Topic Area: 2a. In Situ Bioremediation Applications

Formatted Title:

Environmental Bioremediation as a Polishing Technique in an Area Impacted by L-NAPL

Background/Objectives:

The study was conducted at a chemical industry located in São Paulo, SP, Brazil. The facility has been in industrial operation since the 1950s and occupies a total area of 67,000 m². Currently, the manufacturing area consists of approximately 30 buildings where production, maintenance, and administrative activities take place, in addition to four tank farms for bulk storage of various chemicals. The industrial activity involves the production of approximately 80 distinct chemical products for use in the construction industry. A series of environmental investigations were carried out on site, revealing a risk of vapor inhalation for workers in civil and industrial construction. The dual-phase extraction (DPE) remediation technique was applied, and the system operated until the technique's limitation was reached for the extraction of free-phase L-NAPL product. For polishing and risk mitigation, a primary remediation technique, pump and treat, was planned and implemented, enhanced by bioair sparging techniques for aerating the medium and reinfiltration of treated effluent enriched with nutrients. The goal of applying these enhancement techniques is to optimize the physical environment to facilitate the growth of heterotrophic bacteria already present in the medium, known as bioaugmentation. Physical treatment for the removal of free-phase L-NAPL, combined with the augmentation of bacteria that consume the contaminant compounds present in the physical medium, provides greater effectiveness in environmental remediation of the area and ultimately eliminates the risk to human health.

Approach/Activities:

After 13 months of operation of the DPE remediation system in the area, which removed 97% of the free-phase L-NAPL plume from the physical environment, a decision matrix was established to select the best intervention technique for the case, with pre-established criteria for the Brazilian market. The criteria used in the matrix include feasibility, performance in the impacted environment, ease of application, consequences of application, costs, historical use of the technique in similar cases, time required to achieve goals, technology, and sustainability. The selected technique, enhanced pump and treat with bioair sparging and bioaugmentation of the environment, was distinguished by its sustainability, feasibility, and ease of application, as it utilized structures and lines from the former DPE system. The system was designed to operate in the residual free-phase area, with three extraction wells, six treated and nutrient-enriched effluent reinjection wells, and 16 biosparging wells arranged around the extraction and reinjection area. The nutrients used were a mixture of urea and monoammonium phosphate, which were homogenized with the treated effluent before reinjection.

Antonio Distante

Affiliation

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(Group 1, Poster Board #66) Environmental Bioremediation as a Polishing Technique in Area Impacted by L-NAPL