ARCHIVED REPORTS_2011 REVISED FEASABILITY STUDY

Home Browse Search

TECHNICAL ATTACHMENT 131 Air Sparging Feasibility Assessment Nestle USA, Inc.- Ripon, CA 1.0 INTRODUCTION This potential feasibility of applying in-situ air-sparging (IAS) to remediate dissolved chlorinated hydrocarbon compounds in groundwater beneath a portion of the City of Ripon's Waste Water Treatment Plant (WWTP) is assessed herein. This assessment has been performed to be consistent with the technology screening phase of the Feasibility Study (FS) process by evaluating the technology's potential effectiveness, implementability, and cost (EPA, 1988). Section 2.0 includes a description of the IAS technology, including factors that seriously limit the effective implementation of IAS for groundwater treatment beneath the WWTP area; the potential effectiveness, implementability and cost of IAS is evaluated in Section 3.0; Section 4.0 summarizes conclusions from the feasibility analysis; and Section 5.0 includes a list of references. 2.0 TECHNOLOGY DESCRIPTION The two primary contaminant removal mechanisms for IAS application include: volatilization (physical removal of volatile organic compounds [VOCs] by in situ air-stripping) and enhanced biodegradation (Johnson, 1998). In stripping based IAS applications, VOCs in groundwater are volatilized into the injected air stream and transported to the vadose zone where they are collected with a soil vapor extraction (SVE) system. Stripping based IAS is a physical removal process and was not retained in the original FS and therefore is not considered further here for the same reasons. A variation of stripping based IAS is referred to as `biosparging'. Biosparging essentially is a traditional IAS system, but the focus is on VOC removal by biodegradation, not stripping, therefore eliminating the need for the SVE system. For biosparging applications, air is injected at a lower flow rate (compared to stripping based IAS applications) or in a pulsed manner with a goal of increasing dissolved oxygen concentrations without mobilizing contaminants into the vadose zone. Increases in dissolved oxygen can stimulate the in situ destruction of certain VOCs that are susceptible to aerobic biodegradation. When biosparging is used to treat large VOC plumes, the sparge wells are typically oriented on an alignment approximately perpendicular to the mean groundwater flow direction to create a zone of biodegradation that spans the plume width. This orientation, typically referred to as a `biobarrier', is a possible configuration for a biosparging application in the City of Ripon Wastewater Treatment Facility (WWTP) area where the intent would be to curtail the southerly migration of chemicals of concern (COCs) in groundwater. Biobarriers are used for dissolved AMEC Geomatrix, Inc. \\oad-fs1\doc_safe\9000s\9837.006\4000 REGULATORYTS Assessment_Apx B_012711\Attachment B.1\Attach B1.doc 131-1