Contaminated Soil ’88

The most relevant mechanism of toxicity of heavy metals certainly is the chemical inactivation of enzymes. Some metals may also damage cells by acting as antimetabolites, or by forming precipitates or chelates with essential metabolites. Soil biochemical processes considered especially sensitive to heavy metals are mineralization of N and P, cellulose degradation and possibly N₂-fixation1.

The available methods for the cleaning of contaminated soil do not always succeed in bringing the concentrations of heavy metals down to limits specified by the central government in the Netherlands [1]. A possible explanation is that the remaining metals may consist of a less mobile fraction of the overall contamination. A reduced mobility, however, implies that the residual concentrations possibly are more acceptable.

Many contaminants disposed on or immited into soil are highly reactive. In order to understand, quantify, and predict contaminant movement through soil, descriptions of the chemical processes in soil have been combined with transport models. However, despite unambiguous evidence concerning the variability of soil in the horizontal plane, with regard to e.g. the mineral and chemical composition and physical properties, few models were formulated to take such heterogeneity into account. For a proper risk analysis of the hazards of contamination for soil and groundwater it is important that spatial variability of the soil system is considered explicitly.In this contribution we show how spatial variability of soil properties may be quantified such, that it may be incorporated in risk analysis. With emphasis to heavy metals and phosphate, we give an impression of simple sorption functions, that are stochastic functions of distributed soil parameters, such as organic carbon content, pH, etc. By introducing these functions in the governing transport equations it is possible to evaluate the mean behaviour of a soil system, that exhibits pronounced spatial variability. For particular cases a very simple analytical approximation is developed. Leaching of Cu, Cd, and P is treated as an example, and we give quantitative evidence of the variability of soil properties controlling these leaching processes. As the method proposed is simple, and applicable to other contaminants as well (radionuclides, pesticides) it represents a powerfull tool for risk analysis.

The heavy metal kinetics are determined in relation to the water flow pattern, soil hydraulic properties, pH and soil chemical characteristics. Their depth distribution in soil and soil water will be simulated by a numerical model. Heavy metal contents in soil and soil water are gathered on an experimental field plot, located on the former Berlin sewage farms. Measured data will be used for fitting and validation.

Following the detection of contaminated sites the question is usually raised by what remedial measures future deleterious impact particularly on groundwater can be avoided. Similarly, for approval of new depositions of contaminated materials, authorities have to impose measures which “sufficiently safely exclude adverse long-term effects”. In both cases relevant criteria are lacking, particularly with respect for prognosis of long-term behaviour of pollutants.

In the recent years heavy metals in soils have become an increasing interest. The sorption of heavy metal ions is one of the most important solid and liquid phase interactions governing the processes of release and retention of these metals by soil /1,2/.

The gas production from charcoal (up till 1950) has led to a number of cases of soil pollution with cyanides. The reclamation of this polluted soil by excavation and incineration will be an expensive operation. The cleaning of cyanide-polluted soils costs about f 250,=/cu m with the present-day technics. Research is needed to develop new and less-expensive technics. First of all, more knowledge is required about the behaviour of cyanides in the soil. In this poster presented research was initiated and conducted by TAUW Infra Consult B.V. Results from batch and column experiments will be presented from two former gas works sites in Tholen and Zutphen, and effects of organic matter additions will be discussed on the behaviour of cyanides.

The Glimmerton (Miocene mica clay) is the first natural protective barrier of the deeper groundwater aquifers in Hamburg, The maximum thickness of this marine sediment is about 200 metres. In the area of the Georgswerder waste disposal Glimmerton thickness varies between 35 and 50 metres (BUSSE et al. 1985). In some undisturbed cores on the disposal site a number of different facies types with characteristic fissure structures could be differentiated (BRUNS 1986).

The Tertiary Glimmerton (Miocene mica clay), a silty and clayey, partly finesandy marine sediment effects in wide areas of Hamburg as an impervious layer and barrier between the partly contaminated upper aquifer and lower aquifers.

Several methods are available for cleaning-up soils contaminated with (heavy) metals, but none is 100% efficient. Their efficiency depends on type and characteristics of the soil, and on the chemical form and concentration of the metal. The methods used in this study were often less than 80% efficient, and sometimes even less than 50%.

The different chemical forms of metals in soils have generally-been investigated using sequential extraction procedures, indicating that the chemical form of the metals and soil characteristics largely affect their extractability (1). Because only certain forms of heavy metals are available to plants, one could expect, that extractable and available are the same. The purpose of this study was to assess the relative efficiency of different soil extractants for determining heavy metals in dredged material-soil mixtures and to determine if a single extractant could give a reliable prediction of plant-available Cd, Cu, Pb, Ni, Mn, and Zn.

