments were effective and recommended that aerobic biodegradation be used if practical since no adverse secondary effects were observed.