Sourcebook of Alternative Technologies for Freshwater Augumentation in East and Central Europe


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<Sourcebook of Alternative Technologies for Freshwater Augumentation in East and Central Europe>

2.2 Remediation Of Polluted Groundwater

In Zahony, located in northeastern Hungary on the Ukrainian border, a large programme of groundwater remediation, expected to extend over a two year period, was recently begun. Because Zahony is an important railway transportation junction between Ukraine and Hungary, and because of the railway guage differences between the two countries, a significant amount of transshipment of goods takes place, including the pumping of liquid hazardous chemicals: hydrocarbons are commonly transferred from the Ukrainian wide-guage tankers to the narrow-guage tankers used in Hungary. Because no groundwater protection measures against the leakage from the pumps and rail wagons were installed, large amounts of potentially dangerous substances have been deposited onto the land surface, where they infiltrated into the soil and the groundwater, since the 1960s. Due to the importance of the Pleistocene aquifers to the freshwater resources of the area, the Hungarian State Railways engaged MÁVÉPSZER Ltd. and ELGOSCAR International Ltd. to identify the extent of the possible contamination and develop a mitigation plan.

The extent of the contamination was determined from data gathered from 20 observation wells and other production wells in the vicinity of the station. Well data were collected using a MGSZ geophysical probe. Soils data were also collected from 1 500 sites and examined on-site using an HNU-101 photoionizationic detector and OVA 128 gas chromatograph. These data indicated that 10% of the hydrocarbons were in solution while the balance were present as emulsions; 58% of the hydrocarbons were oils, and 6% were volatile aliphatics, including benzol and ethyl-benzol, which are very soluble and mobile in water.

The remedial programme determined for this site used ORS Scavenger pumps to remove free hydrocarbons from both the surface and deeper groundwater abstracted by the production wells. Removal rates range from 1 to 10 m³/m/day of hydrocarbons. The groundwater from the horizontal protection wells is also treated with enzymes, such as ENZIM-MIX®, containing 3% to 6% tenzids, which help to remove particulate hydrocarbons from soil granules. This biochemical process produces carbon dioxide and water from the hydrocarbon contaminants, while air strippers remove the soluble hydrocarbons. Activated carbon filtration is used as a post-treatment.

Technical Description

In situ remedial technologies are emerging from the experimental stage toward the stage of a mature technology. During the last five years, many contaminated sites in Hungary have been remediated using this type of technology. Contaminated sites can only be effectively remediated within a conceptual framework that develops a strategy suited to the infrastructure available at each specific site, with the aim of removing or containing the contaminated soil in order to prevent harmful consequences to other elements of the biosphere. Historically, excavation of large quantities of contaminated soil was the only strategy for soil remediation to prevent groundwater pollution. Sometimes, these soil treatments were accompanied by some form of groundwater remediation. More recently, a comprehensive approach involving groundwater treatment and groundwater protection has been adopted.

In situ physico-chemical remediation, combined with enzymatic biodegradation of hydrocarbons, offers particular advantages for sites where excavation is not feasible, for example, due to presence of buildings and other structures. This type of remedial treatment can be used at production well sites, including horizontal wells, and can be fully automated. Such an approach was used to provide on-site remediation of groundwater at Nagyoroszi following the breakdown of the 'Friendship II' oil transport pipeline. At this site, 2 400 m³ of oil-contaminated soil, with an hydrocarbon concentration of between 2 000 and 16 000 mg/kg, was cleaned over a 6 months treatment period. Soils at this site were cleaned of hydrocarbon contaminants to a depth of 1.5 m to 4.5 m.

Extent of Use

This technology has been used in Hungary and Poland.

Operation and Maintenance

This is an highly specialized technology requiring trained personnel and specialist equipment. Operation of this technology is usually undertaken by contractors.

Level of Involvement

This technology is implemented at the level of local administrations and companies.

Costs

Typical costs can exceed $1 million, as the remediation of groundwater is a data and time intensive process. The costs include the costs of planning and detailed site investigations ($72 000); equipment, wells, and water treatment systems ($650 000); staff time and monitoring for up to 22 months or more ($400 000); and, remediation of the pumping station site to prevent future groundwater contamination ($30 000), based upon the Hungarian experiences.

Effectiveness of the Technology

This method has proven very effective in the remediation of the kerosene-polluted soils and groundwater at the Ferihegy Airport, Budapest. The treatment efficiencies removed up to 90% to 95% of the hydrocarbon residue from the treated water.

Suitability

Contaminated sites can only be effectively remediated if a conceptual framework is developed that takes into account the infrastructure availability and specific site constraints. However, this technology is potentially suited for use in most areas of the region where hydrocarbon contamination of groundwater is a problem. Nevertheless, prevention of groundwater contamination is always the most appropriate course of action, given the difficulties and expense involved in remedial programmes.

Advantages

This technology provides in situ clean up, which is more energy efficient than other remediation methods.

Disadvantages

This technology is costly, and requires trained personnel to implement.

Cultural Acceptability

The technology is acceptable. Further Development of the Technology The technology is fully developed.

Information Sources

Petèr Kovac and Dr Kornèlia H. Kocsis, Felsö - Tisza - Vidèki Környezetvèdelmi Felügyelösèg, 4400 Nyiregyhàza, Szèchenyi u.19, Hungary, Tel. (36-42) 310 155, fax: (36-42) 310 713.

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