Complete aerobic biodegradation of gasoline plumes near source is often not possible because the oxygen demand imposed (i.e. plume concentrations) exceeds the solubility of oxygen. Since gasoline constituents are known to readily biodegrade naturally, it may only be necessary to treat a fraction of contaminant mass flux. However, to implement what has been called enhanced in situ aerobic bioremediation, the challenge still remains to deliver as much oxygen as possible for a sustained period in a cost-effective manner.
Often, treatment systems must be installed close to the NAPL source, which results in a very high contaminant loading. This poses an unrealistic performance demand, and a more appropriate aim of remediation may be strategic mass flux reduction. Diffusive oxygen emitters (Ryan Wilson and Doug Mackay, 2002) can provide the desired oxygen release performance, and if deployed appropriately can result in a significant fraction of total contaminant mass flux reduction.