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Identifying Green and Sustainable Remediation Potentials by TAUW
Shortlisted for Best Overseas Project
A Case Study from a Complex Former Industrial Site in Brazil
The remediation of a former industrial site in the São Paulo Metropolitan area, a Brownfield on which an educational center was later constructed, in collaboration with partners from Brazil, Germany, and the US, highlights how the integration of sustainability practices can drive more innovative and efficient project outcomes.
Site Background
Following the rezoning of the industrial site to become an educational centre in 2000, soil and groundwater investigations revealed substantial contamination with chlorinated volatile organic compounds (CVOC). The site, formerly owned and operated by Philips do Brasil, hosted electroplating and degreasing area activities which are responsible for the contamination. TAUW’s Germany division and Grupo EPA, based locally in São Paulo, formed a cross-continental, multinational and diverse team in collaboration with Philips’s US division to address the site’s contamination.
There is a strict procedure for the management of contaminated sites specified and regulated by the São Paulo state environmental authority CETESB, which sets the legal framework in São Paulo. Guideline “Decisão de Diretoria (DD) no 038/2017/C” defines clear processes and procedures starting from several investigation phases, across a risk assessment based on CETESB standards and leading to an intervention plan which has to be submitted to the regulator. In this specific case, there is an ongoing separate legal process because the site is located in a designated “Critical Area” where the deep aquifer used for drinking water production is affected. Therefore, the District Attorney is legally pursuing the site owner to potentially arrange compensation for the environmental damage. In compliance with the DD, several investigation campaigns led to the delineation of four CVOC source zones on site - designated as Areas 1 through 4 (Figure 1).
Figure 1: Site of interest (left) and delineated source zones with contamination source and main contaminants of concern (right)
Intersection of social, environmental and economic sustainability practices
From the start of the project, our international team committed to maximize sustainability across the entire project lifecycle through the intentional and continuous screening of options based on the full sustainability spectrum — social, environmental and economic — with key sustainability indicators highlighted in Figure 2 below. These indicators and the sustainable development goals (SDGs) provided guidance and inspiration that encouraged the team to explore exciting, new ideas that transcend into further benefits within the three sustainability dimensions. These are presented in the following sections.
Figure 2: The three sustainability dimensions and common sustainability indicators
Multi-criteria analysis and CO2 calculation tool support decision-making
From a consultant perspective, major sustainability impacts can be made during feasibility studies. A core element here was the early involvement and engagement of project stakeholders such as the environmental authority, District Attorney, and the current site owner — and consideration of their needs and expectations in the planning process, respectively in the parallel legal pursuit. This basis for successful cooperation has since been strengthened through clear, transparent and proactive communication about site activities. Regular online meetings and site visits helped to keep all stakeholders involved and aligned throughout the project.
Earlier this year, our team delivered a guest lecture to Environmental Studies students discussing the ongoing remediation activities on their own campus. Future lectures are planned to provide students with deeper insight into the project's specifics and technologies used
To support the remediation selection, multicriteria analyses for sustainability assessment and the TAUW CO2 calculation were essential. The latter is a tool developed by TAUW for internal use that enables the comparison of different remedial technologies in terms of associated CO2 footprint. Additionally, the complex heterogenous soil consisting of alternating layers of sand/gravel and silt/clay and the limited spatial accessibility, as well as the ongoing public use and educational activities with their related safety aspects, played decisive roles in the selection process. Based on these criteria, bespoke tailored remediation actions with the best cost-benefit ratio were selected and subsequently designed to achieve the risk based remediation targets in each area of concern (Table 1).
Once the remedial planning foundation was established, various sustainable remediation practices were identified and implemented on site.
