2023 Volume 3 Pages 22-32
Illegal dumping of waste may directly lead to serious pollution problems because leakage and entry of chemicals into the environment are likely to occur. This article describes the environmental pollution caused by extremely large-scale illegal dumping of waste at two bordering prefecture sites in rural Japan and reviews the history and results of the implementation of technical measures to deal with the problem at one county site. The target pollutants are a wide variety of chlorinated volatile organic compounds (VOCs) and aromatic benzene due to the dumping of numerous drums containing waste solvents. From the geological characteristics and features related to the presence of contamination, site remediation was performed by applying a chemical method using lime and a combined method using pump-and-treat and bioremediation. This study describes the technical details of the soil and groundwater remediation over the years. Furthermore, we would like to consider what lessons should be learned from this long-running case of illegal dumping.
In the latter half of the 20th century, cases of environmental pollution caused by anthropogenic chemicals began to occur in several areas and sites of the world. Well-known examples include contamination of a residential area in Niagara Falls, USA, located on a chemical waste disposal site for VOCs and other chemicals used as industrial solvents (United States Environmental Protection Agency, 2023), and dioxin contamination in the area surrounding an agrochemical plant explosion in Seveso, Italy (Mocarelli, 2001); however, numerous such cases have been reported (United States Environmental Protection Agency, 2021). The Niagara Falls case in point is the famous Love Canal incident, which prompted the U.S. Environmental Protection Agency to enact the Comprehensive Environmental Response and Compensation Liability Act (Superfund Act) in 1980 to pay for the cleanup, and a trust fund was established. In the Seveso incident, contaminated soil resulting from the 1976 accident was sealed and stored in drums but went missing in 1982 and was found 8 months later in northern France. This case was the genesis of one of the later international agreements on the transboundary movement of hazardous wastes (UN Environment Programme, 2011). These types of large-scale pollution events were also a negative side of the remarkable growth of the world’s chemical industry, which increased dramatically after World War II. The key lesson from these contamination incidents is that the production of man-made chemicals inevitably leads to the diffusion of chemicals into the environment and excessive accumulation in some areas (Schwarzenbach et al., 2017).
The first example of large-scale illegal dumping of waste in Japan and the major social impact from the resulting environmental pollution occurred on Teshima Island in the Seto Inland Sea, an inner bay (Takatsuki, 2003). Illegal dumping started in the midterm of the 1970s. The area of illegal dumping was estimated at 69,000 m2, the volume at 560,000 m3 and the total volume of waste at 600,000 tonnes. The illegal dumping of various industrial wastes on the coastal areas of the island and the burning of open fires also characterised the spread of contamination. The dumped waste included shredder dust from automobiles, which at the time was not yet regulated by law, and various toxic substances ranging from hazardous organic compounds to heavy metals (Takatsuki, 2003). Huge government funds have been invested in the site remediation. After excavation, the mixture of waste, contaminated soil, and normal soil was loaded into specialised dump trucks and transported by specialised vessels to a different island (Naoshima Island), where thermal treatment was applied using high-temperature melting technology. Over 14 years of this cleanup work was completed until 2021; however, remediation works for contaminated groundwater continue.
Some examples of environmental impacts reported as a result of illegal dumping are shown here. A study of large-scale illegal dumping of waste and the resulting pollution of the local environment and human health effects has been found in Italy. In 2008, the Italian government made the Bussi sul Tirino area located in Central Italy, Abruzzo, as the Site of National Interest in need of environmental cleanup (Vitali et al., 2021). Various industrial wastes containing hazardous chemicals such as dioxins and heavy metals were illegally dumped there for more than 20 years since 1984. As the area where the waste was dumped had abundant water resources from rivers and groundwater as a source of drinking water, there was strong concern about the impact of the waste dumping on human health. However, the results of analyses of environmental samples such as air and water, food samples such as eggs and biological samples such as human urine, conducted 15 years after the illegal dumping had ceased, did not reveal any particularly high concentrations. The key to explaining this result was considered to be the sedimentation process and retaining of substances for a long period of time (Vitali et al., 2021).
