The scandal, later unmasked as one of Austria’s biggest environmental criminal cases leaked out, when analyses in the Vienna Basin (region Ebreichsdorf) found alarmingly high CHC concentrations in groundwater. The contaminated area extended up to Himberg/Moosbrunn.

The Republic of Austria, represented by the Ministry for the Environment (BMLFUW) reacted fast. It decided to form a group of experts, which were to evaluate immediate measures. At that point, it was already obvious, that the safest way would be to recover the hidden "toxic barrels" as fast as possible.

Volume estimates made at that time of 800,000 m3!, which proved true when the landfill was cleared later, anticipated costs of about ATS 2 billion (about € 140 million)! The landfill operators declared bankruptcy and the Ministry simply did not have the funds.

The then Environment Minister Marlies Flemming and the experts appointed by her of the Vienna University of Natural Resources and Applied Life Sciences (BOKU), the University of Technology, and the ARGE Pauser Klenovec, Rohrhofer/ GWCC (which finally was commissioned with the management of groundwater treatment), had to act fast and according to the then state-of-the-art!

Thus, measures with an as rapid impact on the contaminated groundwater body as possible were taken. € 5.8 million could finally be raised for the project called "Safeguard Fischer Landfill", which started in 1989. These funds covered the construction of nine hydraulic barrier wells in the immediate run-off of the landfill, approx. 60 km of pipes (expensive, but recyclable cast iron pipes by TRM were chosen already then!), a groundwater treatment plant, and the operation costs for fifteen years (today they amount to about € 0.7 million/yr).

The principle was simple, but has been effective to this day. The hydraulic barrier wells discharge (after further expansion steps the volume amounts to 120 l/sec. today) the contaminated groundwater to the treatment plant, where it is purified to drinking water quality. This water is returned to the groundwater body via downstream absorbing wells and infiltration ditch systems.

To this day, the speed of project implementation is impressive. Only three months and a half lay between the "go" by the BMLFUW and the activation of the treatment plant (end of November 1989)!

Project manager Thomas Derntl (GWCC) reports on the "cocktail of pollutants" found: "In the case of the Fischer Landfill, we mainly found lacquers and residues of metal production mixed with household waste at a depth of 25 to 22 meters underground. In groundwater, the highest groundwater table lies at about 20 to 25 m underground, we therefore find mainly halogenated CHCs, but also benzene, toluene, and xylene compounds, which afford special cleaning measures.

The upper groundwater horizon was to be cleaned up. Underneath lies a denser layer, which has prevented the toxins from advancing to lower lying groundwater tables so far. The fact that the same groups of pollutants did or do occur not everywhere in the area is also problematic."

For this reason, the experts decided to build a hydraulic-barrier well system with separate feeding of every single well to the treatment plant. This is the only way to specifically treat each "mix of pollutants" found. Derntl: "For microbiologically degradable components, this is a biological pre-treatment, an interim ozone treatment plant and optionally a flocculation/sedimentation tank. As to CHCs, we use multi-layer filtration and activated carbon filtration. Before the purified water is infiltrated, it passes a UV disinfection unit to eliminate microbial contamination."

Well-known companies are involved in the safeguard project: GWT (installation of the treatment plant developed at the BOKU), KSB, Vogelpumpen and Grundfos (pumps), and Ebro (shut-off valves). As successor to the Environment and Water Management Fund, the Kommunalkredit Public Consulting GmbH administrated the budget, which is financed by contaminated land contributions.

Activated carbon (supplied by Donau Chemie AG) also plays a key role in the fight against CHC contamination. Chemically seen, it is practically chemically pure carbon that has an extremely large free inner surface (approx. 1,000 m2/g!). The excellent purification performance is produced from the physical principle of "adsorption", by which pollutants are locked in the pores via electrostatic interactions.

Armin Wagner (Site Manager Adsorption Technology of Donau Chemie): "In the case of the Fischer Landfill, there were two applications for our filter carbon. First of all in the framework of CHC elimination from groundwater, with the filters being installed in the last step of the treatment plant. Secondly, for the clearing of the landfill, which started by mid-2002.

In this connection the highly contaminated air/gas mixture emitting from the landfill has to be cleaned by the so-called BIOPUSTER process before its release to the atmosphere. Donau Chemie AG acted in this case as subcontractor of ARGE Belüftung Fischer-Deponie (PORR Umwelttechnik and Bilfinger-Berger)". Thomas Derntl adds: "Important in CHC elimination are life cycle and operating life of the activated carbon in the filter, since they are relevant cost factors!

This is also the reason for the microbiological pre-treatment upstream of the four filter lines. It prevents – with the exception of CHCs – biological compounds from reaching the carbon filters. We thus speak of a ‘not biologically activated wet filtration with activated carbon’! On average, we exchange the activated carbon filter four to six times per year (in peak loads up to 25 times).

For CHC elimination about 100 m3 of filter material are used at a certain time." EU-wide tendering preceded both the clearing (cleanup) of the Fischer Landfill launched in 2002 and the clearing work as such as well as site supervision. The winner was the ARGE Räumung Fischer-Deponie (consisting of Bilfinger-Berger, STRABAG, PORR, and ALPINE) and the ARGE Bauaufsicht (consisting of IUP and DI Zimmermann). In addition, a local ARGE Chemie (consisting of ACE and Water & Waste) was created for the accompanying chemical analyses.

Measures taken and the experience made in groundwater containment and cleanup of the Fischer Landfill over 15 years reach much further. On the one hand, because there are other abandoned sites with unknown content in the surroundings of the landfill. There too, hydraulic barrier wells and groundwater treatment plants already show positive effects on the groundwater!

For Karl Rohrhofer (GWCC), the international remote effect of this successful combination of water and waste management is particularly valuable, since innumerable "containment and cleanup cases" are pending in Southeast Europe in particular.

In addition, South America, too, shows a great interest in this knowledge. Regarding the reuse of the water treatment plant of the cleaned up Fischer Landfill, the expert refers to the idea of the establishment of a Competence Centre for Drinking Water Treatment, which could be used for the training and advanced training of national and international specialists!
(Source: aqua press Int. 2/2005, Mag. Christof Hahn)