Support for countermeasures against groundwater pollution by organic fluorine compounds

Overview

Characteristics of groundwater pollution caused by PFOS, etc.

PFOS and similar chemicals have a chemically stable structure. This means they cannot be expected to biodegrade in the environment and are, therefore, highly accumulative. In addition, PFOS is said to invade groundwater and have relatively high mobility.
In order to formulate effective countermeasures against groundwater pollution by PFOS based on the characteristics discussed above, it is necessary to fully understand the chemical properties of PFOS, etc., the characteristics of the groundwater flow unique to the contaminated site, and the ground characteristics that control the flow. Furthermore, it is necessary to select a countermeasure method according to the unique characteristics of the site.

OYO Corporation provides optimal countermeasure programs for PFOS, etc., based on the abundant knowledge and technology which we have cultivated over many years of soil / groundwater pollution surveys and support for countermeasures.

Details of services

OYO Corporation PFOS Groundwater Contamination Remediation Program

The groundwater contamination remediation program proposed by OYO Corporation consists of identifying the source of contamination and determining the contamination area through a fact-finding survey, setting of the area to be remediated and remediation goals (including future predictions), implementing countermeasures, and monitoring.
However, since investigation methods and purification methods have not been established for unregulated substances such as PFOS, etc., OYO Corporations collect and examine as many cases and research results as possible from the few that are available. From the initial stage of the program, it is important to create a fact-finding survey plan which considers the properties of the applicable substances and the ground characteristics of the site. Furthermore, since standard values have not yet been established, the range and setting of remediation targets are also important points when selecting countermeasures.

1. Formulation of CSM and survey plan: Estimation of contamination scenarios

In anticipation of implementing countermeasures, we use risk assessment methods to deal with PFOS groundwater pollution. We estimate the contamination scenario that leads to the occurrence of contamination at the site based on information such as domestic and overseas contamination cases, knowledge, and ground information. We then create an initial conceptual site model (CSM) that contributes to the subsequent estimation of contamination risk and setting of remediation goals. Based on this initial CSM, we create a survey plan necessary for ascertaining the actual situation and designing countermeasures.

2. Ascertain the actual situation of groundwater pollution: Conduct field survey

Field surveys examine probable sources of contamination and the surrounding groundwater/soil. When setting remediation goals, it is important to correctly ascertain the geological structure that affects the flow of groundwater. In order to quantitatively ascertain the characteristics of groundwater and mass transfer, it is also important to implement various survey and test methods used in geological surveys according to site conditions. Furthermore, since PFOS and similar chemicals are used in many of our daily necessities, it is necessary to pay close attention to cross-contamination from the clothes and equipment of workers engaged in the survey. OYO Corporation prepares work procedures (for example, educating workers involved in on-site surveys) and thoroughly controls the quality of sample data.

3. Setting remediation goals: Estimating and predicting contamination risk

We create a 3D hydrogeological model based on the survey results. We then convert this model into a numerical model. Next, we perform a simulation by setting the permeability and the boundary water level. In order to predict and evaluate groundwater flow and PFOS behavior, we quantify the initial CSM and use a detailed CSM numerical model that reproduces the ground characteristics.
We determine the remediation target values and their ranges not only by considering the current situation, but also by considering the predicted extent of contamination spread in the absence of countermeasures, the predicted effectiveness of candidate countermeasure construction methods, and the actual state of groundwater usage.

4. Design of countermeasures and implementation of countermeasures

Generally speaking, a considerable amount of time and money are required for complete remediation of soil and groundwater contamination. This results in a negative impact on a variety of areas, including various business activities and social reputation. In particular, although various methods have been proposed for countermeasures against PFOS and similar chemicals, there are few techniques that are versatile enough to be applied in general. For this reason, when implementing countermeasures, it is necessary to select appropriate purification measures, etc., in consideration of the contamination status of each site. It is also important to properly monitor and evaluate construction progress and provide feedback for construction.

Development stage of groundwater control technology for PFOS, etc.

Future initiatives

Even as the regulation of PFOS is progressing, chemical substances that enrich our social life are expected to continue to be developed and manufactured in the future. New knowledge regarding the impact of chemical substances on the environment and ecosystems will be discovered, and related regulations will be established. At the same time, contamination from chemical substances discharged in the past may become apparent or be identified.
OYO Corporation has participated in many purification projects since the early days of soil and groundwater pollution problems. We have also been involved in measures against improper disposal of dioxins and 1,4-dioxane based on the Act on Special Measures Concerning Removal of Environmental Problems Caused by Specified Industrial Wastes. Based on this extensive track record and our own ground data, OYO Corporation always proposes the optimal purification program against the threat of new chemical substances (PFOS, etc.).