Diffusion measurements as applied in radionuclide migration studies [1], offer also good possibilities to describe the behaviour of potentially hazardous components in soil, bottom sediments and waste materials, since suitable radiotracers or labelled compounds are available for several substances of environmental concern. At ECN the procedure for the diffusion measurement has been improved with the introduction of an interface marker and the simplification of the method to be able to perform large numbers of measurements on a wide variety of materials under a wide range of experimental conditions using a large number of components. The behaviour of trace constituents in the solid-liquid system can be studied under equilibrium conditions, when the radioactive “spike” is practically weightless, or with a concentration gradient of just one single constituent. In addition, the fractional distribution over liquid and solid can be obtained.

Contamination of groundwater by organic chemicals such as pesticides, industrial solvents and petroleum products has emerged as one of the major environmental problems in the 1980’s. In the United States, public recognition of this problem has led to regional and national legislation restricting the use and disposal of many compounds, a practice which is likely to expand in the future as groundwater monitoring programs gather more information. Attention has also focused recently on atmospheric emissions of volatile compounds which are added to the soil, or released as incineration byproducts.

Chemicals disposed from industrial and other uses are distributed in the environment into compartments of the atmosphere, hydroshere, lithosphere and biota. Fate of chemicals, that is, the distribution of chemicals to each compartment can be estimated from physical-chemical properties of chemicals, such as water solubility, partition coefficient(n-octanol/water), adsorption to soil and so on. Among these properties, adsorption of chemicals to soil has not been much investigated in comparison with other properties. This must be due to the tedious procedures of the measurement of adsorption of chemicals to soil. Also there is another reason that the difficulty of obtaining the soil which can represent as a sample of general soil.

The biodegradation of 22 specific organics have been investigated in the presence of sanitary landfill leachate and under aerobic and denitrifying conditions. All compounds except chlorinated alifatics were degraded under aerobic conditions. Chlorinated compounds, nitrobenzene and o-nitrophenol were generally more resistant to degradation. Aromatics with two- or more rings, phenol and 2-hydroxy-toluene were degraded very fast. Under denitrifying conditions only nitrobenzene and tetrachloromethane were degraded.

In order to determinate the danger potential of harmful substances concerning the biological — toxic characteristics of a chemical substance, its exposure behaviour as well has to be valuated. The valuation scheme at issue represents a classification of the mere substance specific migration behaviour of chemical substances (1).

Many studies have been carried out to modellate the behaviour of volatile organic compounds in the soil. Until now, only few studies have been conducted on sites with an allready existing soil pollution. These studies are necessary for validation of the models for practical use. A part of a study on the relation between soil pollution and indoor air pollution in 77 polluted houses and 20 reference houses (Fast et al. 1988), was carried out to evaluate the use of a soil transport model for describing the behaviour and transport of volatile organic compounds (VOC) through the unsaturated zone of the soil.

Benzene, toluene and xylenes (BTX’s) are often found as pollutants in soil and water. The mobility of these components in soil and groundwater depends on the geohydrological situation, but also on properties as volatility, solubility, adsorption and biological degradation. These properties are interrelated, in that the other features can be predicted from the solubility (1).

Chlorinated phenols are widespread industrial contaminants in soil. In order to get information on their fate in soil including total mass balances and mineralizatio, two representatives - 2, 4, 6- trichlorophenol and pentachlorophenol- were applied to soils in a 14C- labelled form.

The application of oily waste materials onto land has been a popular and inexpensive method of disposal used in the Canadian oil industry during the past 40 to 50 years. A variety of oily solid or semi-solid wastes have been disposed of in this manner including cuttings from drilling operations, sludges from the bottom of storage tanks or from gravity separators or biological treatment tanks and residues from flotation tanks. The potential exists for soil chemical and biological processes to degrade these oily wastes to end products that are innocuous and thus require no further treatment, however little information is currently available on environmentally acceptable methods for application for these wastes.

Several authors have studied sorption of nonpolar organics on soils, sediments, and aquifer material (1,2,3). On surface soils with organic carbon (OC) concentrations greater than 0.1%, the sorption was controlled by the fraction of OC in the sorbent. The sorption coefficient (K) for a compound on an unknown sorbent could be predicted from the sorbent organic content using the relationship K_oc = K/f_OC where K_oc is the OC normalized sorption coefficient, K the sorption coefficient, and f_OC the fraction organic carbon content.

A majority of the contaminated sites in the industrialized world involve a complex and unique mixture of soil, water and contaminants. There are no simple solutions and most remedial actions will take much longer than planned, be expensive and involve several technologies, each with its particular limitations and unknowns. We must continually learn from the experiences of others to reduce the time, risk and cost of remedial actions, while simultaneously meeting the objectives of environmental protection, human health and safety.

The study of contaminated land is relatively a new subject for the Commission of the European Communities (CEC) and for many of the European Community (EC) member countries. It is concerned with the contamination of soil with substances which, under certain circumstances, can be considered hazardous to the users or occupiers of the land; or detrimental to the fabric of buildings and structures in contact with the land; or pose a threat to surrounding soils and water and their associated flora and fauna.

