Investigação e remediação de solos e águas subterrâneas contaminados: um estudo de caso na indústria química.

Abstract

The problems associated with soil and groundwater contamination have been considered of great importance for chemical and petrochemical industry in the last years, due to its environmental, legal and economical impacts. Therefore, increasingly, chemical engineers, occupying technical or management functions, have been involved in the solution and prevention of such matters. This work, specifically, deals with contamination problems caused by NAPL´S s (non-aqueous phase liquids), presenting the transport process of such contaminants in the porous media, also describing the remediation processes usually employed in such cases. Following, the transport phenomena of solutes in saturated media and associated equations are presented. A case study of NAPL contamination in a chemical plant is presented, describing its origin and local geological/hydrogeological conditions. The remediation process adopted for the initial phase of plume migration control, consisted of a low permeability cutoff wall associated with a pump-and treat system, aiming to avoid environmental impact in the local ecosystem. The monitoring program has demonstrated that the implanted containment has achieved this objective. As it is well recognized by specialized literature, the remediation of sites with similar characteristics, if exclusively based upon dissolved phase control, must take tenths of years, so additional remediation measures that can contribute to accelerate the remediation, are being adopted. The considered measures include an air sparging associated with a soil extraction system (AS/SVE), besides the evaluation of natural attenuation processes in the area. Plume transport was simulated using an analytical model. The modeling results confirmed that a remediation process was needed. A sensitive analysis was performed, using several combinations of increments in the parameters that correspond to source and dissolved phase decay rates, simulating what can happen using the AS/SVE system. The conclusion was that the envisioned remediation system optimization might contribute to accelerate the remediation and reduce the impacts of the problem.