Another case was also in Italy and was due to illegal dumping of various types of waste. In Southern Italy, during the past years, an illegal practice of industrial toxic and solid municipal waste dumping occurred in the Campania region including Naples (Mazza et al., 2015). A huge amount of waste has been dumped in agricultural areas and other areas, and was also burned in the field. Mazza et al. (2015) reviewed studies on chemical contamination of environmental and biological sample surveys based on several literatures. The study also considered the impact of incineration facilities built during the illegal dumping. The results showed that the concentrations of hazardous substances in environmental samples were all below the standard values, and similarly, their concentrations in biological samples were also below the standard values.
Furthermore, a case of illegal dumping of various types of waste such as construction waste and municipal waste has been reported in Slovenia, mainly in the suburbs of its capital, Ljubljansko (Breg et al., 2008). This could be attributed to the urbanisation of the area. The dumping of 100,000–200,000 m3 was conducted at more than 1,000 dumping sites of various sizes. As in the case of Italy, the level of contamination of the local environment by hazardous substances was moderate. However, as the area is a water source, environmental remediation is considered necessary, while public awareness of the environment needs to be raised to prevent future illegal dumping.
Although not illegal (as was the dumping mentioned above), open dumping has become a normal waste disposal strategy in several developing countries, and the pollution burden on the surrounding environment has been a constant and serious concern. As an example, a report was made on groundwater contamination due to open dumping of municipal solid waste in Pakistan (Usman et al., 2017). According to the report, the groundwater measurements at six locations up to 500 m away from the dumping site reported very poor environmental data, with pH ranging from 7.5 to 8.2, total dissolved solids from 1,400 to 1,000 mg/L, arsenic from 52 to 105 mg/L and faecal coliforms from 20 to 200 MPN/100 mL, among others. Data on heavy metals and toxic substances are unknown, but the situation is presumed to be very alarming. This example shows that even normal waste treatment can be a serious threat to the environment in certain countries and regions.
The focus of this study is on environmental contamination stemming from large-scale illegal dumping of waste and its long-standing cleanup process in Japan. Illegal dumping along the border between Aomori and Iwate prefectures in northern Japan began in the early 1990s. An industrial waste disposal company in Hachinohe City, Aomori Prefecture was illegally dumping the industrial waste that it received from a similar company in Saitama Prefecture located in the Tokyo metropolitan area. On-site investigation and guidance by a public health centre began in 1994, and detailed surveys of contamination began in 2000. The waste-generating enterprises connected with the site were located primarily in the Tokyo area; however, ranged across entire Japan from Hokkaido region to Kyushu region. The location of this site is shown in Fig. 1.
Map of the site of illegal dumping at the border of Aomori and Iwate prefectures in Japan
In reviewing the above national and international cases, it can be said that illegal dumping of waste directly leads to the pollution of the environment by various chemicals. As seen in several past cases, disposal of waste containing hazardous substances can cause widespread and severe environmental contamination. Although remediation methods vary widely, this study provides a detailed technical review based on the remediation history of the Aomori–Iwate border site. Emphasis is placed on the history of the remediation practices of contamination in the site of Iwate Prefecture over the past two decades. The following information is provided: the type of waste dumping, type of environmental pollution caused by dumping, how the cleanup was planned and conducted, and finally the current status. Furthermore, we would like to consider what we can learn from this long-running case.
The dumping site was located on a gently sloping plateau at an elevation of approximately 450 m, spanning both Aomori and Iwate prefectures. However, the Aomori side had a large difference in elevation. In the late 1980s and early 1990s, the aforementioned company contracted with other companies to dispose off various waste materials from the far-flung Tokyo metropolitan area in Japan. Although some of this waste was converted into fertiliser and other resources, considerable amount of the product was dumped on its property on the border of the prefecture, along with several other unprocessed materials. Table 1 summarises the approximate quantitative data and qualitative characteristics of the dumped wastes.