“Contaminated land” is the term used in the United Kingdom to describe land that contains toxic substances in such concentrations that they present a potential threat directly or indirectly to man, to the environment or to other targets such as building structures. Land for development is in short supply and therefore there is pressure both from a social and economic standpoint to develop derelict urban sites which may be contaminated. Failure to recognise before redevelopment that a site is contaminated can be costly both in terms of financial resources and in relation to the risks to which the developers and the eventual occupiers of the site are exposed. There have been some notorious examples such as the Love Canal USA and Lekkerkirk Netherlands of the penalties which result from blindly developing contaminated land.

In order to increase the attractiveness of the conurbation Ruhr Area as a residential and industrial site the Land government of Nordrhein-Westfalen (NW) in 1979 has passed the “Aktionsprogramm Ruhr”. One emphasis of the political urban development concept in the course of the program is the “Grundstücksfonds Ruhr” (GFR); its task: reactivation of abandoned mining and industry sites for the urban development. “In order to excite the Ruhr Area’s plot market, to do away with plot defiles in individual cases and to reorder the gross cases of devasted landscape, abandoned work sites are acquired by the “Fonds” and are dressed and kept ready for a new structural utilization, being determined by municipal planning authorities” (Land Development Report, NW, 1982).

The nature of activities at industrial sites means that in almost all cases the soil will to a greater or lesser extent be encumbered locally with polluting substances. This may be caused by technical failures, spillage, or (various kinds of) human error. Even when the best available preventive measures (including the corresponding procedures for environmental protection) are used, a complete prevention of any adverse effects to the soil will be impossible.

The Nederlandse Aardolie Maatschappij explores for and produces oil and gas at numerous locations scattered all over the country and situated in various types of environment and on different types of soil. These activities are basically temporary, as after reservoir depletion the sites will be abandoned.Formerly accepted production and maintenance practices did not necessarily aim at the prevention of soil pollution, although incidental pollution usually led to ad hoc clean-up. In facing its responsibility for controlling the soil quality, the Company is presently developing a structural and fundamental approach to managing risks posed by the contaminants. This has resulted in a well-defined process of risk assessment, with the true objective of sensible risk managament. The basic principle is that of risk assessment of targets in and outside the locations, which are presently threatened or may be threatened when the contamination spreads. Targets include: human health, safety, equipment and facilities, and functions and usages of the soil.In this paper the principles of this approach to managing soil pollution are presented, including the methodology for development of site-specific clean-up criteria.

Soil contamination is a problem which concerns everyone. In recent years, this has resulted in the availability of a wide range of remedial action facilities. In the future, attention will, in the main, be concentrated on optimization of existing techniques for treating excavated soil (thermal and extractive treatment methods), on improvement and development of in-situ techniques and on isolation methods which are reliable during a defined period. Recently, particular importance has been attached to the biotechnological methods which can be adopted both after excavation as well as in-situ. These trends are already apparent in the extracts which were submitted for this conference.

The effects on different remedial action techniques on the original material are to be analysed. The analysis aims at obtaining characteristic values concerning mobilization of residual values of hazardous substancessoil chemicssoil physicssoil mechanicsreuse of treated material.

At the moment an extended research program, financed by the Ministry for Research and Technology and directed by the German Research Agency for the Environment is being carried out to undertake remedial action technologies on the landfill Gerolsheim.

The American Petroleum Institute (API) is a trade association with over 220 corporate members, and more than 5000 individual members, representing the integrated petroleum industry in the United States. Over the last decade, API has conducted many research studies investigating the fate of petroleum and its products in the environment. With the recent increased concern regarding soil contamination, API has focused many research projects on this environmental issue.

Since 1982 some flat wells for drinking and industrial water supply — situated in the Lower Terrace aquifier of the Rhine river — show contamination by cyanids.

This paper is based on current new research into seal wall engineering at the University of Hannover. I shall for reasons of time and space refrain from describing the known and often published systems and principles of seal walls. The results I shall be discussing concern the following problem: Approaches to testing suitablity of seal wall mass resistance to aggressive waste disposal seepage waters.Utilization of seal wall excavation material for producing flexible surface seals.Gas permeability of seal walls, test principles and trends of results.

The surface covering represents an effective element in encapsulating tips and contaminated sites, and as yet there is no established standard for its construction.As a general rule, however, the covering always exhibits the following elements: grass cover, top substrate (with surface drainage), sealing system, gas drainage and levelling layer.

Geotechnical data required to meet regulatory requirements for sound technical evaluation of soil compacted for waste containment liners or precipitation barriers in landfill cover systems are more stringent than those for most engineered soil structures. Unambiguous requirements for geotechnical parameters and measurement data are needed by both design/construction engineering firms and reviewing agencies so that the credibility of the data is clearly demonstrated. Data generated by laboratory soil testing to confirm design feasibility, and field performance testing of the structural and hydraulic properties of waste containment structures need to be evaluated from several perspectives.

