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Restoring capacity and water quality without dredging

When excessive sludge accumulation threatened the long-term health of Quellitzsee and risked disrupting one of Germany's most prestigious canoeing events, local authorities needed an alternative to costly dredging.

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Key Facts


The Challenge

Restoring Capacity and Water Quality Without Dredging

Quellitzsee is a popular recreational lake used for swimming, angling and watersports.

Over time, organic sediment accumulated within the lake, creating excessive sludge deposits and contributing to recurring cyanobacteria blooms. Local authorities determined that intervention was required to restore the lake and maintain its recreational value.

Traditional dredging was considered, but the costs associated with removing and disposing of the organic sediment made the approach difficult to justify.


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Why Oase?

Rather than removing the sediment mechanically, Oase proposed a biological sediment management strategy focused on accelerating the natural breakdown of organic material already present within the lake.

  • The objective was simple:

  • Reduce organic sludge accumulation

  • Restore water capacity

  • Improve long-term water quality

  • Reduce conditions that support algae growth

  • Avoid the cost and disruption associated with dredging


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The Solution

SchlixX Plus was applied across 15,000m² of the lake using a specialist application vessel.

Following initial challenges caused by unusually low temperatures, Oase developed an injection approach that enabled the treatment to penetrate deeper sediment layers and reach the target zone.

The treatment works by supporting biological decomposition processes within the sediment, helping break down accumulated organic matter while supporting overall lake health.



The Results

50-75% Reduction in Sludge

Monitoring showed a reduction of between 50% and 75% of the original sludge layer.

Sludge Reduced to 5-25cm

The original sludge deposits were reduced to a remaining layer of just 5-25cm.

Reduced Conditions for Algae Growth

By reducing organic material within the lake, a key nutrient source for algae development was also reduced.

Water Quality Maintained

Testing by authorities and stakeholders concluded that treatment successfully reduced sludge without negatively impacting water quality.

Long-Term Success

More than seven years after treatment, the lake remained free from further major incidents and no additional follow-up treatment had been required.


Key Outcomes

50-75% - Reduction in organic sludge

5-25cm - Remaining sludge depth

7+ Years - Without further treatment

Alternative to Dredging - Reduced cost and disruption

Quellitzsee demonstrates how addressing sediment accumulation at its source can improve water quality, restore capacity and support long-term lake health without the need for invasive mechanical dredging.



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