| Dumping area (ha) | Dumping volume (m3) | Manner of dumping | Types of waste illegally dumped | Topographical features | Groundwater | |
|---|---|---|---|---|---|---|
| Iwate side | 16 | 2.5×105 | The disposal could be characteristically divided into 16 compartments. Among the diverse wastes, one characteristic was the large amount of chemical waste. | Food waste, plastic waste, refuse derived fuel-like waste, combustion residue, drums with solvent waste, sludge, oil waste, manure-like waste, bark, poultry manure, clinical and medical waste, and others. | The site was located on a ridge at a relative high altitude. Except for rainwater, water was unlikely to flow in from surrounding areas. Water may have flowed to the old river channel in the northeastern region. | A boring survey confirmed that the groundwater level was roughly 7 to 8 m below the ground surface. The groundwater aquifer was estimated to have a thickness of more than 10 m. |
| Aomori side | 11 | 6.7×105 | A large variety of waste was disposed of in a dispersed manner over the entire area. | Waste mainly composed of bark compost, waste mainly composed of incineration ash, waste mainly composed of refuse-derived fuel, waste mainly composed of sludge, clinical and medical waste, and others. | The altitude was relatively low. Water flow was observed mainly in the swampy area. | The groundwater level was about 7 to 15 m below the ground surface. The groundwater aquifer was estimated to have a thickness of more than 10 m. The groundwater generally flowed towards the central valley and to the west. |
A major characteristic of the illegal dumping on the Iwate side area was that combustion residue mixed with oil waste, bark compost, and chemical wastes such as several types of solvent wastes were found at concentrated spots. This had caused serious soil and underwater pollution around the dumping site, as shown in Fig. 2. In particular, contamination with numerous different VOCs was confirmed in the zone where a large number of drums containing solvent waste were buried. In several places, VOCs were detected in very high concentrations from the soil and the groundwater. It was therefore decided that the restoration efforts would be preferentially implemented as part of Iwate Prefectural Government’s initiative to restore the illegal dumping sites.
Planar map showing the approximate distribution of a variety of wastes (Considerable amount of the waste was mixed with large amounts of soil)
Table 2 shows examples of measured VOCs in both soil leachate and groundwater samples from the contaminated site at the time the contamination from illegal dumping was revealed. From these data, two major characteristics were found in regard to environmental cleanup at this site. First, a wide variety of VOCs was detected in soil leachate and groundwater above their respective elution or environmental standards. Environmental standards in groundwater also exceeded for heavy metals. Most of the VOCs were chlorinated solvents, with dichloromethane measured at the highest concentrations. Second, benzene, a non-chlorinated solvent, was also found in fairly high concentrations. Thus, the substances contained a mixture of organic solvents with considerably different properties.
| VOC | Concentration in soila) (mg/L) | Concentration in groundwater (mg/L) | |||
|---|---|---|---|---|---|
| Maximum | Mean | Maximum | Mean | Environmental standard | |
| Dichloromethane | 1.1 | 0.30 | 92 | 34 | 0.02 |
| Carbon tetrachloride | 0.0078 | 0.0011 | 0.039 | 0.011 | 0.002 |
| 1,2-Dichloroethane | 0.041 | 0.017 | 1.3 | 0.48 | 0.004 |
| 1,1-Dichloroethene | 0.013 | 0.0044 | 0.037 | 0.015 | 0.02 |
| Cis-1,2-dichloroethylene | 0.12 | 0.066 | 9.0 | 3.0 | 0.04 |
| 1,1,1-Trichloroethane | 0.054 | 0.022 | 1.1 | 0.50 | 1.0 |
| 1,1,2-Trichloroethane | 0.0058 | 0.0012 | 0.0097 | 0.0037 | 0.006 |
| Trichloroethylene | 0.44 | 0.14 | 5.5 | 2.3 | 0.03 |
| Tetrachloroethylene | 0.62 | 0.18 | 2.7 | 1.8 | 0.01 |
| Benzene | 0.11 | 0.061 | 6.8 | 2.8 | 0.01 |
These VOCs are difficult to degrade under general environmental conditions, but when certain environmental conditions are formed or engineered, degradation may proceed (Acton and Barker, 1992). Previous research studies have shown that chlorinated VOCs are more susceptible to degradation or dechlorination in reducing environmental conditions. In the 1980s, groundwater contamination by chlorinated solvents caused by advanced industries such as semiconductor manufacturing had become a problem for environmental pollution; however, anaerobic column reactor experiments had already shown that tetrachloroethylene could be decomposed under methanogenic conditions and mineralised to CO2 via trichloroethylene, dichloroethylenes, and chloroethylene (formally called vinyl chloride: VC) (Vogel and McCarty, 1985). In contrast, it is generally accepted that benzene is easily biodegraded under aerobic conditions but is less likely to degrade under anaerobic conditions in bioremediation technology for soil remediation (Alexander, 1999). These different features were a major consideration in designing the site remediation method and procedure. Indeed, in the remediation of soil and groundwater contamination caused by chlorinated solvents, the main issue is how to perform anaerobic bioremediation effectively (Matteucci et al., 2015).