A method for the securing of predominantly large old storages consists of their encapsulation with diaphragm walls. Such vertical locking is especially well suited when under the storage natural, low-permeation soil layers are found, into which the diaphragm walls are embedded. These diaphragm walls are, as a rule, produced in the versatile and low-cost cutoff wall procedure. The sealing wall masses used there must also be resistant to attack by seepage waters from the old storages.

In The Netherlands an increasing amount of attention is being directed to the application of soil covering systems as remedial action in contaminated housing areas.

For a number of years the refurbishment of contaminated sites has been considered as the most important task in the field of environmental protection. Strictly speaking however, apart from a few spectacular cases, efforts in this field have not really got beyond the testing stage of individual refurbishment techniques. In most cases the conventional method of enclosing contaminated sites provides effective remedy, particularly for groundwater protection.

The base sealing systems currently used in the construction of new waste dumps frequently consist of synthetic sealing membranes in the form of sheets.

In order to protect the groundwater, contaminated sites of former industrial plants or refuse deposits are frequently enclosed with sealing walls. This requires the existence of a continuous stratum of low permeability at a depth which can still be reached from the civil engineering point of view.

Two methods of underground sealing-systems were tested during the remedial clean-up of the industrial waste disposal site Sprendlingen: a cut-off wall with inserted welded HDPE-panels (Züblin system)a cut-off wall with replaced soil-concrete

Different mineral and artificial sealing materials find application for the encapsulation of hazardous waste landfills. The sealing function, however, must be accomplished as well as possible in the presence of all kinds of leachate solutions. Thus the transport processes for the contaminants can be reduced to a minimum with the help of the sealing materials. The materials used are compiled in Tab. 1.

Encapsulation of contaminated areas such as hazardous waste disposal sites by mineralic containment materials is widely in use. These measures of surface sealing or capping, subsurface horizontal sealing and of subsurface vertical sealing (cut off walls) demand the use of materials, which exhibit low water permeability, resistance to hydraulic preassure and chemical attack [1]. Thus, the spread of contaminants to the environment is to be reduced to a contaminant and site specific tolerable minimum. Our work deals with the assessment of the mobility and transport of hazardous chemicals through the containment materials.

Pollutant migration through seal elements of encapsulations occurs in the form of convection as well as diffusion.

Within the terms of a project funded by the Federal German Ministry for Research and Technology an innovative method for encapsulating wastes based on the diaphragm wall construction technique has been developed at the Gerolsheim Hazardous Waste Dump in Rhineland-Palatinate, FRG.

Surface sealing at the SWD-Gerolsheim has the objective of reducing the leachate regeneration rate and minimizing depot gas emission or, in other words, increasing the degree of gas capture. The selection and optimisation of the surface sealing system required is being carried out at present within the framework of the research and development project “Integrated Transferrable Research and Development Project for the Securing of the Sanitation of Special Waste Depots after the example of the Special Waste Depot at Gerols-heim/Rheinland-Pfalz” (funding — FMRT; liasion — Federal Environmental Office Berlin). The sealing systems are being investigated in test zones layed directly onto the body of the depot, in a two-stage programme involving the construction of altogether five test zones.

For the construction and the closing up of a disposal site in Schleswig-Hostein, on which formerly different waste was disposed and where today it is only allowed to fill rubbish, building rubble and gardening waste, a system for optimizing the most important factors for minimizing infiltration water is proposed (KNEIB, 1985).

Multi-layered surface covering systems are a common part of waste site containment. Their main purpose is to reduce the amount of infiltration water. The estimations of the amount of seepage reduction that can be achieved is mainly based on theoretical assumptions. In order to get realistic readings of the actual amount of seepage through covering systems a test area had been constructed on top of the Dreieich-Buchschlag landfill, which is situated 5 km south of Frankfurt am Main, West Germany.

The main goal of the rehabilitation of the abandoned landfill Hamburg — Georgswerder is to protect the surface and ground-water against hazardous leachates. So far, the contamination of the near-surface quarternary aquifer is low. The limits for drinking water are exceeded slightly only at a few points.

Along with the remediation activities on the waste disposal site Georgswerder in Hamburg a research and development program with regard to the water balance of several multilayered surface sealing systems is being carried out. For this purpose six large-scale test fields with a size of 500 m2 each were installed in the landfill surface sealing, which was set up in 1987. They serve to carry out a long-term observation of the Georgswerder cover and other systems which differ from it. The tests are supported by the BMFT and the City of Hamburg and focus on the comparative evaluation of the effectiveness of the different covering systems. The objective is to derive general suggestions with regard to the design and dimensioning of surface sealing systems and to develop technically uncomplicated controlling device to supervise their effectiveness.

