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DE 
The Dethlinger pond near Munster, a former mining pit for diatomaceous earth, was filled with chemical warfare agents during the Second World War and in the years that followed. This old armaments site is now to be remediated following careful planning (M&P Ingenieurgesellschaft mbH) and based on the test opening carried out in 2019. In autumn 2019, a total of 2,552 explosive shells were found in 120 m³ of excavated material during the test opening. The team of experts (M&P, Prof. Burmeier Gesellschaft, Heidekreis and GEKA) assume that the Dethlingen pond has a volume of 30,000 m³ and that around 30,000 pieces of ordnance need to be recovered. Before the pond can be opened, the groundwater must be gradually lowered so that the subsequent explosive ordnance clean-up can take place in dry conditions. Decades of contact between the groundwater and the munitions, some of which were leaking, meant that the water was heavily contaminated with chemical warfare agents, toxic decomposition products and heavy metals such as arsenic.
In future, the pit is to be enclosed by a 20 metre deep sheet pile wall so that no groundwater can flow in from outside the pond. The contaminated groundwater is to be pumped out via three extraction wells in the catchment area of the pond and purified in a multi-stage treatment plant from Züblin Umwelttechnik in accordance with official regulations so that it can be re-infiltrated outside the Dethlinger pond.
In the course of the multi-stage purification process, the groundwater is first neutralised by lowering the high pH value to the neutral range. At the same time, dissolved and oxidisable compounds are converted into filterable solids so that these can be removed from the water in the subsequent gravel filter. Further purification of the inorganic arsenic compounds and other heavy metals takes place with the aid of a special filter granulate. This is followed by two large water activated carbon filters. These form the main purification stage for the dissolved organic pollutants, which are bound by means of physical adsorption forces. The final treatment stage involves two ion exchangers to remove residual concentrations. A 15 x 24 metre prefabricated hall protects the plant from the effects of the weather.
The groundwater purification system operates fully automatically. The system is equipped with a programmable logic controller, a data acquisition system and a visualisation system. It is possible to intervene in the operation both from the plant and externally via a protected data connection. In addition, the system is equipped with a signalling device so that in the event of a fault, those involved are informed immediately so that suitable measures can be initiated immediately.
Groundwater purification and lowering are planned for at least the next five years. External monitoring of the groundwater purification plant will be carried out by M&P Ingenieurgesellschaft mbH over the next few years during the actual explosive ordnance decontamination.
Lower Saxony's Environment Minister Olaf Lies, Munster's Mayor Ulf-Marcus Grube and District Administrator Jens Grote put the groundwater purification plant into operation on 11 May 2022 with a joint push of a button. Prior to this, the remediation concept and the plant were presented by M&P Ingenieurgesellschaft mbH together with Züblin Umwelttechnik to the press, other stakeholders and representatives of the authorities.
Press:
BZ_2022-05-12-The contaminated sites will soon be tackled
(Source: Böhme Zeitung)
WZ_2022-05-13 - Dethlinger pond - Groundwater purification plant
(Source: Walsroder Zeitung)
https://www.ndr.de/fernsehen/sendungen/niedersachsen_1800/Niedersachsen-1800,ndsmag46608.html
(Source: NDR) from minute 12:40
#mupgroup #engineeringforabettertomorrow #MinisterofEnvironment #Dethlinger Teich #Commissioning #Groundwater purification plant #Fighting agents #Remediation