As mentioned in the previous section, the contaminated waste dumped at the site was very diverse in terms of chemical composition. In addition, because the waste was widely mixed and distributed with the soil, it was clear that removing the waste in its mixed state and disposing it externally would result in mass processing and enormous expenses. Therefore, the basic policy in the prefecture was to conduct cleanup at the dumping site and to remove the toxic materials completely on-site, which was the in-situ cleanup strategy.
However, in applying the on-site remediation method, the following important issues were considered: 1) Understanding the composition of the soil layers and the characteristics of each layer, especially water permeability; 2) Understanding the existence of groundwater veins and their flow direction and 3) Understanding the distribution of various contaminants within the subsurface layers.
Fig. 3 shows an aerial photograph after the site was cleaned up in both prefectures over a period of 4–5 years. The area contaminated by VOCs on the Iwate Prefecture side, which is the subject of this paper, is referred to as “Zone N” for convenience. The process of deciding on a remediation method for this area is described in detail below.
Aerial photo of the illegal dumping area taken on June 5, 2008 during the period when the remediation work was approximately 4–5 years advanced
Fig. 4 (a) shows the distribution of VOC concentrations in the above zone, with the high concentration points reaching several tens of mg/L. Fig. 4 (b) is a horizontal cross section of (a), showing the distribution of the strata. The four soil layer types, namely, buried soil, loam soil, pumice, and tuff breccia, and their hydraulic conductivities are shown in (b) as a table. Of these, the coefficient of permeability determined by an in-situ test of the loam soil layer was 8.7×10–6 cm/s, which was considerably smaller than that of the other soil layers. As a geologic factor, this was one limiting factor in the selection of remediation techniques.
Status of distributed contaminant concentrations (a) in Zone N and the geological characteristics before remediation (b). In (a), the dark pink coloring in Zone N indicates a concentration contour map for VOCs. The yellow coloring outlines the location of the heavy vehicle access road at the remediation site. The light blue area indicates the location of the buildings including stock yard of wastes where the various waste materials excavated throughout at the remediation site are sorted.
In selecting the technologies to be applied, proposals for potential remedial technologies were solicited from several companies, and the most appropriate technology was selected by considering the following: 1) Different technologies should be applied to the non-saturation and saturation zones in light of similar physical and chemical properties of the VOCs (especially chlorinated ones), combined pollution, permeability and on-site workability. 2) It is necessary to consider the constraints on on-site construction and to achieve purification within a limited time period. Therefore, the first technique that was chosen was the agitation mixing of quick lime for the non-saturation zone. In the on-site facility after excavation, VOCs were evaporated and removed with the use of heat generated from the reaction between moisture in the pollutant and quick lime. The area to be purified was estimated at approximately 2,000 m2, the maximum excavation depth was 8 m, and the amount of soil to be excavated was 13,500 m3. 3) For the saturation zone, it was deemed appropriate to start with groundwater purification in a short length of time. The pumping and aeration method was mainly adopted in addition to bioremediation to perform purification for a rather long period.
As discussed in the previous section, it was determined that a reasonable strategy of remediation was to separate the small permeable aquifer from the upper non-saturated layer. The remediation technique applied to the non-saturated layer was the volatilisation and expulsion of VOCs by mixing the contaminated soil with quicklime. In Zone N, numerous drums containing waste VOC solvents had been excavated prior to this cleanup campaign and taken off-site for disposal.
During the treatment with quicklime, when excavation began again before the start of the project, approximately 340 drums containing waste solvent were newly found. As a result, the drums were excavated and removed from the site using larger drums that could hold the drums that had been buried, as shown in Fig. 5.