The protection of water, especially groundwater against all kinds of contaminants, whatever their chemical concentration, solubility and physical mobility may be, must have high priority as it is proven that there is almost no biodegradation of these contaminants, and if so at all, this process is very slow. Up to now the groundwater was considered to be the safest water resource due to the filter-effect of the soil and thus was to be used for the production of drinking water in the future. However, this statement is not reliable any longer. It is therefore necessary to completely avoid jeopardy and the expansion of present contamination and to pay increasing attention to the groundwater by working on possible engineering solutions. In this respect various guidelines have been established, however it has become obvious that they are not suffficient enough. With regard to settlements, flexural bending performance, weld seams and embankments special requirements turned out to be necessary, which will be briefly explained hereafter. Underneath the backfill of a disposal the liner is exposed to high elongations and deformations and is expected not to be influenced in its long-term behaviour, even when chemical and mechanical stresses are added. This means that the elongation of a material may not have a negative impact on its chemical long-term resistance and its resistance to interchrystalline stress-crack corrosion.

In the last three years much research has been done on the development of biological treatment techniques. Currently, the landfarming method is in operation and is being in practice to remove oily substances. Biological treatment in situ is still in the stage of development and finds only limited application on a practical scale. Regarding the development of bioreactors most research is done on banch scale.

High concentrations of hexachlorocyclohexane isomers in soil-slurry were readily mineralized by the mixed aerobic microbial populations already present in the soil. Under actual field conditions, the same hexachlorocyclohexane isomers were present for decades and only very slow bio-degradation was observed. The formation of intermediates from their degradation led to increased groundwater contamination problems as well as acute toxicity problems towards higher animals such as fish.

The possibilities for treating polluted soils according to biotechnological principles were investigated. Although considerable rates of biodegradation have been obtained, the actual rate of decontamination of authentically polluted soils appeared to be limited by that of the mass transfer of the pollutant from the soil particles to the degrading microorganisms. The latter rate appeared to be influenced by the physical properties of both pollutant and soil.The rate of mass transfer will have to be increased if an economically feasible process is to be achieved.

At the beginning of the 70s, the problem of hazard waste sites already became a matter of political interest in the Federal Republic of Germany, owing to its inclusion into the ecological program of the Federal Government. Not until 1978, however, the concept of hazard waste sites and the problems connected with it became a topic of discussions concerning environmental policy, which was initiated by the environmental report of the Committee Of Experts At Ecological Questions. In 1982, the information paper “Danger Estimate and Reclamation Possibilities Of Hazard Waste Sites” was presented by a team of the “Waste Material Association”. In 1983, the OECD introduced the term “contaminated sites” as an expanded version of hazard waste sites. For the first time factory grounds were regarded as sites which might possibly be dangerous for the environment.

Biodegradation of hydrocarbons is well known since a long time (1, 2, 3). Remediation by biological methods in large scale nearby a waterplant is described by Nagel et al (4). The clean-up of a sandy aquifer polluted mainly with aromatic hydrocarbons by activating the indigenous microflora was already published by Battermann and Werner (5). The mineralization of mineral-oilproducts occurs naturally worldwide, as there are to mention spills from refineries, crude oil pollution on sea and so on (3).

An important part of the costs of soil clean-up is involved with excavation of the contaminated soil. These costs could be reduced considerably by an in-situ treatment of the location. In the framework of the Research Program on Biological Soil Clean-Up Techniques the Ministry of Housing, Physical Planning and Environment has assigned a research project to the RIVM in co-operation with the Division Technology for Society of TNO.

Remediation of hazardous waste sites can best be accomplished by combining biological, chemical and physical treatment processes with site management and engineering expertise to develop site-specific remediation systems. This paper presents three case histories where microbiological processes have been used as the keystone technology to develop cost-effective remediation systems for hazardous waste sites.

The degradation of aromatic xenobiotic compounds by aerobic bacteria is an important part of wastewater treatment (Alexander, 1980). There are different ways of gaining microorganisms which are able to degrade xenobiotics: Enrichment and isolation of bacteria with desired degradation capacities from soil and water samples (Cook et al., 1983; Amy et al., 1985).Improvement of strains for degradation of new substrates by mutation and selection (Kellog et al., 1981; Kiibane et al., 1982).Construction of degradation pathways for recalcitrant compounds by genetic engineering (Lehrbach et al., 1984, Chatterjee et al., 1982).

Chlorinated compounds are released into the environment due to their widespread industrial, agricultural and domestic use. Many of these compounds are present at low concentrations in water and soil samples and seem to be persistant. In our laboratory, sediment column experiments (Fig. 1) were designed in order to investigate the bio-transformation of tetrachloroethylene (PER) and all three isomers of trichlordbenzene (TCB) under anaerobic conditions.

The aerobic biodegradation of alpha-hexachlorocyclohexane (alpha-HCH) was studied in slurries of polluted soil. A bacterium which grows on alpha-HCH as sole carbon and energy source was isolated after enrichment. It was tentatively identified as Pseudomonas vesicularis. The organism grows on alpha-HCH with a mean generation time of about 6 hours. The substrate yield coefficient was about 60 g dry weight per mol of alpha-HCH. Growth, expressed as protein increase, was associated with the release of chloride ions, the decrease of alpha-HCH, and oxygen consumption. Fifty % of the carbon in alpha-HCH could be recovered as CO₂. These results suggest a complete mineralization of alpha-HCH. The maximum rate of biodegradation of alpha-HCH observed (1.35 mg.liter-1.minute-1) in comparison with its low solubility in water (about 5 mg.liter-1) indicate a high rate of solubilization of alpha-HCH in the culture medium. Inoculation of slurries of polluted soil with the isolated bacterium enhanced the rate of dechlorination.

