Restoring marine health in the Marmara Sea with GEOTUBE dewatering

Overview

The Kocaeli Metropolitan Municipality together Republic of Türkiye Ministry of Environment, Urbanization and Climate Change, responsible for environmental and infrastructure projects in the industrialized city of Izmit, embarked on a large-scale dewatering project using GEOTUBE^® technology to combat severe marine pollution. The project was initiated in response to the 2021 season outbreak, which had devastating effects on Turkish tourism, marine biodiversity, and fish populations in the Marmara Sea. The root cause of this environmental disaster was the accumulation of industrial and municipal waste in the Kocaeli Bay, an enclosed water body with limited currents, making it a significant contributor to pollution across the entire sea.

Challenge

One of the primary challenges of the project was the highly variable composition of the dredged sludge. Approximate 5 million m² dredging area contained a mixture of organic and inorganic materials, industrial residues, and saltwater contaminants, all of which posed significant dewatering complexities. A total of approximately 3,500 GEOTUBE units are expected to be used throughout the project, making it essential to optimize polymer selection to achieve the desired dry solid content of at least 60 percent.

Another logistical challenge was the project's proximity to the densely populated city of Kocaeli, home to nearly two million residents. The continuous transportation of dredged material and construction equipment required careful coordination to minimize disruptions to local traffic and infrastructure. Additionally, coastal location presented environmental and operational hurdles, such as exposure to corrosive saltwater and the need to protect sensitive marine habitats from unintended ecological disturbances.

The dewatering process itself required precise calibration of polymer dosing to ensure efficient flocculation across different sludge compositions. Salty seawater added another layer of complexity, as standard polymer formulations were not always effective in achieving optimal dewatering performance.

The installation process for this large-scale dewatering operation involved deployment of GEOTUBE units over a 60,000 m² dewatering area lined with GSE^® HD geomembrane to prevent contamination. Flocculated sludge is pumped into the tubes, allowing the water to separate and dissipate while retaining the solid waste within the tubes. Clarified effluent is returned to the sea, ensuring minimal environmental disruption.

Solution

To address these challenges, Solmax collaborated with Istanbul University to design an optimized dewatering laydown area tailored to the project's large-scale requirements. GEOTUBE units were specifically chosen for their proven ability to handle high volumes of sludge while maintaining structural integrity under varying dewatering conditions.

A key aspect of the project's success was the development of customized polymer formulations to enhance the dewatering efficiency of the GEOTUBE units. Multiple polymer trials were conducted to determine the most effective combinations for different sludge compositions, ensuring that the target dry solid content was consistently met. The use of advanced polymer dosing systems allowed for real-time adjustments based on the sludge characteristics, improving overall efficiency.

In terms of material selection, the project utilized approximately 3,500 GEOTUBE units, 18,000 m² of MIRAGRID^® GX 80/80 geogrids, and an extensive GSE HD geomembrane lining system to create a robust dewatering infrastructure. GEOTUBE units employed in the project were CE-certified and had a track record of successful performance in similar applications, further reinforcing confidence in their reliability.

The project team implemented strategic transportation planning to mitigate the impact on local traffic. Deliveries of GEOTUBE units and other materials were scheduled during off-peak hours, and designated routes were established to minimize congestion in urban areas. The use of booster pumps to maintain pressure in the dredging system helped streamline sludge transfer operations, reducing downtime and improving efficiency.

Within a few weeks, approximately 150 units measuring 27.4 by 30 m were delivered to the site, demonstrating the feasibility of executing large-scale dewatering operations within tight timelines. This efficiency was critical in ensuring that dredging and dewatering processes remained on schedule, preventing any potential delays that could exacerbate environmental concerns in the Marmara Sea.

GEOTUBE units provided a practical and cost-effective solution for sludge dewatering in challenging environments. The ability to manage diverse sludge compositions, handle high volumes of material, and operate efficiently in a coastal setting underscores the versatility and scalability of this technology.

The successful removal of contaminated sludge from Kocaeli Bay will contribute to the long-term restoration of the Marmara Sea's ecological balance, benefiting local communities, marine biodiversity, and regional economic activities such as tourism and fishing. The project highlights the importance of integrating geosynthetic solutions into large-scale environmental remediation efforts and reinforces the critical role of GEOTUBE technology in sustainable dredging and dewatering applications.