The MDSE Mitteldeutsche Rehabilitation- und Entsorgungsgesellschaft mbH, as a project developer, permanently operates the hydraulic protection of the Freiheit III landfill site on the basis of an official order.
As the landfill operator, MDSE mbH is responsible for the proper lifting, collection and discharge of accumulated groundwater and surface water from the landfill area.
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The hydraulic protection of the Freiheit III landfill is intended to keep it largely dry by lowering the groundwater surface to 1 m below the bottom of the landfill, so that material leaching processes from the dump body into the groundwater are prevented.
For both geogenic and anthropogenic reasons, the elevated groundwater is highly mineralized water, which leads to considerable precipitations and deposits (mainly iron(III) hydroxide (brown), but also iron(II) sulfide (black)) in the entire system of well, pump and plant technology. In addition, the drop in performance of most wells is probably due to the fine-grain components contained in the aquifer, which are used by the operation of the well.
In order to maintain the performance of the wells and compliance with the defined subsidence targets, the approximately 30 m deep wells must be cleaned and regenerated at regular intervals.
MDSE is responsible for the operation of the technical systems for groundwater extraction and drainage as well as the client (AG).
The subject of this request is the following services for the regeneration of wells of the hydraulic securing of the landfill Freiheit III:
- annual regeneration of approx. 8 wells with start of performance in 2023
- Planning and preparation of work
- Implementation of service program at the wells with preparation of wells and preliminary investigations, well regeneration, follow-up investigations and restoration of wells
- Provision / discharge of rinsing water and sludge for recycling / disposal
- Documentation of services
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It is planned to conclude a contract for the regeneration of groundwater raising wells for a period of 4 years in the period 04/2023 to 03/2027.
The scope of services to be provided in principle can be presented as follows.
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1 Preparation of wells and preliminary investigations
The Contractor shall preserve evidence before the start and after completion of the work in the presence of the Client. Subsequently, the Contractor shall dismantle the well equipment as far as necessary in order to create the freedom to build.
Based on previous experience, it can be assumed that the well pumps will have to be replaced as part of the regeneration work.
The largest possible parts of the pump set should be pulled in one train by means of a crane (at least double pipe shot; Lifting height crane at least 12 m).
As preliminary investigations for the regeneration work, a TV examination and a plumbing of the wells are to be carried out. In this context, a short-term performance test to determine the well energy capacity is only to be carried out at the express request of the Client.
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2 Brunnenregenerierung
From the current point of view, modified cleaning methods are to be used for the Brunnen der Freiheit III, in which low-intensity energy inputs with controllable or switchable pulse generators only lead to a rearrangement of the grain structure of the filter gravel fill and thus the dissolution of precipitations and deposits is promoted.
The aim of the regeneration measures is to dissolve the performance-reducing soft to medium-hard precipitates and deposits present in the well filter and at the same time to convey them without damaging the filter gravel fill.
The well regeneration is to be carried out in several stages with the following process steps:
- mechanical pre-cleaning with brushes and optional removal of landings in the pump sump
- Pressure wave/pulse method with rigidly installed pump in the pump sump
- Optional operation: intensive removal with moving packaged pump in the filter area
- Elimination of landings in the pump sump
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3 Follow-up and restoration of the wells
As a follow-up to the regeneration work, as in the preliminary investigations, a TV examination is to be carried out to determine the well energy.
When restoring the wells after regeneration with assembly of all dismantled well equipment and E-MSR technology, only properly cleaned, tested and, if necessary, maintained parts and aggregates are to be reinstalled.
After completion of the work, the preservation of evidence is carried out analogously to the preparation of the wells.
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4 Treatment / provision / disposal of dishwashing material for reintroduction / disposal
In the regeneration capacities, rinsing material is produced as water-sludge-solid mixtures and sludge-solid-water mixtures (after sedimentation / separation). These mixtures are preferably to be reintroduced into the plant operation or recycled.
For this purpose, the items lifted from the wells during the work must be discharged into settling containers/containers and set down.
Alternatively, the Client may demand the disposal of the separated sludge-solid-water mixtures, which is why optional disposal services are requested in the specifications.
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5 Documentation of services
All measures carried out within the framework of regeneration must be fully and comprehensibly documented. The documentation of the work must be carried out in such a way that it represents a comprehensible and plausible basis for the acceptance of the services by the Client.
The documentation must be prepared separately for each well and handed over to the client digitally and in 1 copy no later than 1 month after completion of all on-site work of a campaign.