The Greenbank Gas Works Site occupied approximately 10 ha of land to the east of Blackburn, England and was contaminated with coal tar, phenols, heavy metals and spent oxide containing complex cyanides which prevented redevelopment for intended industrial use. A scheme was devised by BioTreatment Limited of Cardiff to treat the material on site using a combination of conventional engineering and microbiological techniques to predetermined target levels in accordance with ICRCL (Interdepartmental Committee for the Reclamation of Contaminated Land) 59/83 a guidance document prepared by the U.K. Department of the Environment (DoE).

The Nederlandse Aardolie Maatschappij (NAM) explores for and produces oil and gas at hundreds of locations in the Netherlands, which are scattered all over the country and situated in various types of environment and on different types of soil. Activities at these locations are basically temporary, because the sites will be abandoned after the reservoirs have been depleted.Previous production and maintenance practices could not prevent the occurrence of soil pollution at several of these locations. To restore soil quality the Company is undertaking clear-up projects on locations where real identified risks are identified. To reduce clearn-up costs the Company is developing new clearn-up techniques, which are adapted to the particular circumstances. There circumstances are related to the site-specific activities, the type of contaminants and the time available for restoration. In order to test two potential promising techniques a project has been started at a location in the north of The Netherlands. The applicability of biorestoration for soil contaminated with volatile aromatic hydrocarbons and mineral oil will be tested. In the same project biological treatment of contaminated groundwater will be tested.The results of a technical feasibility desk-study for biorestoration and biological groundwater treatment on a gas treating/production plant, including an outline of both techniques are presented.

Heterocyclic aromatic compounds are part of many natural products and of chemical building blocks of e.g. herbicides. N-heterocyclic compounds, e.g. pyridine, picoline or quinoline or S-heterocyclics such as thiophene and benzothiophene can be found in coke effluents. O-heterocyclis are formed by the Maillard reaction. In contrast to carbon cyclic compounds the information regarding the bacterial degradation of heterocyclic compounds is rare (Berry et al 1987; Ensley 1984; Shukla 1984; Trudgill 1984). The formation of intensely coloured compounds is due to chemical side reactions, whose degradation might constitute a real problem. In most cases the substances are toxic already at low concentrations. Halogenated compounds are even more toxic (Naik et al 1972). Their decomposition often requires an initial photolytic destruction.

Many soils in the neighbourhood of nonferrous galvanising or painting industries, or after the application of sewage or harbour sludge to land, are severely contaminated with heavy metals as Cd, Cu, Zn, Ni, Cr, Pb etc. Treatment of these soils happens by extracting the metals with acids or complexformers. Later the elution solution had to be treated with physico-chemical methods for the elimination of the metals.

In 1982, the Federal Minister for Research and Technology, Bonn, awarded us the above order. Preparation of the site started in the summer of 1982.

The principle of thermal soil decontamination is simple. A contaminated soil is heated to temperatures of 400-700 °C, which is sufficient to evaporate or to pyrolyse the organic contaminants. The gaseous products are removed by convection and the residual soil is ready for reuse after cooling and moistening.

The Naval Construction Battalion Center (NCBC) in Gulfport, Mississippi was used as a storage and transshipment facility for Herbicide Orange (HO) earmarked for vegetation control in Southeast Asia. HO is composed of a 50:50 mixture of the N-butyl esters of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,4-dichlorophenoxyacetic acid (2,4-D). Following a 1971 EPA ban on the use of herbicides containing 2,4,5-T, remaining U.S. stocks of HO were delivered to NCBC for storage pending ultimate disposal. The ban was based on the trace level contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) present in 2,4,5-T. TCDD occurred at an average concentration of 2.0 parts per million in HO. The drummed HO remained in storage until 1977 when it was dedrummed, transferred to the incinerator ship Vulcanus, and subsequently destroyed by incineration in the central Pacific Ocean.

Serious contamination of soil was first discovered in the Netherlands at the end of the Seventies. In the beginning it was thought that this was just a one-off mistake from the past. The Government spent as much as Hfl. 200 million to remedy this single case of contamination. The money was used to purify the soil underneath 100 houses and, after a long stay in emergency accommodation, residents were able to return to their own homes.

The principles of some thermal and extraction soil cleaning techniques are briefly discussed and results of the treatment of contaminated soil on a large scale in the Netherlands are presented.A study of the performances of a thermal plant is discussed. In this study a testing procedure for the sampling and analysis of soil as well as an environmental audit are included. The latter will be used in the future as a frame-work for an environmental protection system designed for the soil cleaning sector.

Two companies, i.e. Deutag-Mischwerke GmbH and Von Roll Ltd have been engaged in the field of thermal decontamination of polluted soils for some time.