Waste drums found in the soil to be remediated (a) and their encapsulation in larger drums (b)
Pre-tests in the laboratory were conducted to determine the amount of quicklime sufficient to volatilise the VOCs from an economic standpoint. The change in soil temperature after mixing the quicklime is shown by the addition ratio in Fig. 6. The temperature increased to over 45°C under the condition of 7% (W/W) addition to soil. However, the condition of 5% (W/W) addition was chosen as an actual application. In contrast, the elution concentration of tetrachloroethylene determined by the standard elution test was high at some sites (approximately 60 mg/L); thus, removal of the material was expected to be difficult using this mixing treatment. Therefore, we tested how far purification could be achieved by increasing the amount of chemicals added. In this case, the chemical addition ratio was increased up to 14% (W/W), and the eluted concentration of tetrachloroethylene was 6 mg/L. However, this result indicated that the purification was insufficient. Therefore, the relevant areas were appropriately excavated and treated off-site. Although the amount of soil content after the remediation process was not specifically disclosed by the entity conducting the remediation work, it was inferred that the purification was completed in compliance with the soil contamination standard of Japan (Ministry of the Environment, Japan, 1991).
Addition rate of CaO and temperature changes of the soils
The contaminated aquifer from the saturated layer had high concentrations of chlorinated solvents and benzene. Therefore, the pumping and aeration method was applied as a physicochemical technique capable of reliably purifying aquifers (Calza et al., 2015). Then, from a long-term perspective, the plan was to switch to a bioremediation technique once purification had progressed. This switch in technological approach to bioremediation was conducted when the concentration of VOC constituents in the groundwater was below a level of 50 times the environmental standard. Fig. 7 shows an image of the pumping and aeration technology and the actual application scene conducted in Zone N. The upper non-aquifer layer had already been excavated and treated with chemical mixing in a covered space on the site. The protrusions visible on the surface (Fig. 7 (b)) are purification wells that were installed at 4-m intervals. In the actual treatment, there were considerable differences in the concentrations of contaminants within Zone N. Therefore, some areas were shifted to the bioremediation method after the pump and treatment was applied. Other areas were treated with the bioremediation method from the beginning of the cleanup after preliminary application tests were conducted.
Pumping and aeration technology for the saturated aquifer—Application image (a) and actual application scene in Zone N (b)
Fig. 8 shows the contaminant concentrations measured in a transitional monitoring well at the early stage of the cleanup process. In this treatment, an anaerobic environment was maintained by injecting organic nutrients from the middle of the period, and thus, decomposition by indigenous microorganisms was also believed to have occurred. Dichloromethane had the highest concentration, with cleanup starting at the 100 mg/L level. The next highest concentrations were of trichloroethylene, tetrachloroethylene, carbon tetrachloride, 1,2-dichloroethane, and cis-1,2-dichloroethylene. The concentrations of these substances generally decreased, and after approximately 1 year, the concentrations dropped to a few tenths of the original levels. However, none of the substances declined during this period to the levels that would meet the environmental standard. For example, the groundwater environmental standard for dichloromethane is below 0.02 mg/L, the level was a few mg/L (Fig. 8). The groundwater environmental standard for both tri- and tetrachloroethylene is 0.01 mg/L, but these were still between 0.1 and 1.0 mg/L. The pumping treatment began at around mid-June 2009 for approximately 2 years, and this was the method of cleanup during the initial 6 months. The concentrations of contaminants were reduced to almost 10 times above the environmental standard.
Example of concentration changes of VOCs by the pumping and aeration treatment observed at a well in Zone N
Biological remediation was conducted by adding commercial organotrophic substances containing carbohydrates, vitamins, and amino acid compounds to the injection wells among the wells shown in Fig. 7 (b). This stimulated the growth of native microorganisms in the aquifer under anaerobic environmental conditions. As noted in the previous section, before starting actual treatment on the site, biodegradation tests for the chlorinated compounds were performed in the laboratory. Because the concentration range of the substance to be decomposed is the most influential factor for the success of remediation efforts, tests were performed under both high and low initial concentration conditions. The results for initial concentrations were approximately 10 mg/L or less that corresponded to lower concentration range were shown in Fig. 9, and the concentrations of dichloromethane, chloroform, trichloroethylene, tetrachloroethylene, and cis-1,2-dichloroethylene were clearly reduced. However, depending on the substance, it took tens of days or more to achieve sufficient concentration reduction.