Use of solar energy to activate persulfate for ISCO treatment
With the goal of prioritizing green energy applications, a solar thermal system was used to heat-activate persulfate for use in an ISCO recirculation treatment in Area 1. This was chosen because (1) natural groundwater temperatures at São Paulo are comparably high at 20°C and therefore offer favourable conditions for heating to the target temperature of 50°C, (2) solar radiation in São Paulo is high so it was decided to use solar energy for the heating process. To do so, 18 solar panels were installed on the roof of the building adjacent to the treatment zone (Figure 3). A supplementary gas heater was available to compensate for natural variations in solar energy supply and guarantee heating to the desired target temperature. Heat was transferred to the oxidant solution via a heat exchanger to initiate activation of persulfate prior to distribution in the injection wells. This activation approach minimized the overall persulfate demand and no additional chemicals were needed as would have been the case with other activation methods.
Photovoltaic system will support power demand of treatment plant
A roof is currently being installed at the local water treatment plant (WTP) to provide protection for a chemical storage area. A photovoltaic system will be installed on the roof to support the power demand of the WTP ensuring efficient utilization of the space taken up.
Figure 3: Solar thermal panels installed on a building roof (left) and design for chemical protection roof equipped with a photovoltaic system (right)
Treated water is re-used in remediation processes
Processed water from the WTP is partially reused to prepare new oxidant solutions for the ISCO measures on site, conserving water from the public water supply system and reducing associated costs. Negotiations are currently underway with the neighbouring sports club to use the treated water for irrigation purposes which would add to the effective water reuse and simultaneously support neighbouring communities. Moreover, the treatment method was upgraded from UV radiation, previously installed and used by a former consultant, to compact air stripping units enabling less maintenance-intensive and more energy efficient treatment. Treatment components from the former system that are still functional, but not required in the new one anymore are considered for use in other projects in São Paulo state.
Excavated soil used in solid waste processing instead of disposal
Instead of conventional disposal, excavated soil from large-hole borings at a hot spot of Area 2 was sent to a solid waste processing company from the metal beneficiation industry which resulted in cost reductions of a factor of 6 to 7 compared to alternative incineration. Additionally, it allowed for the reuse of the soil for a different purpose as metals could be extracted from it and used in the metal industry.
Automized oxidant solution preparation saves time and costs
An automized oxidant preparation and dosing system for the ISCO recirculation measure at the Areas 3 and 4 was installed to avoid manual handling of the chemicals by field staff and optimize the preparation process (Figure 4). While improving health and safety conditions, the automatic dosing system also enables ISCO operation on weekends and holidays reducing the required remediation time by approximately 30%, which corresponds with supervision and operational efforts and thus costs.
Figure 4: Persulfate is delivered in big bags and lifted by a crane to be poured into a storage tank. From there, persulfate powder is added to the mixing tank as required to prepare oxidant solution of the desired dosage. Level sensors automatically indicate when new oxidant solution needs to be prepared.
Remediation successes to date and future efforts
After two subsequent ISCO applications at Area 1 in 2020 and 2022, an average concentration reduction of 98% for 1,1,1-TCA and 90% for TCE was achieved which verifies the efficacy of the presented green activation mechanism (Figure 5). The use of the solar thermal system to stimulate natural biodegradation is being considered as a polishing step. A DNAPL hot spot at Area 2 was effectively treated by 50 intersecting large-hole borings in 2023 resulting in an estimated mass removal of ~1,500 kg of CVOC. Subsequent ISCO direct push injections will target remaining smaller treatment areas in put into operation. The ISCO recirculation at Areas 3 and 4 using the automized persulfate mixing system will begin in mid-2024. The capture zone analysis based on hydraulic data, pumping tests and groundwater flow modeling suggests an effective containment measure at the southern site boundary preventing further down-gradient migration of the CVOC plume.
Figure 5: Average 1,1,1-TCA and TCE concentrations at Area 1 over the course of the ISCO treatment
The examples presented here demonstrate that implementing green, sustainable remediation practices not only offers more sustainable solutions, but more cost-effective and time-saving ones when implemented properly. In this regard, awareness, continuous striving and screening for optimization in terms of sustainability are the key drivers to find creative and innovative solutions that benefit the people, planet and prosperity.