In December 1984 we took over a site in Hamburg from a former herbicide production plant for dismantling the manufacturing units and decontamination of the equipment and solid wastes, expecially soil.

Contaminated soil, abondoned waste disposal sites and polluted industrial sites from a major part of our environment requiring clean-up measures.

In the field of thermal soil purification the process developed in 1981 by Ecotechniek bv, Netherlands, demonstrates the highest technical standard at present. Approximately 500 000 t of contaminated soils were purified to date using plants of this type, the second generation of which was built in 1985.

Deutsche Babcock Anlagen AG is at present commissioning a plant with a throughput rate of 7 t/h for the decontamination of polluted soil.

Solid waste processed at the Peak Oil site is being incinerated in a transportable infrared incinerator, designed and manufactured by Shirco Infrared Systems, Inc. of Dallas, Texas and operated by Haztech, Inc. of Decatur, Georgia. The overall incineration unit consists of a waste preparation system and weigh hopper, infrared primary combustion chamber, supplemental propane fired secondary combustion chamber, emergency bypass stack, venturi/scrubber, exhaust system, and data collection and control systems all mounted on transportable trailers.

In innumerable cases of contaminated soil hazard or injury due to depot gas must be reckoned with. In the course of necessary sanitation measures recourse must very frequently also be taken to the method of thermal disposal of the gases (deodorization). As depot gas always contains, along with CH₄, CO₂, and air, also trace substances such as hydrocarbons, halogenated hydrocarbons and hydrogen sulphide, emissions occur after incineration, in addition to CO₂, H₂O and surplus air, of HCl, HF and SO₂ as well as of CO and unincinerated residues of organic compounds. In addition there is a possibility of formation of substances like PAH (polycyclic aromatic hydrocarbons) and PCDD/PCDF (dioxin/furane).

Once polluted soil is thermically cleaned up, a dead product is the result. However, the Dutch government emphasizes the so-called principle of multifunctionality of the soil. The most vulnerable function of the soil is the ecological function. To assess the possibilities of ecological recovery of cleaned soils, a field experiment was performed in a pasture on the grounds of the institute in Bilthoven. Because soil mesofauna plays an important role in the functioning of the soil ecosystem, colonization and development of free-living nematodes and other soil mesofauna was studied in enclosures consisting of thermically cleaned soil containing a core of unpolluted grassland soil. The core was added to study possible migration of mesofauna from healthy soil to the cleaned soil. Some enclosures were fertilized to improve environmental conditions. The controls contained no core, but only unpolluted soil or cleaned soil.

The disposal of cleaned soil often forms a problem. Although the soil is cleaned it still might contain residues of the pollutants. Thermically cleaned soil is a completely dead product. Therefore it has to be recolonized by plants, soil microflora and soil animals to become a normal healthy soil again. Addition of healthy soil or fertilizer to the cleaned soil may enhance the recolonization by living organisms. An enhanced recolonization rate may promote the acceptance of the cleaned soil by the general public, which makes it easier to dispose of the cleaned soil.

The remediation of contaminated sites is an increasingly serious problem in industrialised countries. There is a growing need for efficient techniques for remedial actions, especially for on-site treatment of hazardous waste sites.

For the purpose of this paper physico-chemical methods are defined as all remedial methods that remove contaminants from soil or destroy the contaminants in the soil, with the exception of thermal methods and microbiological methods. This definition excludes the methods which are aimed at the stabilization and/or solidification of contaminated materials; these are discussed in separate papers.

As you are aware, soil exchange has been the most commonly used form of land reclamation up to now.

What is being presented is an extractive soil-decontamination system developed in Berlin, the HARBAUER PB 2, which has been working on the contaminated grounds of Pintsch-Öl GmbH (in liquidation) since the summer of 1987 and has already cleaned more than 11,000 tons of contaminated soil at various locations. The experience and knowledge gained with the operation of this system are described, the state of the art explained and future perspectives outlined.

In situ techniques for cleaning of contaminated soil can be divided in: physical methodschemical methodsbiological methods

The objective of this study was to examine different techniques of excavating soil for incineration. Two excavation techniques are compared with their ability to remove soil in a cost-effective, environmentally acceptable manner.

A photopaper producing plant discharged Cd containing wastewater into two infiltration ponds in the years 1935–1955. Periodical flooding of these ponds caused a soil pollution with Cd in the adjacent dune plot. In the vicinity of the polluted area a groundwater-pumping station is situated.

In the years 1984 and 1985, the Battel le-Institute in Frankfurt investigated a presumably contaminated site on behalf of the Landkreis Gifhorn. The wastes (mainly construction materials, domestic waste and excavated soil) in the gravel pit contain a complex contamination by light fuel oil, heavy oil, aliphatic chlorinated hydrocarbons (CHC) and polychlorinated biphenyls (PCB) /1/. On top of the aquifer a funicular soil slick covering an area of about 5000 m2 with a vertical extension of up to 0.6 m was detected. In the groundwater a pollutant plume with a length of about 1 km was found, containing up to 10.000 ppm CHC.