Concentration changes of chlorinated compounds in the laboratory biodegradation experiments
An analysis of the effect of this bioremediation on the rate of microbial degradation and other effects of purification was conducted for Zone N by Fukunaga et al. (2017), and the following conclusions were reached. Compared to the earlier estimated degradation rates of chlorinated ethylenes under natural conditions in groundwater, their first-order rate constants at this site were estimated to be up to 40 times higher. As an example, their same rate constant for trichloroethylene was estimated to be 0.001–0.040 (d−1). These values were obtained from an analysis spanning 1,020 days and a difference interval of 1 day for calculating the reaction rate at a concentration measurement interval of approximately 90 days. Similarly, the rate constants for chlorinated ethanes such as 1,1,1-trichloroethane were up to 35 times higher and those for dichloromethane up to 17 times higher. The rate constants for benzenes were also estimated to be up to 15 times higher, indicating that degradations under reducing conditions occur for dichloromethane and benzene, which are more likely to be accelerated under aerobic conditions.
The environmental factor of oxidation–reduction potential (ORP), which shows the oxidation and reduction states in the groundwater, reflects the progress of biodegradation in aerobic and anaerobic conditions. Data representing this are shown in Fig. 10 as iso-potential diagrams for changes in ORP and the concentration of each compound in groundwater during the 2-year remediation period. In April 2009, before the purification process began, the ORP profile showed that several ranges were positive except for the central area. After 1–2 years, ORPs fluctuated in the negative range, and by January 2011, they were significantly negative in more than half of the range of Zone N. The profiles of contaminants dichloromethane, tetrachloroethylene, and benzene also changed to low concentrations. At the beginning of the remediation action, there were high concentration spots for dichloromethane and benzene at 400 times higher than the environmental standards. These concentrations dropped to almost the same or lower than the environmental standards in the second half of 2011. These facts showed that benzene can be degraded under a reductive environment as well as chlorinated solvents (Dou et al., 2008, 2010). As a result, it took approximately 7 years to clean up the site, Zone N, with the monitored concentrations of contaminants fluctuating up and down relative to environmental standards.
Changes of oxidation–reduction potential (ORP) and the concentrations of three major pollutants expressed as iso-concentration diagrams during approximately 2 years of purification
When the cleanup for VOCs in Zone N was completed, exceedances of the environmental standard for substance 1,4-dioxane became noticeable in other zones of the contaminated site (Hem et al., 2013). In 2009, a new groundwater environmental standard was established for this substance. The source of contamination was estimated to be solvents in buried waste. The standard value of the compound is 0.05 mg/L in groundwater; however, it was detected at a concentration of up to 5 mg/L in the well that had the highest concentration. For this material, groundwater pumped from the site was purified using an advanced ozone oxidation technique at an on-site water treatment facility, and the treated water was injected into wells. Highly contaminated areas were remediated by injecting an oxidant into the soil, mixing it, and allowing it to oxidise and decompose. After approximately 7 years of cleanup measures for 1,4-dioxane, the remediation is almost at the point where completion is possible.
Through the above experiences in remediation, the following lessons were drawn:
1) It is important to determine the type of contaminants, their physicochemical and biochemical properties and concentration distribution from a broad perspective.
2) It is important to quantify the geological characteristics of the site, especially permeability, and to get as much information as possible about groundwater flow profiles, although there are always unknowns, and to link these to remediation decisions.
3) It is necessary to know the limits of on-site remediation and to consider the application of off-site treatment if necessary in light of temporal constraints.
The author hopes that this report will be of some help in the cleanup and restoration of contaminated sites caused by waste.
This paper is based on the results of the committee organised by Iwate Prefecture for environmental remediation at illegal dumping sites over a period of approximately 20 years of deliberation and implementation of measures. The author would like to thank the organisations involved for their cooperation during this research.