The extraction of waste liquids for the effective supporting of an encapsulation requires the knowledge of some marginal conditions. These conditions can be determined by means of specific observation wells and pumping tests performed in such wells, if necessary in consideration of the laws of multiphase flows in porous media. As a part of a R+D-Project supported by the UBA, Berlin (“New Methods for the Clean-Up of Waste Sites with Particular Reference to the Georgswerder Waste Site”, part 6/1440390F0) such observation wells were installed in the Georgswerder Waste Site and tested. The results obtained are the basis for the dimensioning of extraction systems, which are to be built as a prototype on the waste site in oder to test their practical applicability.

6–7 tons tetrachlorethene originated from destination residues were deposited in a landfill which was working between 1942 and 1975. The whole waste volume was inquired to 150.000–200.000 m3. Based on route-indicator studies the landfill was a possible producer of a contamination with chlorinated hydrocarbons in different captures of spring in a more distant vicinity. In regard to the investigation of the actual risk potential tests were done to remove hydrocarbon vapors from the subsoil. Furthermore the tests should give informations about the remedial action technique using a soil-gas exhauster.

The group of pollutants, summarized as chlorinated hydrocarbons (CHC) is on the one hand characterized by a high hazerdous potential and on the other hand by a wide range of applications, which extends into numerous fields of industrial activity.

Water. which gets on a landfilled site by rain or landfilled waste. contaminates slowly with soluble salts and pollutants of the landfilled waste by leaching through the landfill site. The contamination is much more dangerous, if the landfill site contains in parts or exclusive hazardous waste. Therefore this leachat. which is collected by drainages and wells, is not alloud to go directly to a sewage plant; it previously has to be detoxicated.

The aim of treating organic liquids with sodium is to destroy organic compounds containing halogens, especially chlorides, and the separation of the sodium salts formed in the process, in order to be able to recycle and reuse these organic liquids to satisfy environmental regulations formulated for the F.G.R. The destruction of polychlorinated biphenyles (PCB’s), dibenzo-dioxines (PCDD’s) or dibenzo-furanes (PCDF’s) is of particular importance.

Solidification/stabilization (S/S) technology has been used for over 20 years to treat U.S. industrial waste.

Since from the economic standpoint, the storage capacity limits no longer allow the deposition of contaminated soils on disposal sites, it has become necessary to develop new methods to dispose of such soils. In future, research work ought to aim at developing techniques for in situ decontamination, and to investigate methods in order to prevent pollutants in the contaminated layers from penetrating into deeper layers, or into the groundwater. In the past, heavy contamination in the Ruhr area was caused by coking plant residues. Such plants produce coke by thermal disintegration of coal, the coke being used for metallurgical working of ore and in foundries. The main residual matters produced during the coking process are ammonia, benzene, and tar. Investigations made to date have shown that contamination occurred in places in depths of up to 10 m.

For the solidification of oily and contaminated wastes anorganic as well as organic fillers and binders were tested. The selection of suitable materials included the use of descriptive criteria (consistence, thixotropy, properties when immersed in water) as well as oil extruding tests, compressive strength tests, vane shear tests, leaching tests and stripping tests for volatiles. In addition sorption and de-sorption studies using hexachlorobenzene as a hydrophobic organic model micropollutant were performed.The anorganic binders and fillers showed little success; submersed in water, e.g., the solidification products decomposed to the phases they consisted of. Good success, on the other side, was found using organic solids such as natural asphalt or lignite powder. The quantity of solids necessary for successfull solidification, however, was relatively high (75 %). The sorptivity was considerably higher than that of inorganic materials. Consecutive desorption tests yielded indications, that above high sorptivity chemical bonding of the pollutants to the solids were established.

Many industries and mainly oil and petro-chemical industries, produce a lot of dangerous products. These wastes can neither be stocked on dumping soils, nor be incinerated; thus their combustion will bring out in the nature, some extremely poisonous gas. At present, they are stocked either in desert dumps, or in areas belonging to the owners of these wastes. Our firme has been specialized in the elimination of these dumps for now 10 years. Our first reference was the AMOCO CADIZ affair, in which we worked out 10.000 t. of waste on the beaches. Then we step in for manufacturers such as Naphtachimie at Lavera, or firms such as Gerland at Dury in the North, or financial groups and insurances companies such as Société Générale and U.A.P in the case of Bourron Marlotte. The solution we put into shape consists in the mixing of these toxic wastes with other chemicals, in order to get a perfectly neutral product which enables the restarting of the natural activity. For this type of works, we have shaped a team for several years. The equipment and the sub-contactors may be mobilized very quickly and our intervention average time is about 15 days. On top of a strong exprience, we work on the very spot of pollution without any transport of dangerous products; Each of our working sites has been supervised by official authorities. We stay at your disposal for visiting your sites or giving you some references delivered by official authorities: Most of the time, we offer a 10 years garantee of our work.